Expand --report-current to show partitions and all mounts (except pseudo-filesystems)

Standardize 2-copy bcachefs topology naming to 'bcachefs-2copy' across code and docs; align parser and Display; update docs and ADR
config: reuse reserved label and GPT name constants
2025-10-20 14:55:38 +02:00 · 2025-10-20 14:21:47 +02:00 · 2025-10-13 10:35:31 +02:00 · 2025-10-10 14:49:39 +02:00 · 2025-10-10 14:11:52 +02:00 · 2025-10-10 10:11:58 +02:00
37 changed files with 6746 additions and 1034 deletions
--- a/PROMPT.md
+++ b/PROMPT.md
@@ -24,7 +24,7 @@ Device Discovery

 Partitioning Requirements
 - Use GPT exclusively. Honor 1 MiB alignment boundaries.
- For BIOS compatibility, create a small `bios_boot` partition (exact size TBD—assume 1 MiB for now, placed first).
+- For BIOS compatibility on BIOS systems, create a small `bios_boot` partition (size 1 MiB, placed first). When running under UEFI (`/sys/firmware/efi` present), the BIOS boot partition is suppressed.
 - Create a 512 MiB FAT32 ESP on each disk, label `ZOSBOOT`. Each ESP is independent; synchronization will be handled by another tool (out of scope). Ensure unique partition UUIDs while keeping identical labels.
 - Remaining disk capacity is provisioned per configuration (see below).
 - Before making changes, verify the device has no existing partitions or filesystem signatures; abort otherwise.
@@ -51,11 +51,11 @@ Filesystem Provisioning

 Configuration Input
 - Accept configuration via:
-  * Kernel command line parameter (name TBD, e.g., `zosstorage.config=`) pointing to a YAML configuration descriptor.
-  * Optional CLI flags when run in user space (must mirror kernel cmdline semantics).
-  * On-disk YAML config file (default path TBD, e.g., `/etc/zosstorage/config.yaml`).
- Establish clear precedence: kernel cmdline overrides CLI arguments, which override config file defaults. No interactive prompts inside initramfs.
- YAML schema must at least describe disk selection rules, desired filesystem layout, boot partition preferences, filesystem options, mount targets, and logging verbosity. Document the schema and provide validation.
+  * Kernel command line parameter `zosstorage.config=` pointing to a YAML configuration descriptor.
+  * Optional CLI flags when run in user space (mirror kernel cmdline semantics).
+  * On-disk YAML config file (default path `/etc/zosstorage/config.yaml`).
+- Precedence: kernel cmdline overrides CLI arguments, which override config file, which override built-in defaults. No interactive prompts inside initramfs.
+- YAML schema must describe disk selection rules, desired filesystem layout, boot partition preferences, filesystem options, mount targets, and logging verbosity. See [docs/SCHEMA.md](docs/SCHEMA.md) and [src/types.rs](src/types.rs:1).

 State Reporting
 - After successful provisioning, emit a JSON state report (path TBD, e.g., `/run/zosstorage/state.json`) capturing:
@@ -70,7 +70,7 @@ Logging
 - By default, logs go to stderr; design for optional redirection to a file (path TBD). Avoid using `println!`.

 System Integration
- Decide whether to generate `/etc/fstab` entries; if enabled, produce deterministic ordering and documentation. Otherwise, document alternative mount management.
+- `/etc/fstab` generation: optional via CLI/config. When enabled, write only the four final subvolume/subdir mount entries (system, etc, modules, vm-meta) with `UUID=` sources in deterministic order. Root mounts under `/var/mounts/{UUID}` are runtime-only and excluded from fstab.
 - After provisioning, ensure the initramfs can mount the new filesystems (e.g., call `udevadm settle` if necessary). No external services are invoked.
 - No responsibility for updating `vmlinuz.efi`; another subsystem handles kernel updates.

@@ -95,11 +95,17 @@ Documentation & Deliverables
 - Include architectural notes describing module boundaries (device discovery, partitioning, filesystem provisioning, config parsing, logging, reporting).

 Open Items (call out explicitly)
- Exact sizes and ordering for `bios_boot` partition awaiting confirmation; note assumptions in code and documentation.
- Mount point naming scheme under `/var/cache` (per-UUID vs. config-defined) still to be finalized.
- Filesystem-specific tuning parameters (compression, RAID values, `bcachefs` options) require explicit defaults from stakeholders.
- Path/location for YAML config, kernel cmdline key, JSON report path, and optional log file path need final confirmation.
- Decision whether `/etc/fstab` is generated remains pending.
+- BIOS vs UEFI: `bios_boot` partition size fixed at 1 MiB and created only on BIOS systems; suppressed under UEFI (`/sys/firmware/efi` present).
+- Mount scheme finalized:
+  - Root mounts for each data filesystem at `/var/mounts/{UUID}` (runtime only).
+  - Final subvolume/subdir mounts from the primary data filesystem to `/var/cache/{system,etc,modules,vm-meta}`.
+- Filesystem-specific tuning parameters (compression, RAID values, `bcachefs` options) remain open for refinement; sensible defaults applied.
+- Config paths and keys stabilized:
+  - Kernel cmdline key: `zosstorage.config=`
+  - Default config file: `/etc/zosstorage/config.yaml`
+  - Default report path: `/run/zosstorage/state.json`
+  - Optional log file: `/run/zosstorage/zosstorage.log`
+- `/etc/fstab` generation policy decided: optional flag; writes only the four final subvolume/subdir entries.

 Implementation Constraints
 - Stick to clear module boundaries. Provide unit tests where possible (e.g., config parsing, device filtering).
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@

 One-shot disk provisioning utility intended for initramfs. It discovers eligible disks, plans a GPT layout based on a chosen topology, creates filesystems, mounts them under a predictable scheme, and emits a machine-readable report. Safe-by-default with a non-destructive preview mode.

-Status: first-draft preview capable. Partition apply, mkfs, and mounts are gated until the planning is validated in your environment.
+Status: apply mode implemented. Partition application (sgdisk), filesystem creation (vfat/btrfs/bcachefs), mount scheme with subvolumes, and optional fstab writing are available. Preview mode remains supported.

 Key modules
 - CLI and entrypoint:
@@ -20,21 +20,22 @@ Key modules
  - [src/partition/plan.rs](src/partition/plan.rs)
 - Filesystem planning/creation and mkfs integration:
  - [src/fs/plan.rs](src/fs/plan.rs)
- Mount planning and application (skeleton):
+- Mount planning and application:
  - [src/mount/ops.rs](src/mount/ops.rs)

 Features at a glance
- Topology-driven planning with built-in defaults: BtrfsSingle, BcachefsSingle, DualIndependent, Bcachefs2Copy, BtrfsRaid1, SsdHddBcachefs
- Non-destructive preview: --show/--report outputs JSON summary (disks, partition plan, filesystems, planned mountpoints)
+- Topology auto-selection with built-in defaults; optional kernel cmdline override via `zosstorage.topology=` (see ADR-0002)
+- Non-destructive preview: `--show`/`--report` outputs JSON summary (disks, partition plan, filesystems, planned mountpoints)
 - Safe discovery: excludes removable media by default (USB sticks) unless explicitly allowed
- Config-optional: the tool runs without any YAML; sensible defaults are always present and may be overridden/merged by config
+- No external YAML configuration; defaults-only per ADR-0002 (sane built-ins, topology may be overridden by kernel cmdline)

 Requirements
 - Linux with /proc and /sys mounted (initramfs friendly)
 - External tools discovered at runtime:
  - blkid (for probing UUIDs and signatures)
-  - sgdisk (for GPT application) — planned
-  - mkfs.vfat, mkfs.btrfs, bcachefs (for formatting) — invoked by fs/plan when enabled in execution phase
+  - sgdisk (for GPT application)
+  - mkfs.vfat, mkfs.btrfs, bcachefs (for formatting)
+  - udevadm (optional; for settle after partitioning)
 - Tracing/logging to stderr by default; optional file at /run/zosstorage/zosstorage.log

 Install and build
@@ -44,8 +45,6 @@ Install and build
 Binary is target/release/zosstorage.

 CLI usage
- Topology selection (config optional):
-  -t, --topology btrfs-single|bcachefs-single|dual-independent|bcachefs-2copy|btrfs-raid1|ssd-hdd-bcachefs
 - Preview (non-destructive):
  --show                      Print JSON summary to stdout
  --report PATH               Write JSON summary to a file
@@ -55,19 +54,30 @@ CLI usage
  -l, --log-level LEVEL       error|warn|info|debug (default: info)
  -L, --log-to-file           Also write logs to /run/zosstorage/zosstorage.log
 - Other:
-  -c, --config PATH           Merge a YAML config file (overrides defaults)
  -s, --fstab                 Enable writing /etc/fstab entries (when mounts are applied)
+  -a, --apply                 Perform partitioning, filesystem creation, and mounts (destructive)
  -f, --force                 Present but not implemented (returns an error)

+Deprecated (ignored with warning; see ADR-0002)
+  -t, --topology VALUE        Ignored; use kernel cmdline `zosstorage.topology=` instead
+  -c, --config PATH           Ignored; external YAML configuration is not used at runtime
+
 Examples
- Single disk plan with debug logs:
-  sudo ./zosstorage --show -t btrfs-single -l debug
- RAID1 btrfs across two disks; print and write summary:
-  sudo ./zosstorage --show --report /run/zosstorage/plan.json -t btrfs-raid1 -l debug -L
- SSD+HDD bcachefs plan, include removable devices (for lab cases):
-  sudo ./zosstorage --show -t ssd-hdd-bcachefs --allow-removable -l debug
+- Single disk plan with debug logs (defaults to btrfs_single automatically):
+  sudo ./zosstorage --show -l debug
+- Two-disk plan (defaults to dual_independent automatically), write summary:
+  sudo ./zosstorage --show --report /run/zosstorage/plan.json -l debug -L
+- Include removable devices for lab scenarios:
+  sudo ./zosstorage --show --allow-removable -l debug
 - Quiet plan to file:
-  sudo ./zosstorage --report /run/zosstorage/plan.json -t dual-independent
+  sudo ./zosstorage --report /run/zosstorage/plan.json
+- Apply single-disk plan (DESTRUCTIVE; wipes target disk; defaults select topology automatically):
+  sudo ./zosstorage --apply
+
+Kernel cmdline override (at boot)
+- To force a topology, pass one of:
+  zosstorage.topology=btrfs-single | bcachefs-single | dual-independent | btrfs-raid1 | ssd-hdd-bcachefs | bcachefs-2copy
+- The override affects only topology; all other settings use sane built-in defaults.

 Preview JSON shape (examples)
 1) Already provisioned (idempotency success):
@@ -107,14 +117,15 @@ Preview JSON shape (examples)
    }
  ],
  "filesystems_planned": [
-    { "kind": "vfat", "from_roles": ["esp"], "label": "ZOSBOOT", "planned_mountpoint": null },
-    { "kind": "btrfs", "from_roles": ["data"], "devices_planned": 2, "label": "ZOSDATA", "planned_mountpoint_template": "/var/cache/{UUID}" }
+    { "kind": "vfat", "from_roles": ["esp"], "label": "ZOSBOOT" },
+    { "kind": "btrfs", "from_roles": ["data"], "devices_planned": 2, "label": "ZOSDATA" }
  ],
  "mount": {
    "scheme": "per_uuid",
    "base_dir": "/var/cache",
    "fstab_enabled": false,
-    "target_template": "/var/cache/{UUID}"
+    "root_mount_template": "/var/mounts/{UUID}",
+    "final_targets": ["/var/cache/system", "/var/cache/etc", "/var/cache/modules", "/var/cache/vm-meta"]
  }
 }

--- a/config/zosstorage.example.yaml
+++ b/config/zosstorage.example.yaml
@@ -1,185 +0,0 @@
-# zosstorage example configuration (full surface)
-# Copy to /etc/zosstorage/config.yaml on the target system, or pass with:
-#   - CLI:   --config /path/to/your.yaml
-#   - Kernel cmdline: zosstorage.config=/path/to/your.yaml
-# Precedence (highest to lowest):
-#   kernel cmdline > CLI flags > CLI --config file > /etc/zosstorage/config.yaml > built-in defaults
-
-version: 1
-
-# -----------------------------------------------------------------------------
-# Logging
-# -----------------------------------------------------------------------------
-logging:
-  # one of: error, warn, info, debug
-  level: info
-  # when true, also logs to /run/zosstorage/zosstorage.log in initramfs
-  to_file: false
-
-# -----------------------------------------------------------------------------
-# Device selection rules
-# - include_patterns: device paths that are considered
-# - exclude_patterns: device paths to filter out
-# - allow_removable: future toggle for removable media (kept false by default)
-# - min_size_gib: ignore devices smaller than this size
-# -----------------------------------------------------------------------------
-device_selection:
-  include_patterns:
-    - "^/dev/sd\\w+$"
-    - "^/dev/nvme\\w+n\\d+$"
-    - "^/dev/vd\\w+$"
-  exclude_patterns:
-    - "^/dev/ram\\d+$"
-    - "^/dev/zram\\d+$"
-    - "^/dev/loop\\d+$"
-    - "^/dev/fd\\d+$"
-  allow_removable: false
-  min_size_gib: 10
-
-# -----------------------------------------------------------------------------
-# Desired topology (choose ONE)
-#   single             : Single eligible disk; btrfs on data
-#   dual_independent   : Two disks; independent btrfs on each
-#   ssd_hdd_bcachefs   : SSD + HDD; bcachefs with SSD as cache/promote and HDD backing
-#   btrfs_raid1        : Optional mirrored btrfs across two disks (only when explicitly requested)
-# -----------------------------------------------------------------------------
-topology:
-  mode: single
-  # mode: dual_independent
-  # mode: ssd_hdd_bcachefs
-  # mode: btrfs_raid1
-
-# -----------------------------------------------------------------------------
-# Partitioning (GPT only)
-# Reserved GPT names:
-#   - bios boot  : "zosboot" (tiny BIOS boot partition, non-FS)
-#   - ESP        : "zosboot" (FAT32)
-#   - Data       : "zosdata"
-#   - Cache      : "zoscache" (only for ssd_hdd_bcachefs)
-# Reserved filesystem labels:
-#   - ESP        : ZOSBOOT
-#   - Data (all filesystems including bcachefs): ZOSDATA
-# -----------------------------------------------------------------------------
-partitioning:
-  # 1 MiB alignment
-  alignment_mib: 1
-
-  # Abort if any target disk is not empty (required for safety)
-  require_empty_disks: true
-
-  bios_boot:
-    enabled: true
-    size_mib: 1
-    gpt_name: zosboot
-
-  esp:
-    size_mib: 512
-    label: ZOSBOOT
-    gpt_name: zosboot
-
-  data:
-    gpt_name: zosdata
-
-  # Only used in ssd_hdd_bcachefs
-  cache:
-    gpt_name: zoscache
-
-# -----------------------------------------------------------------------------
-# Filesystem options and tuning
-# All data filesystems (btrfs or bcachefs) use label ZOSDATA
-# ESP uses label ZOSBOOT
-# -----------------------------------------------------------------------------
-filesystem:
-  btrfs:
-    # Reserved; must be "ZOSDATA"
-    label: ZOSDATA
-    # e.g., "zstd:3", "zstd:5"
-    compression: zstd:3
-    # "none" | "raid1" (raid1 typically when topology.mode == btrfs_raid1)
-    raid_profile: none
-
-  bcachefs:
-    # Reserved; must be "ZOSDATA"
-    label: ZOSDATA
-    # "promote" (default) or "writeback" if supported by environment
-    cache_mode: promote
-    # Compression algorithm, e.g., "zstd"
-    compression: zstd
-    # Checksum algorithm, e.g., "crc32c"
-    checksum: crc32c
-
-  vfat:
-    # Reserved; must be "ZOSBOOT"
-    label: ZOSBOOT
-
-# -----------------------------------------------------------------------------
-# Mount scheme and optional fstab
-# Default behavior mounts data filesystems under /var/cache/<UUID>
-# -----------------------------------------------------------------------------
-mount:
-  # Base directory for mounts
-  base_dir: /var/cache
-  # Scheme: per_uuid | custom (custom reserved for future)
-  scheme: per_uuid
-  # When true, zosstorage will generate /etc/fstab entries in deterministic order
-  fstab_enabled: false
-
-# -----------------------------------------------------------------------------
-# Report output
-# JSON report is written after successful provisioning
-# -----------------------------------------------------------------------------
-report:
-  path: /run/zosstorage/state.json
-
-# -----------------------------------------------------------------------------
-# Examples for different topologies (uncomment and set topology.mode accordingly)
-# -----------------------------------------------------------------------------
-
-# Example: single disk (uses btrfs on data)
-# topology:
-#   mode: single
-# filesystem:
-#   btrfs:
-#     label: ZOSDATA
-#     compression: zstd:3
-#     raid_profile: none
-
-# Example: dual independent btrfs (two disks)
-# topology:
-#   mode: dual_independent
-# filesystem:
-#   btrfs:
-#     label: ZOSDATA
-#     compression: zstd:5
-#     raid_profile: none
-
-# Example: SSD + HDD with bcachefs
-# topology:
-#   mode: ssd_hdd_bcachefs
-# partitioning:
-#   cache:
-#     gpt_name: zoscache
-# filesystem:
-#   bcachefs:
-#     label: ZOSDATA
-#     cache_mode: promote
-#     compression: zstd
-#     checksum: crc32c
-
-# Example: btrfs RAID1 (two disks)
-# topology:
-#   mode: btrfs_raid1
-# filesystem:
-#   btrfs:
-#     label: ZOSDATA
-#     compression: zstd:3
-#     raid_profile: raid1
-
-# -----------------------------------------------------------------------------
-# Notes:
-# - Never modify devices outside include_patterns or inside exclude_patterns.
-# - Idempotency: if expected GPT names and filesystem labels are already present,
-#   zosstorage exits success without making changes.
-# - --force flag is reserved and not implemented; will return an "unimplemented" error.
-# - Kernel cmdline data: URLs for zosstorage.config= are currently unimplemented.
-# -----------------------------------------------------------------------------
--- a/docs/API-SKELETONS.md
+++ b/docs/API-SKELETONS.md
@@ -6,34 +6,34 @@ Purpose
 - After approval, these will be created in the src tree in Code mode.

 Index
- [src/lib.rs](src/lib.rs)
- [src/errors.rs](src/errors.rs)
- [src/main.rs](src/main.rs)
- [src/cli/args.rs](src/cli/args.rs)
- [src/logging/mod.rs](src/logging/mod.rs)
- [src/types.rs](src/types.rs)
- [src/config/loader.rs](src/config/loader.rs)
- [src/device/discovery.rs](src/device/discovery.rs)
- [src/partition/plan.rs](src/partition/plan.rs)
- [src/fs/plan.rs](src/fs/plan.rs)
- [src/mount/ops.rs](src/mount/ops.rs)
- [src/report/state.rs](src/report/state.rs)
- [src/orchestrator/run.rs](src/orchestrator/run.rs)
- [src/idempotency/mod.rs](src/idempotency/mod.rs)
- [src/util/mod.rs](src/util/mod.rs)
+- [src/lib.rs](../src/lib.rs)
+- [src/errors.rs](../src/errors.rs)
+- [src/main.rs](../src/main.rs)
+- [src/cli/args.rs](../src/cli/args.rs)
+- [src/logging/mod.rs](../src/logging/mod.rs)
+- [src/types.rs](../src/types.rs)
+- [src/config/loader.rs](../src/config/loader.rs)
+- [src/device/discovery.rs](../src/device/discovery.rs)
+- [src/partition/plan.rs](../src/partition/plan.rs)
+- [src/fs/plan.rs](../src/fs/plan.rs)
+- [src/mount/ops.rs](../src/mount/ops.rs)
+- [src/report/state.rs](../src/report/state.rs)
+- [src/orchestrator/run.rs](../src/orchestrator/run.rs)
+- [src/idempotency/mod.rs](../src/idempotency/mod.rs)
+- [src/util/mod.rs](../src/util/mod.rs)

 Conventions
- Shared [type Result<T>](src/errors.rs:1) and [enum Error](src/errors.rs:1).
+- Shared [type Result<T>](../src/errors.rs:1) and [enum Error](../src/errors.rs:1).
 - No stdout prints; use tracing only.
- External tools invoked via [util](src/util/mod.rs) wrappers.
+- External tools invoked via [util](../src/util/mod.rs) wrappers.

 ---

 ## Crate root

 References
- [src/lib.rs](src/lib.rs)
- [type Result<T> = std::result::Result<T, Error>](src/errors.rs:1)
+- [src/lib.rs](../src/lib.rs)
+- [type Result<T> = std::result::Result<T, Error>](../src/errors.rs:1)

 Skeleton (for later implementation in code mode)
 ```rust
@@ -63,8 +63,8 @@ pub const VERSION: &str = env!("CARGO_PKG_VERSION");
 ## Errors

 References
- [enum Error](src/errors.rs:1)
- [type Result<T>](src/errors.rs:1)
+- [enum Error](../src/errors.rs:1)
+- [type Result<T>](../src/errors.rs:1)

 Skeleton
 ```rust
@@ -107,8 +107,8 @@ pub type Result<T> = std::result::Result<T, Error>;
 ## Entrypoint

 References
- [fn main()](src/main.rs:1)
- [fn run(ctx: &Context) -> Result<()>](src/orchestrator/run.rs:1)
+- [fn main()](../src/main.rs:1)
+- [fn run(ctx: &Context) -> Result<()>](../src/orchestrator/run.rs:1)

 Skeleton
 ```rust
@@ -143,8 +143,8 @@ fn real_main() -> Result<()> {
 ## CLI

 References
- [struct Cli](src/cli/args.rs:1)
- [fn from_args() -> Cli](src/cli/args.rs:1)
+- [struct Cli](../src/cli/args.rs:1)
+- [fn from_args() -> Cli](../src/cli/args.rs:1)

 Skeleton
 ```rust
@@ -170,6 +170,18 @@ pub struct Cli {
    #[arg(long = "fstab", default_value_t = false)]
    pub fstab: bool,

+    /// Print preview JSON to stdout (non-destructive)
+    #[arg(long = "show", default_value_t = false)]
+    pub show: bool,
+
+    /// Write preview JSON to a file (non-destructive)
+    #[arg(long = "report")]
+    pub report: Option<String>,
+
+    /// Perform partitioning, filesystem creation, and mounts (DESTRUCTIVE)
+    #[arg(long = "apply", default_value_t = false)]
+    pub apply: bool,
+
    /// Present but non-functional; returns unimplemented error
    #[arg(long = "force")]
    pub force: bool,
@@ -186,8 +198,8 @@ pub fn from_args() -> Cli {
 ## Logging

 References
- [struct LogOptions](src/logging/mod.rs:1)
- [fn init_logging(opts: &LogOptions) -> Result<()>](src/logging/mod.rs:1)
+- [struct LogOptions](../src/logging/mod.rs:1)
+- [fn init_logging(opts: &LogOptions) -> Result<()>](../src/logging/mod.rs:1)

 Skeleton
 ```rust
@@ -218,13 +230,13 @@ pub fn init_logging(opts: &LogOptions) -> Result<()> {
 ## Configuration types

 References
- [struct Config](src/types.rs:1)
- [enum Topology](src/types.rs:1)
- [struct DeviceSelection](src/types.rs:1)
- [struct Partitioning](src/types.rs:1)
- [struct FsOptions](src/types.rs:1)
- [struct MountScheme](src/types.rs:1)
- [struct ReportOptions](src/types.rs:1)
+- [struct Config](../src/types.rs:1)
+- [enum Topology](../src/types.rs:1)
+- [struct DeviceSelection](../src/types.rs:1)
+- [struct Partitioning](../src/types.rs:1)
+- [struct FsOptions](../src/types.rs:1)
+- [struct MountScheme](../src/types.rs:1)
+- [struct ReportOptions](../src/types.rs:1)

 Skeleton
 ```rust
@@ -247,8 +259,10 @@ pub struct DeviceSelection {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 #[serde(rename_all = "snake_case")]
 pub enum Topology {
-    Single,
+    BtrfsSingle,
+    BcachefsSingle,
    DualIndependent,
+    Bcachefs2Copy,
    SsdHddBcachefs,
    BtrfsRaid1,
 }
@@ -351,8 +365,8 @@ pub struct Config {
 ## Configuration I/O

 References
- [fn load_and_merge(cli: &Cli) -> Result<Config>](src/config/loader.rs:1)
- [fn validate(cfg: &Config) -> Result<()>](src/config/loader.rs:1)
+- [fn load_and_merge(cli: &Cli) -> Result<Config>](../src/config/loader.rs:1)
+- [fn validate(cfg: &Config) -> Result<()>](../src/config/loader.rs:1)

 Skeleton
 ```rust
@@ -374,10 +388,10 @@ pub fn validate(cfg: &crate::config::types::Config) -> Result<()> {
 ## Device discovery

 References
- [struct Disk](src/device/discovery.rs:1)
- [struct DeviceFilter](src/device/discovery.rs:1)
- [trait DeviceProvider](src/device/discovery.rs:1)
- [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](src/device/discovery.rs:1)
+- [struct Disk](../src/device/discovery.rs:1)
+- [struct DeviceFilter](../src/device/discovery.rs:1)
+- [trait DeviceProvider](../src/device/discovery.rs:1)
+- [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](../src/device/discovery.rs:1)

 Skeleton
 ```rust
@@ -418,12 +432,12 @@ pub fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>> {
 ## Partitioning

 References
- [enum PartRole](src/partition/plan.rs:1)
- [struct PartitionSpec](src/partition/plan.rs:1)
- [struct PartitionPlan](src/partition/plan.rs:1)
- [struct PartitionResult](src/partition/plan.rs:1)
- [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](src/partition/plan.rs:1)
- [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](src/partition/plan.rs:1)
+- [enum PartRole](../src/partition/plan.rs:1)
+- [struct PartitionSpec](../src/partition/plan.rs:1)
+- [struct PartitionPlan](../src/partition/plan.rs:1)
+- [struct PartitionResult](../src/partition/plan.rs:1)
+- [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](../src/partition/plan.rs:1)
+- [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](../src/partition/plan.rs:1)

 Skeleton
 ```rust
@@ -485,12 +499,12 @@ pub fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>> {
 ## Filesystems

 References
- [enum FsKind](src/fs/plan.rs:1)
- [struct FsSpec](src/fs/plan.rs:1)
- [struct FsPlan](src/fs/plan.rs:1)
- [struct FsResult](src/fs/plan.rs:1)
- [fn plan_filesystems(...)](src/fs/plan.rs:1)
- [fn make_filesystems(...)](src/fs/plan.rs:1)
+- [enum FsKind](../src/fs/plan.rs:1)
+- [struct FsSpec](../src/fs/plan.rs:1)
+- [struct FsPlan](../src/fs/plan.rs:1)
+- [struct FsResult](../src/fs/plan.rs:1)
+- [fn plan_filesystems(...)](../src/fs/plan.rs:1)
+- [fn make_filesystems(...)](../src/fs/plan.rs:1)

 Skeleton
 ```rust
@@ -531,8 +545,8 @@ pub fn plan_filesystems(
    todo!("map ESP to vfat, data to btrfs or bcachefs according to topology")
 }

-/// Create the filesystems and return identity info (UUIDs, labels).
-pub fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>> {
+//// Create the filesystems and return identity info (UUIDs, labels).
+pub fn make_filesystems(plan: &FsPlan, cfg: &Config) -> Result<Vec<FsResult>> {
    todo!("invoke mkfs tools with configured options via util::run_cmd")
 }
 ```
@@ -542,11 +556,11 @@ pub fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>> {
 ## Mounting

 References
- [struct MountPlan](src/mount/ops.rs:1)
- [struct MountResult](src/mount/ops.rs:1)
- [fn plan_mounts(...)](src/mount/ops.rs:1)
- [fn apply_mounts(...)](src/mount/ops.rs:1)
- [fn maybe_write_fstab(...)](src/mount/ops.rs:1)
+- [struct MountPlan](../src/mount/ops.rs:1)
+- [struct MountResult](../src/mount/ops.rs:1)
+- [fn plan_mounts(...)](../src/mount/ops.rs:1)
+- [fn apply_mounts(...)](../src/mount/ops.rs:1)
+- [fn maybe_write_fstab(...)](../src/mount/ops.rs:1)

 Skeleton
 ```rust
@@ -565,9 +579,13 @@ pub struct MountResult {
    pub options: String,
 }

-/// Build mount plan under /var/cache/<UUID> by default.
+//// Build mount plan:
+//// - Root-mount all data filesystems under `/var/mounts/{UUID}` (runtime only)
+//// - Ensure/create subvolumes on the primary data filesystem: system, etc, modules, vm-meta
+//// - Plan final mounts to `/var/cache/{system,etc,modules,vm-meta}` using
+////   `subvol=` for btrfs and `X-mount.subdir=` for bcachefs.
 pub fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan> {
-    todo!("create per-UUID directories and mount mapping")
+    todo!("root mounts under /var/mounts/{UUID}; final subvol/subdir mounts to /var/cache/{system,etc,modules,vm-meta}")
 }

 /// Apply mounts using syscalls (nix), ensuring directories exist.
@@ -575,9 +593,12 @@ pub fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>> {
    todo!("perform mount syscalls and return results")
 }

-/// Optionally generate /etc/fstab entries in deterministic order.
+//// Optionally generate /etc/fstab entries for final subvolume/subdir mounts only.
+//// - Write exactly four entries: system, etc, modules, vm-meta
+//// - Use UUID= sources; deterministic order by target path
+//// - Exclude runtime root mounts under `/var/mounts/{UUID}`
 pub fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()> {
-    todo!("when enabled, write fstab entries")
+    todo!("when enabled, write only the four final subvolume/subdir entries with UUID= sources")
 }
 ```

@@ -586,10 +607,10 @@ pub fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()> {
 ## Reporting

 References
- [const REPORT_VERSION: &str](src/report/state.rs:1)
- [struct StateReport](src/report/state.rs:1)
- [fn build_report(...)](src/report/state.rs:1)
- [fn write_report(...)](src/report/state.rs:1)
+- [const REPORT_VERSION: &str](../src/report/state.rs:1)
+- [struct StateReport](../src/report/state.rs:1)
+- [fn build_report(...)](../src/report/state.rs:1)
+- [fn write_report(...)](../src/report/state.rs:1)

 Skeleton
 ```rust
@@ -632,8 +653,8 @@ pub fn write_report(report: &StateReport, path: &str) -> Result<()> {
 ## Orchestrator

 References
- [struct Context](src/orchestrator/run.rs:1)
- [fn run(ctx: &Context) -> Result<()>](src/orchestrator/run.rs:1)
+- [struct Context](../src/orchestrator/run.rs:1)
+- [fn run(ctx: &Context) -> Result<()>](../src/orchestrator/run.rs:1)

 Skeleton
 ```rust
@@ -662,8 +683,8 @@ pub fn run(ctx: &Context) -> Result<()> {
 ## Idempotency

 References
- [fn detect_existing_state() -> Result<Option<StateReport>>](src/idempotency/mod.rs:1)
- [fn is_empty_disk(disk: &Disk) -> Result<bool>](src/idempotency/mod.rs:1)
+- [fn detect_existing_state() -> Result<Option<StateReport>>](../src/idempotency/mod.rs:1)
+- [fn is_empty_disk(disk: &Disk) -> Result<bool>](../src/idempotency/mod.rs:1)

 Skeleton
 ```rust
@@ -685,11 +706,11 @@ pub fn is_empty_disk(disk: &Disk) -> Result<bool> {
 ## Utilities

 References
- [struct CmdOutput](src/util/mod.rs:1)
- [fn which_tool(name: &str) -> Result<Option<String>>](src/util/mod.rs:1)
- [fn run_cmd(args: &[&str]) -> Result<()>](src/util/mod.rs:1)
- [fn run_cmd_capture(args: &[&str]) -> Result<CmdOutput>](src/util/mod.rs:1)
- [fn udev_settle(timeout_ms: u64) -> Result<()>](src/util/mod.rs:1)
+- [struct CmdOutput](../src/util/mod.rs:1)
+- [fn which_tool(name: &str) -> Result<Option<String>>](../src/util/mod.rs:1)
+- [fn run_cmd(args: &[&str]) -> Result<()>](../src/util/mod.rs:1)
+- [fn run_cmd_capture(args: &[&str]) -> Result<CmdOutput>](../src/util/mod.rs:1)
+- [fn udev_settle(timeout_ms: u64) -> Result<()>](../src/util/mod.rs:1)

 Skeleton
 ```rust
@@ -722,6 +743,11 @@ pub fn run_cmd_capture(args: &[&str]) -> Result<CmdOutput> {
 pub fn udev_settle(timeout_ms: u64) -> Result<()> {
    todo!("invoke udevadm settle when present")
 }
+
+/// Detect UEFI environment by checking /sys/firmware/efi; used to suppress BIOS boot partition on UEFI.
+pub fn is_efi_boot() -> bool {
+    todo!("return Path::new(\"/sys/firmware/efi\").exists()")
+}
 ```

 ---
@@ -735,24 +761,24 @@ Approval gate
  - Add initial tests scaffolding and example configs.

 References summary
- [fn main()](src/main.rs:1)
- [fn from_args()](src/cli/args.rs:1)
- [fn init_logging(opts: &LogOptions)](src/logging/mod.rs:1)
- [fn load_and_merge(cli: &Cli)](src/config/loader.rs:1)
- [fn validate(cfg: &Config)](src/config/loader.rs:1)
- [fn discover(filter: &DeviceFilter)](src/device/discovery.rs:1)
- [fn plan_partitions(disks: &[Disk], cfg: &Config)](src/partition/plan.rs:1)
- [fn apply_partitions(plan: &PartitionPlan)](src/partition/plan.rs:1)
- [fn plan_filesystems(parts: &[PartitionResult], cfg: &Config)](src/fs/plan.rs:1)
- [fn make_filesystems(plan: &FsPlan)](src/fs/plan.rs:1)
- [fn plan_mounts(fs_results: &[FsResult], cfg: &Config)](src/mount/ops.rs:1)
- [fn apply_mounts(plan: &MountPlan)](src/mount/ops.rs:1)
- [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config)](src/mount/ops.rs:1)
- [fn build_report(...)](src/report/state.rs:1)
- [fn write_report(report: &StateReport)](src/report/state.rs:1)
- [fn detect_existing_state()](src/idempotency/mod.rs:1)
- [fn is_empty_disk(disk: &Disk)](src/idempotency/mod.rs:1)
- [fn which_tool(name: &str)](src/util/mod.rs:1)
- [fn run_cmd(args: &[&str])](src/util/mod.rs:1)
- [fn run_cmd_capture(args: &[&str])](src/util/mod.rs:1)
- [fn udev_settle(timeout_ms: u64)](src/util/mod.rs:1)
+- [fn main()](../src/main.rs:1)
+- [fn from_args()](../src/cli/args.rs:1)
+- [fn init_logging(opts: &LogOptions)](../src/logging/mod.rs:1)
+- [fn load_and_merge(cli: &Cli)](../src/config/loader.rs:1)
+- [fn validate(cfg: &Config)](../src/config/loader.rs:1)
+- [fn discover(filter: &DeviceFilter)](../src/device/discovery.rs:1)
+- [fn plan_partitions(disks: &[Disk], cfg: &Config)](../src/partition/plan.rs:1)
+- [fn apply_partitions(plan: &PartitionPlan)](../src/partition/plan.rs:1)
+- [fn plan_filesystems(parts: &[PartitionResult], cfg: &Config)](../src/fs/plan.rs:1)
+- [fn make_filesystems(plan: &FsPlan)](../src/fs/plan.rs:1)
+- [fn plan_mounts(fs_results: &[FsResult], cfg: &Config)](../src/mount/ops.rs:1)
+- [fn apply_mounts(plan: &MountPlan)](../src/mount/ops.rs:1)
+- [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config)](../src/mount/ops.rs:1)
+- [fn build_report(...)](../src/report/state.rs:1)
+- [fn write_report(report: &StateReport)](../src/report/state.rs:1)
+- [fn detect_existing_state()](../src/idempotency/mod.rs:1)
+- [fn is_empty_disk(disk: &Disk)](../src/idempotency/mod.rs:1)
+- [fn which_tool(name: &str)](../src/util/mod.rs:1)
+- [fn run_cmd(args: &[&str])](../src/util/mod.rs:1)
+- [fn run_cmd_capture(args: &[&str])](../src/util/mod.rs:1)
+- [fn udev_settle(timeout_ms: u64)](../src/util/mod.rs:1)
--- a/docs/API.md
+++ b/docs/API.md
@@ -8,40 +8,40 @@ Conventions
 - External tooling calls are mediated via utility wrappers.

 Module index
- [src/main.rs](src/main.rs)
- [src/lib.rs](src/lib.rs)
- [src/errors.rs](src/errors.rs)
- [src/cli/args.rs](src/cli/args.rs)
- [src/logging/mod.rs](src/logging/mod.rs)
- [src/types.rs](src/types.rs)
- [src/config/loader.rs](src/config/loader.rs)
- [src/device/discovery.rs](src/device/discovery.rs)
- [src/partition/plan.rs](src/partition/plan.rs)
- [src/fs/plan.rs](src/fs/plan.rs)
- [src/mount/ops.rs](src/mount/ops.rs)
- [src/report/state.rs](src/report/state.rs)
- [src/orchestrator/run.rs](src/orchestrator/run.rs)
- [src/idempotency/mod.rs](src/idempotency/mod.rs)
- [src/util/mod.rs](src/util/mod.rs)
+- [src/main.rs](../src/main.rs)
+- [src/lib.rs](../src/lib.rs)
+- [src/errors.rs](../src/errors.rs)
+- [src/cli/args.rs](../src/cli/args.rs)
+- [src/logging/mod.rs](../src/logging/mod.rs)
+- [src/types.rs](../src/types.rs)
+- [src/config/loader.rs](../src/config/loader.rs)
+- [src/device/discovery.rs](../src/device/discovery.rs)
+- [src/partition/plan.rs](../src/partition/plan.rs)
+- [src/fs/plan.rs](../src/fs/plan.rs)
+- [src/mount/ops.rs](../src/mount/ops.rs)
+- [src/report/state.rs](../src/report/state.rs)
+- [src/orchestrator/run.rs](../src/orchestrator/run.rs)
+- [src/idempotency/mod.rs](../src/idempotency/mod.rs)
+- [src/util/mod.rs](../src/util/mod.rs)

 Common errors and result
- [enum Error](src/errors.rs:1)
+- [enum Error](../src/errors.rs:1)
  - Top-level error type covering parse/validation errors, device discovery errors, partitioning failures, filesystem mkfs errors, mount errors, report write errors, and external tool invocation failures with stderr capture.
- [type Result<T> = std::result::Result<T, Error>](src/errors.rs:1)
+- [type Result<T> = std::result::Result<T, Error>](../src/errors.rs:1)
  - Shared result alias across modules.

 Crate root
- [src/lib.rs](src/lib.rs)
+- [src/lib.rs](../src/lib.rs)
  - Exposes crate version constants, the prelude, and re-exports common types for consumers of the library (tests/integration). No heavy logic.

 Entrypoint
- [fn main()](src/main.rs:1)
+- [fn main()](../src/main.rs:1)
  - Initializes logging based on CLI defaults, parses CLI flags and kernel cmdline, loads and validates configuration, and invokes the orchestrator run sequence. Avoids stdout; logs via tracing only.

 Orchestrator
- [struct Context](src/orchestrator/run.rs:1)
+- [struct Context](../src/orchestrator/run.rs:1)
  - Aggregates resolved configuration, logging options, and environment flags suited for initramfs execution.
- [fn run(ctx: &Context) -> Result<()>](src/orchestrator/run.rs:1)
+- [fn run(ctx: &Context) -> Result<()>](../src/orchestrator/run.rs:1)
  - High-level one-shot flow:
    - Idempotency detection
    - Device discovery
@@ -52,131 +52,141 @@ Orchestrator
  - Aborts the entire run on any validation or execution failure. Returns Ok on successful no-op if already provisioned.

 CLI
- [struct Cli](src/cli/args.rs:1)
+- [struct Cli](../src/cli/args.rs:1)
  - Mirrors kernel cmdline semantics with flags:
    - --config PATH
    - --log-level LEVEL
    - --log-to-file
    - --fstab
+    - --show
+    - --report PATH
+    - --apply
    - --force (present, returns unimplemented error)
- [fn from_args() -> Cli](src/cli/args.rs:1)
+- [fn from_args() -> Cli](../src/cli/args.rs:1)
  - Parses argv without side effects; suitable for initramfs.

 Logging
- [struct LogOptions](src/logging/mod.rs:1)
+- [struct LogOptions](../src/logging/mod.rs:1)
  - Holds level and optional file target (/run/zosstorage/zosstorage.log).
- [fn init_logging(opts: &LogOptions) -> Result<()>](src/logging/mod.rs:1)
+- [fn init_logging(opts: &LogOptions) -> Result<()>](../src/logging/mod.rs:1)
  - Configures tracing-subscriber for stderr by default and optional file layer when enabled. Must be idempotent.

 Configuration types
- [struct Config](src/types.rs:1)
+- [struct Config](../src/types.rs:1)
  - The validated configuration used by the orchestrator, containing logging, device selection rules, topology, partitioning, filesystem options, mount scheme, and report path.
- [enum Topology](src/types.rs:1)
-  - Values: btrfs_single, bcachefs_single, dual_independent, bcachefs_2copy, ssd_hdd_bcachefs, btrfs_raid1 (opt-in).
- [struct DeviceSelection](src/types.rs:1)
+- [enum Topology](../src/types.rs:1)
+  - Values: btrfs_single, bcachefs_single, dual_independent, bcachefs-2copy, ssd_hdd_bcachefs, btrfs_raid1 (opt-in).
+- [struct DeviceSelection](../src/types.rs:1)
  - Include and exclude regex patterns, minimum size, removable policy.
- [struct Partitioning](src/types.rs:1)
+- [struct Partitioning](../src/types.rs:1)
  - Alignment, emptiness requirement, bios_boot, esp, data, cache GPT names and sizes where applicable.
- [struct BtrfsOptions](src/types.rs:1)
+- [struct BtrfsOptions](../src/types.rs:1)
  - Compression string and raid profile (none or raid1).
- [struct BcachefsOptions](src/types.rs:1)
+- [struct BcachefsOptions](../src/types.rs:1)
  - Cache mode (promote or writeback), compression, checksum.
- [struct VfatOptions](src/types.rs:1)
+- [struct VfatOptions](../src/types.rs:1)
  - Reserved for ESP mkfs options; includes label ZOSBOOT.
- [struct FsOptions](src/types.rs:1)
+- [struct FsOptions](../src/types.rs:1)
  - Aggregates BtrfsOptions, BcachefsOptions, VfatOptions and shared defaults such as ZOSDATA label.
- [enum MountSchemeKind](src/types.rs:1)
+- [enum MountSchemeKind](../src/types.rs:1)
  - Values: per_uuid, custom (future).
- [struct MountScheme](src/types.rs:1)
+- [struct MountScheme](../src/types.rs:1)
  - Base directory (/var/cache), scheme kind, fstab enabled flag.
- [struct ReportOptions](src/types.rs:1)
+- [struct ReportOptions](../src/types.rs:1)
  - Output path (/run/zosstorage/state.json).

 Configuration IO
- [fn load_and_merge(cli: &Cli) -> Result<Config>](src/config/loader.rs:1)
+- [fn load_and_merge(cli: &Cli) -> Result<Config>](../src/config/loader.rs:1)
  - Loads built-in defaults, optionally merges on-disk config, overlays CLI flags, and finally overlays kernel cmdline via zosstorage.config=. Validates the YAML against types and constraints.
- [fn validate(cfg: &Config) -> Result<()>](src/config/loader.rs:1)
+- [fn validate(cfg: &Config) -> Result<()>](../src/config/loader.rs:1)
  - Ensures structural and semantic validity (e.g., disk selection rules not empty, sizes non-zero, supported topology combinations).

 Device discovery
- [struct Disk](src/device/discovery.rs:1)
+- [struct Disk](../src/device/discovery.rs:1)
  - Represents an eligible block device with path, size, rotational flag, and identifiers (serial, model if available).
- [struct DeviceFilter](src/device/discovery.rs:1)
+- [struct DeviceFilter](../src/device/discovery.rs:1)
  - Derived from DeviceSelection; compiled regexes and size thresholds for efficient filtering.
- [trait DeviceProvider](src/device/discovery.rs:1)
+- [trait DeviceProvider](../src/device/discovery.rs:1)
  - Abstraction for listing /dev and probing properties, enabling test doubles.
- [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](src/device/discovery.rs:1)
+- [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](../src/device/discovery.rs:1)
  - Returns eligible disks or a well-defined error if none are found.

 Partitioning
- [enum PartRole](src/partition/plan.rs:1)
+- [enum PartRole](../src/partition/plan.rs:1)
  - Roles: BiosBoot, Esp, Data, Cache.
- [struct PartitionSpec](src/partition/plan.rs:1)
+- [struct PartitionSpec](../src/partition/plan.rs:1)
  - Declarative spec for a single partition: role, optional size_mib, gpt_name (zosboot, zosdata, zoscache), and reserved filesystem label when role is Esp (ZOSBOOT).
- [struct DiskPlan](src/partition/plan.rs:1)
+- [struct DiskPlan](../src/partition/plan.rs:1)
  - The planned set of PartitionSpec instances for a single Disk in the chosen topology.
- [struct PartitionPlan](src/partition/plan.rs:1)
+- [struct PartitionPlan](../src/partition/plan.rs:1)
  - Combined plan across all target disks, including alignment rules and safety checks.
- [struct PartitionResult](src/partition/plan.rs:1)
+- [struct PartitionResult](../src/partition/plan.rs:1)
  - Result of applying a DiskPlan: device path of each created partition, role, partition GUID, and gpt_name.
- [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](src/partition/plan.rs:1)
+- [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](../src/partition/plan.rs:1)
  - Produces a GPT-only plan with 1 MiB alignment, bios boot first (1 MiB), ESP 512 MiB, data remainder, and zoscache on SSD for ssd_hdd_bcachefs.
- [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](src/partition/plan.rs:1)
+- [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](../src/partition/plan.rs:1)
  - Executes the plan via sgdisk and related utilities. Aborts if target disks are not empty or if signatures are detected.

 Filesystems
- [enum FsKind](src/fs/plan.rs:1)
+- [enum FsKind](../src/fs/plan.rs:1)
  - Values: Vfat, Btrfs, Bcachefs.
- [struct FsSpec](src/fs/plan.rs:1)
+- [struct FsSpec](../src/fs/plan.rs:1)
  - Maps PartitionResult to desired filesystem kind and label (ZOSBOOT for ESP; ZOSDATA for all data filesystems including bcachefs).
- [struct FsPlan](src/fs/plan.rs:1)
+- [struct FsPlan](../src/fs/plan.rs:1)
  - Plan of mkfs operations across all partitions and devices given the topology.
- [struct FsResult](src/fs/plan.rs:1)
+- [struct FsResult](../src/fs/plan.rs:1)
  - Output of mkfs: device path(s), fs uuid, label, and kind.
- [fn plan_filesystems(disks: &[Disk], parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan>](src/fs/plan.rs:1)
+- [fn plan_filesystems(disks: &[Disk], parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan>](../src/fs/plan.rs:1)
  - Determines which partitions receive vfat, btrfs, or bcachefs, and aggregates tuning options.
- [fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>>](src/fs/plan.rs:1)
+- [fn make_filesystems(plan: &FsPlan, cfg: &Config) -> Result<Vec<FsResult>>](../src/fs/plan.rs:1)
  - Invokes mkfs.vfat, mkfs.btrfs, mkfs.bcachefs accordingly via utility wrappers and returns filesystem identities.

 Mounting
- [struct MountPlan](src/mount/ops.rs:1)
-  - Derived from FsResult entries: creates target directories under /var/cache/<UUID> and the mounts required for the current boot.
- [struct MountResult](src/mount/ops.rs:1)
+- [struct MountPlan](../src/mount/ops.rs:1)
+  - Derived from FsResult entries. Plans:
+    - Root mounts for all data filesystems under `/var/mounts/{UUID}` (runtime only).
+      - btrfs root options: `rw,noatime,subvolid=5`
+      - bcachefs root options: `rw,noatime`
+    - Final subvolume/subdir mounts (from the primary data filesystem) to:
+      - `/var/cache/system`, `/var/cache/etc`, `/var/cache/modules`, `/var/cache/vm-meta`
+- [struct MountResult](../src/mount/ops.rs:1)
  - Actual mount operations performed (source, target, fstype, options).
- [fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan>](src/mount/ops.rs:1)
-  - Translates filesystem identities to mount targets and options.
- [fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>>](src/mount/ops.rs:1)
-  - Performs mounts using syscalls (nix crate) with minimal dependencies. Ensures directories exist.
- [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()>](src/mount/ops.rs:1)
-  - When enabled, generates /etc/fstab entries in deterministic order. Disabled by default.
+- [fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan>](../src/mount/ops.rs:1)
+  - Translates filesystem identities to mount targets and options, including `subvol=` for btrfs and `X-mount.subdir=` for bcachefs.
+- [fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>>](../src/mount/ops.rs:1)
+  - Performs mounts using syscalls (nix crate). Ensures directories exist and creates subvolumes/subdirs if missing.
+- [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()>](../src/mount/ops.rs:1)
+  - When enabled, writes only the four subvolume/subdir mount entries to `/etc/fstab` in deterministic order using `UUID=` sources. Root mounts under `/var/mounts` are excluded.

 Reporting
- [const REPORT_VERSION: &str](src/report/state.rs:1)
+- [const REPORT_VERSION: &str](../src/report/state.rs:1)
  - Version string for the JSON payload schema.
- [struct StateReport](src/report/state.rs:1)
+- [struct StateReport](../src/report/state.rs:1)
  - Machine-readable state describing discovered disks, created partitions, filesystems, labels, mountpoints, status, and timestamp.
- [fn build_report(disks: &[Disk], parts: &[PartitionResult], fs: &[FsResult], mounts: &[MountResult], status: &str) -> StateReport](src/report/state.rs:1)
+- [fn build_report(disks: &[Disk], parts: &[PartitionResult], fs: &[FsResult], mounts: &[MountResult], status: &str) -> StateReport](../src/report/state.rs:1)
  - Constructs a StateReport matching REPORT_VERSION.
- [fn write_report(report: &StateReport) -> Result<()>](src/report/state.rs:1)
+- [fn write_report(report: &StateReport) -> Result<()>](../src/report/state.rs:1)
  - Writes JSON to /run/zosstorage/state.json (configurable).

 Idempotency
- [fn detect_existing_state() -> Result<Option<StateReport>>](src/idempotency/mod.rs:1)
+- [fn detect_existing_state() -> Result<Option<StateReport>>](../src/idempotency/mod.rs:1)
  - Probes for expected GPT names (zosboot, zosdata, zoscache where applicable) and filesystem labels (ZOSBOOT, ZOSDATA). If present and consistent, returns a StateReport; orchestrator exits success without changes.
- [fn is_empty_disk(disk: &Disk) -> Result<bool>](src/idempotency/mod.rs:1)
+- [fn is_empty_disk(disk: &Disk) -> Result<bool>](../src/idempotency/mod.rs:1)
  - Determines disk emptiness: absence of partitions and known filesystem signatures.

 Utilities
- [struct CmdOutput](src/util/mod.rs:1)
+- [struct CmdOutput](../src/util/mod.rs:1)
  - Captures status, stdout, stderr from external tool invocations.
- [fn which_tool(name: &str) -> Result<Option<String>>](src/util/mod.rs:1)
+- [fn which_tool(name: &str) -> Result<Option<String>>](../src/util/mod.rs:1)
  - Locates a required system utility in PATH, returning its absolute path if available.
- [fn run_cmd(args: &[&str]) -> Result<()>](src/util/mod.rs:1)
+- [fn run_cmd(args: &[&str]) -> Result<()>](../src/util/mod.rs:1)
  - Executes a command (args[0] is binary) and returns Ok when exit status is zero; logs stderr on failure.
- [fn run_cmd_capture(args: &[&str]) -> Result<CmdOutput>](src/util/mod.rs:1)
+- [fn run_cmd_capture(args: &[&str]) -> Result<CmdOutput>](../src/util/mod.rs:1)
  - Executes a command and returns captured output for parsing (e.g., blkid).
- [fn udev_settle(timeout_ms: u64) -> Result<()>](src/util/mod.rs:1)
+- [fn udev_settle(timeout_ms: u64) -> Result<()>](../src/util/mod.rs:1)
  - Calls udevadm settle with a timeout when available; otherwise no-ops with a warning.
+- [fn is_efi_boot() -> bool](../src/util/mod.rs:1)
+  - Detects UEFI environment by checking `/sys/firmware/efi`; used to suppress BIOS boot partition creation on UEFI systems.

 Behavioral notes and contracts
 - Safety and idempotency:
@@ -188,10 +198,13 @@ Behavioral notes and contracts
  - Data filesystems use label ZOSDATA regardless of backend kind.
  - Cache partitions in bcachefs topology use GPT name zoscache.
 - Topology-specific behavior:
-  - single: one data filesystem (btrfs) on the sole disk.
-  - dual_independent: two separate btrfs filesystems, one per disk.
+  - btrfs_single: one data filesystem (btrfs) on the sole disk.
+  - bcachefs_single: one data filesystem (bcachefs) on the sole disk.
+  - dual_independent: independent btrfs filesystems on each eligible disk (one or more).
+  - bcachefs-2copy: multi-device bcachefs across two or more data partitions with `--replicas=2` (data and metadata).
  - ssd_hdd_bcachefs: bcachefs spanning SSD (cache/promote) and HDD (backing), labeled ZOSDATA.
  - btrfs_raid1: only when explicitly requested; otherwise default to independent btrfs.
+- UEFI vs BIOS: when running under UEFI (`/sys/firmware/efi` present), the BIOS boot partition is suppressed.

 Module dependency overview

--- a/docs/ARCHITECTURE.md
+++ b/docs/ARCHITECTURE.md
@@ -30,116 +30,122 @@ Top level
  - [tests/integration_ssd_hdd.rs](tests/integration_ssd_hdd.rs)

 Crate sources
- [src/main.rs](src/main.rs)
- [src/lib.rs](src/lib.rs)
- [src/errors.rs](src/errors.rs)
- [src/cli/args.rs](src/cli/args.rs)
- [src/logging/mod.rs](src/logging/mod.rs)
- [src/config/loader.rs](src/config/loader.rs)
- [src/types.rs](src/types.rs)
- [src/device/discovery.rs](src/device/discovery.rs)
- [src/partition/plan.rs](src/partition/plan.rs)
- [src/fs/plan.rs](src/fs/plan.rs)
- [src/mount/ops.rs](src/mount/ops.rs)
- [src/report/state.rs](src/report/state.rs)
- [src/orchestrator/run.rs](src/orchestrator/run.rs)
- [src/idempotency/mod.rs](src/idempotency/mod.rs)
- [src/util/mod.rs](src/util/mod.rs)
+- [src/main.rs](../src/main.rs)
+- [src/lib.rs](../src/lib.rs)
+- [src/errors.rs](../src/errors.rs)
+- [src/cli/args.rs](../src/cli/args.rs)
+- [src/logging/mod.rs](../src/logging/mod.rs)
+- [src/config/loader.rs](../src/config/loader.rs)
+- [src/types.rs](../src/types.rs)
+- [src/device/discovery.rs](../src/device/discovery.rs)
+- [src/partition/plan.rs](../src/partition/plan.rs)
+- [src/fs/plan.rs](../src/fs/plan.rs)
+- [src/mount/ops.rs](../src/mount/ops.rs)
+- [src/report/state.rs](../src/report/state.rs)
+- [src/orchestrator/run.rs](../src/orchestrator/run.rs)
+- [src/idempotency/mod.rs](../src/idempotency/mod.rs)
+- [src/util/mod.rs](../src/util/mod.rs)

 Module responsibilities
- [src/main.rs](src/main.rs)
+- [src/main.rs](../src/main.rs)
  - Entrypoint. Parse CLI, initialize logging, load and merge configuration per precedence, call orchestrator. No stdout spam.
- [src/lib.rs](src/lib.rs)
+- [src/lib.rs](../src/lib.rs)
  - Crate exports, prelude, version constants, Result alias.
- [src/errors.rs](src/errors.rs)
+- [src/errors.rs](../src/errors.rs)
  - Common error enum and Result alias via thiserror.
- [src/cli/args.rs](src/cli/args.rs)
+- [src/cli/args.rs](../src/cli/args.rs)
  - CLI definition mirroring kernel cmdline semantics; provide non-interactive interface. Stub --force returns unimplemented.
- [src/logging/mod.rs](src/logging/mod.rs)
+- [src/logging/mod.rs](../src/logging/mod.rs)
  - Initialize tracing; levels error, warn, info, debug; default to stderr; optional file target.
- [src/config/loader.rs](src/config/loader.rs) and [src/types.rs](src/types.rs)
+- [src/config/loader.rs](../src/config/loader.rs) and [src/types.rs](../src/types.rs)
  - YAML schema types, validation, loading, and merging with CLI and kernel cmdline.
- [src/device/discovery.rs](src/device/discovery.rs)
+- [src/device/discovery.rs](../src/device/discovery.rs)
  - Device discovery under /dev with filters and allowlist; probe emptiness safely.
- [src/partition/plan.rs](src/partition/plan.rs)
+- [src/partition/plan.rs](../src/partition/plan.rs)
  - GPT-only planning and application; 1 MiB alignment; create bios boot, ESP, data and cache partitions with strict safety checks.
- [src/fs/plan.rs](src/fs/plan.rs)
+- [src/fs/plan.rs](../src/fs/plan.rs)
  - Filesystem provisioning: vfat for ESP, btrfs for ZOSDATA, bcachefs for SSD+HDD mode; all data filesystems labeled ZOSDATA.
- [src/mount/ops.rs](src/mount/ops.rs)
-  - Mount per-UUID under /var/cache/<UUID>. Optional fstab writing, disabled by default.
- [src/report/state.rs](src/report/state.rs)
+- [src/mount/ops.rs](../src/mount/ops.rs)
+  - Mount scheme:
+    - Root-mount all data filesystems under `/var/mounts/{UUID}` (runtime only)
+      - btrfs root: `rw,noatime,subvolid=5`
+      - bcachefs root: `rw,noatime`
+    - Create or ensure subvolumes on the primary data filesystem: `system`, `etc`, `modules`, `vm-meta`
+    - Mount final subvolume/subdir targets at `/var/cache/{system,etc,modules,vm-meta}`
+    - Optional fstab writing: only the four final targets, deterministic order, `UUID=` sources; disabled by default
+- [src/report/state.rs](../src/report/state.rs)
  - Build and write JSON state report with version field.
- [src/orchestrator/run.rs](src/orchestrator/run.rs)
+- [src/orchestrator/run.rs](../src/orchestrator/run.rs)
  - One-shot flow orchestration with abort-on-any-validation-error policy.
- [src/idempotency/mod.rs](src/idempotency/mod.rs)
+- [src/idempotency/mod.rs](../src/idempotency/mod.rs)
  - Detect prior provisioning via GPT names and labels; return success-without-changes.
- [src/util/mod.rs](src/util/mod.rs)
+- [src/util/mod.rs](../src/util/mod.rs)
  - Shell-out, udev settle, and helpers.

 Public API surface (signatures; implementation to follow after approval)
 Entrypoint and orchestrator
- [fn main()](src/main.rs:1)
- [struct Context](src/orchestrator/run.rs:1)
- [fn run(ctx: &Context) -> Result<()>](src/orchestrator/run.rs:1)
+- [fn main()](../src/main.rs:1)
+- [struct Context](../src/orchestrator/run.rs:1)
+- [fn run(ctx: &Context) -> Result<()>](../src/orchestrator/run.rs:1)

 CLI
- [struct Cli](src/cli/args.rs:1)
- [fn from_args() -> Cli](src/cli/args.rs:1)
+- [struct Cli](../src/cli/args.rs:1)
+- [fn from_args() -> Cli](../src/cli/args.rs:1)

 Logging
- [struct LogOptions](src/logging/mod.rs:1)
- [fn init_logging(opts: &LogOptions) -> Result<()>](src/logging/mod.rs:1)
+- [struct LogOptions](../src/logging/mod.rs:1)
+- [fn init_logging(opts: &LogOptions) -> Result<()>](../src/logging/mod.rs:1)

 Config
- [struct Config](src/types.rs:1)
- [enum Topology](src/types.rs:1)
- [struct DeviceSelection](src/types.rs:1)
- [struct FsOptions](src/types.rs:1)
- [struct MountScheme](src/types.rs:1)
- [fn load_and_merge(cli: &Cli) -> Result<Config>](src/config/loader.rs:1)
- [fn validate(cfg: &Config) -> Result<()>](src/config/loader.rs:1)
+- [struct Config](../src/types.rs:1)
+- [enum Topology](../src/types.rs:1)
+- [struct DeviceSelection](../src/types.rs:1)
+- [struct FsOptions](../src/types.rs:1)
+- [struct MountScheme](../src/types.rs:1)
+- [fn load_and_merge(cli: &Cli) -> Result<Config>](../src/config/loader.rs:1)
+- [fn validate(cfg: &Config) -> Result<()>](../src/config/loader.rs:1)

 Device discovery
- [struct Disk](src/device/discovery.rs:1)
- [struct DeviceFilter](src/device/discovery.rs:1)
- [trait DeviceProvider](src/device/discovery.rs:1)
- [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](src/device/discovery.rs:1)
+- [struct Disk](../src/device/discovery.rs:1)
+- [struct DeviceFilter](../src/device/discovery.rs:1)
+- [trait DeviceProvider](../src/device/discovery.rs:1)
+- [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](../src/device/discovery.rs:1)

 Partitioning
- [struct PartitionSpec](src/partition/plan.rs:1)
- [struct PartitionPlan](src/partition/plan.rs:1)
- [struct PartitionResult](src/partition/plan.rs:1)
- [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](src/partition/plan.rs:1)
- [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](src/partition/plan.rs:1)
+- [struct PartitionSpec](../src/partition/plan.rs:1)
+- [struct PartitionPlan](../src/partition/plan.rs:1)
+- [struct PartitionResult](../src/partition/plan.rs:1)
+- [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](../src/partition/plan.rs:1)
+- [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](../src/partition/plan.rs:1)

 Filesystems
- [enum FsKind](src/fs/plan.rs:1)
- [struct FsSpec](src/fs/plan.rs:1)
- [struct FsPlan](src/fs/plan.rs:1)
- [struct FsResult](src/fs/plan.rs:1)
- [fn plan_filesystems(disks: &[Disk], parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan>](src/fs/plan.rs:1)
- [fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>>](src/fs/plan.rs:1)
+- [enum FsKind](../src/fs/plan.rs:1)
+- [struct FsSpec](../src/fs/plan.rs:1)
+- [struct FsPlan](../src/fs/plan.rs:1)
+- [struct FsResult](../src/fs/plan.rs:1)
+- [fn plan_filesystems(disks: &[Disk], parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan>](../src/fs/plan.rs:1)
+- [fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>>](../src/fs/plan.rs:1)

 Mounting
- [struct MountPlan](src/mount/ops.rs:1)
- [struct MountResult](src/mount/ops.rs:1)
- [fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan>](src/mount/ops.rs:1)
- [fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>>](src/mount/ops.rs:1)
- [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()>](src/mount/ops.rs:1)
+- [struct MountPlan](../src/mount/ops.rs:1)
+- [struct MountResult](../src/mount/ops.rs:1)
+- [fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan>](../src/mount/ops.rs:1)
+- [fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>>](../src/mount/ops.rs:1)
+- [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()>](../src/mount/ops.rs:1)

 Reporting
- [const REPORT_VERSION: &str](src/report/state.rs:1)
- [struct StateReport](src/report/state.rs:1)
- [fn build_report(...) -> StateReport](src/report/state.rs:1)
- [fn write_report(report: &StateReport) -> Result<()>](src/report/state.rs:1)
+- [const REPORT_VERSION: &str](../src/report/state.rs:1)
+- [struct StateReport](../src/report/state.rs:1)
+- [fn build_report(...) -> StateReport](../src/report/state.rs:1)
+- [fn write_report(report: &StateReport) -> Result<()>](../src/report/state.rs:1)

 Idempotency
- [fn detect_existing_state() -> Result<Option<StateReport>>](src/idempotency/mod.rs:1)
- [fn is_empty_disk(disk: &Disk) -> Result<bool>](src/idempotency/mod.rs:1)
+- [fn detect_existing_state() -> Result<Option<StateReport>>](../src/idempotency/mod.rs:1)
+- [fn is_empty_disk(disk: &Disk) -> Result<bool>](../src/idempotency/mod.rs:1)

 Errors and Result
- [enum Error](src/errors.rs:1)
- [type Result<T> = std::result::Result<T, Error>](src/errors.rs:1)
+- [enum Error](../src/errors.rs:1)
+- [type Result<T> = std::result::Result<T, Error>](../src/errors.rs:1)

 Execution flow

@@ -190,8 +196,15 @@ Filesystem provisioning defaults
 - Filesystem tuning options configurable with sensible defaults and extension points

 Mount scheme and fstab policy
- Mount under /var/cache/<UUID> using filesystem UUID to create stable subdirectories
- Optional /etc/fstab generation disabled by default; when enabled, produce deterministic order with documentation
+- Runtime root mounts:
+  - Each data filesystem is root-mounted at `/var/mounts/{UUID}` (runtime only)
+  - btrfs: `rw,noatime,subvolid=5`; bcachefs: `rw,noatime`
+- Final targets (from primary data filesystem only):
+  - `/var/cache/system`, `/var/cache/etc`, `/var/cache/modules`, `/var/cache/vm-meta`
+  - btrfs subvolume option: `-o subvol={name},noatime`
+  - bcachefs subdir option: `-o X-mount.subdir={name},noatime`
+- /etc/fstab generation:
+  - Disabled by default. When enabled, write only the four final targets with `UUID=` sources in deterministic order. Root mounts under `/var/mounts` are excluded.

 Idempotency detection
 - Consider the system provisioned when expected GPT names and filesystem labels are present and consistent
--- a/docs/Callgraph.svg
+++ b/docs/Callgraph.svg
--- a/docs/DEV_WORKFLOW.md
+++ b/docs/DEV_WORKFLOW.md
@@ -8,18 +8,18 @@ Goal
 Core Principles
 1) Contract-first per module
   - API signatures and responsibilities are documented in [docs/API-SKELETONS.md](docs/API-SKELETONS.md) and mirrored by crate modules:
-     - [src/types.rs](src/types.rs)
-     - [fn load_and_merge()](src/config/loader.rs:1), [fn validate()](src/config/loader.rs:1)
-     - [fn from_args()](src/cli/args.rs:1)
-     - [struct LogOptions](src/logging/mod.rs:1), [fn init_logging()](src/logging/mod.rs:1)
-     - [fn discover()](src/device/discovery.rs:1)
-     - [fn plan_partitions()](src/partition/plan.rs:1), [fn apply_partitions()](src/partition/plan.rs:1)
-     - [fn plan_filesystems()](src/fs/plan.rs:1), [fn make_filesystems()](src/fs/plan.rs:1)
-     - [fn plan_mounts()](src/mount/ops.rs:1), [fn apply_mounts()](src/mount/ops.rs:1), [fn maybe_write_fstab()](src/mount/ops.rs:1)
-     - [const REPORT_VERSION](src/report/state.rs:1), [fn build_report()](src/report/state.rs:1), [fn write_report()](src/report/state.rs:1)
-     - [struct Context](src/orchestrator/run.rs:1), [fn run()](src/orchestrator/run.rs:1)
-     - [fn detect_existing_state()](src/idempotency/mod.rs:1), [fn is_empty_disk()](src/idempotency/mod.rs:1)
-     - [struct CmdOutput](src/util/mod.rs:1), [fn which_tool()](src/util/mod.rs:1), [fn run_cmd()](src/util/mod.rs:1), [fn run_cmd_capture()](src/util/mod.rs:1), [fn udev_settle()](src/util/mod.rs:1)
+     - [src/types.rs](../src/types.rs)
+     - [fn load_and_merge()](../src/config/loader.rs:1), [fn validate()](../src/config/loader.rs:1)
+     - [fn from_args()](../src/cli/args.rs:1)
+     - [struct LogOptions](../src/logging/mod.rs:1), [fn init_logging()](../src/logging/mod.rs:1)
+     - [fn discover()](../src/device/discovery.rs:1)
+     - [fn plan_partitions()](../src/partition/plan.rs:1), [fn apply_partitions()](../src/partition/plan.rs:1)
+     - [fn plan_filesystems()](../src/fs/plan.rs:1), [fn make_filesystems()](../src/fs/plan.rs:1)
+     - [fn plan_mounts()](../src/mount/ops.rs:1), [fn apply_mounts()](../src/mount/ops.rs:1), [fn maybe_write_fstab()](../src/mount/ops.rs:1)
+     - [const REPORT_VERSION](../src/report/state.rs:1), [fn build_report()](../src/report/state.rs:1), [fn write_report()](../src/report/state.rs:1)
+     - [struct Context](../src/orchestrator/run.rs:1), [fn run()](../src/orchestrator/run.rs:1)
+     - [fn detect_existing_state()](../src/idempotency/mod.rs:1), [fn is_empty_disk()](../src/idempotency/mod.rs:1)
+     - [struct CmdOutput](../src/util/mod.rs:1), [fn which_tool()](../src/util/mod.rs:1), [fn run_cmd()](../src/util/mod.rs:1), [fn run_cmd_capture()](../src/util/mod.rs:1), [fn udev_settle()](../src/util/mod.rs:1)

 2) Grep-able region markers in code
   - Every module contains the following optional annotated regions:
@@ -55,22 +55,22 @@ Core Principles
 6) Module ownership and boundaries
   - Add a “Module Responsibilities” section in each module’s header doc comment summarizing scope and non-goals.
   - Example references:
-     - [src/device/discovery.rs](src/device/discovery.rs)
-     - [src/partition/plan.rs](src/partition/plan.rs)
-     - [src/fs/plan.rs](src/fs/plan.rs)
-     - [src/mount/ops.rs](src/mount/ops.rs)
-     - [src/report/state.rs](src/report/state.rs)
+     - [src/device/discovery.rs](../src/device/discovery.rs)
+     - [src/partition/plan.rs](../src/partition/plan.rs)
+     - [src/fs/plan.rs](../src/fs/plan.rs)
+     - [src/mount/ops.rs](../src/mount/ops.rs)
+     - [src/report/state.rs](../src/report/state.rs)

 7) Invariants and safety notes
   - For code that must uphold safety or idempotency invariants, annotate with:
     // SAFETY: explanation
     // IDEMPOTENCY: explanation
   - Example locations:
-     - [fn apply_partitions()](src/partition/plan.rs:1) must enforce empty-disks rule when configured.
-     - [fn make_filesystems()](src/fs/plan.rs:1) must not run if partitioning failed.
+     - [fn apply_partitions()](../src/partition/plan.rs:1) must enforce empty-disks rule when configured.
+     - [fn make_filesystems()](../src/fs/plan.rs:1) must not run if partitioning failed.

 8) Error mapping consistency
-   - Centralize conversions to [enum Error](src/errors.rs:1). When calling external tools, wrap failures into Error::Tool with stderr captured.
+   - Centralize conversions to [enum Error](../src/errors.rs:1). When calling external tools, wrap failures into Error::Tool with stderr captured.
   - Annotate mapping areas with:
     // ERROR: mapping external failure to Error::Tool

@@ -111,7 +111,7 @@ Checklist for adding a new feature
 - Add examples if config or output formats change
  - Update [config/zosstorage.example.yaml](config/zosstorage.example.yaml) or add a new example file
 - Keep error mapping and logging consistent:
-  - Ensure any external tool calls map errors to [enum Error](src/errors.rs:1)
+  - Ensure any external tool calls map errors to [enum Error](../src/errors.rs:1)
 - Run cargo build and update any broken references

 Optional automation (future)
--- a/docs/FUNCTION_LIST.md
+++ b/docs/FUNCTION_LIST.md
@@ -0,0 +1,294 @@
+# Function Reference - Call Graph Analysis
+
+> This documentation is automatically derived from [`Callgraph.svg`](Callgraph.svg) and provides a comprehensive overview of all functions in the zosstorage project, organized by module.
+
+## Table of Contents
+
+- [Main Entry Points](#main-entry-points)
+- [CLI & Configuration](#cli--configuration)
+- [Orchestration](#orchestration)
+- [Device Discovery](#device-discovery)
+- [Partition Management](#partition-management)
+- [Filesystem Operations](#filesystem-operations)
+- [Mount Operations](#mount-operations)
+- [Idempotency & State](#idempotency--state)
+- [Reporting](#reporting)
+- [Utilities](#utilities)
+- [Logging](#logging)
+- [Type Definitions](#type-definitions)
+
+---
+
+## Main Entry Points
+
+### [`src/main.rs`](../src/main.rs)
+
+| Function | Purpose |
+|----------|---------|
+| `main()` | Application entry point; initializes the program and handles top-level errors |
+| `real_main()` | Core application logic; orchestrates the main workflow after initialization |
+
+---
+
+## CLI & Configuration
+
+### [`src/cli/args.rs`](../src/cli/args.rs)
+
+**Structs:** `Cli`, `LogLevelArg` (enum)
+
+| Function | Purpose |
+|----------|---------|
+| `from_args()` | Parses command-line arguments and returns a `Cli` configuration object |
+
+### [`src/config/loader.rs`](../src/config/loader.rs)
+
+| Function | Purpose |
+|----------|---------|
+| `load_and_merge()` | Loads configuration from multiple sources and merges them into a unified config |
+| `validate()` | Validates the merged configuration for correctness and completeness |
+| `to_value()` | Converts configuration structures to internal value representation |
+| `merge_value()` | Recursively merges configuration values, handling conflicts appropriately |
+| `cli_overlay_value()` | Overlays CLI-provided values onto existing configuration |
+| `kernel_cmdline_topology()` | Extracts topology information from kernel command line parameters |
+| `parse_topology_token()` | Parses individual topology tokens from kernel cmdline |
+| `default_config()` | Generates default configuration values when no config file is present |
+
+---
+
+## Orchestration
+
+### [`src/orchestrator/run.rs`](../src/orchestrator/run.rs)
+
+**Structs:** `Context`
+
+| Function | Purpose |
+|----------|---------|
+| `Context::new()` | Creates a new orchestration context with default settings |
+| `Context::with_show()` | Builder method to enable show/dry-run mode |
+| `Context::with_apply()` | Builder method to enable apply mode (actual execution) |
+| `Context::with_report_path()` | Builder method to set the report output path |
+| `Context::with_mount_existing()` | Builder method to configure mounting of existing filesystems |
+| `Context::with_report_current()` | Builder method to enable reporting of current system state |
+| `Context::with_topology_from_cli()` | Builder method to set topology from CLI arguments |
+| `Context::with_topology_from_cmdline()` | Builder method to set topology from kernel cmdline |
+| `run()` | Main orchestration function; coordinates all storage operations |
+| `build_device_filter()` | Constructs device filter based on configuration and user input |
+| `enforce_empty_disks()` | Validates that target disks are empty before proceeding |
+| `role_str()` | Converts partition role enum to human-readable string |
+| `build_summary_json()` | Builds a JSON summary of operations performed |
+
+---
+
+## Device Discovery
+
+### [`src/device/discovery.rs`](../src/device/discovery.rs)
+
+**Structs:** `Disk`, `DeviceFilter`, `SysProvider`  
+**Traits:** `DeviceProvider`
+
+| Function | Purpose |
+|----------|---------|
+| `DeviceFilter::matches()` | Checks if a device matches the configured filter criteria |
+| `SysProvider::new()` | Creates a new sysfs-based device provider |
+| `SysProvider::list_block_devices()` | Lists all block devices found via sysfs |
+| `SysProvider::probe_properties()` | Probes detailed properties of a specific device |
+| `discover()` | Entry point for device discovery using default provider |
+| `discover_with_provider()` | Device discovery with custom provider (for testing/flexibility) |
+| `is_ignored_name()` | Checks if device name should be ignored (loop, ram, etc.) |
+| `sys_block_path()` | Constructs sysfs path for a given block device |
+| `base_name()` | Extracts base device name from path |
+| `is_removable_sysfs()` | Checks if device is removable via sysfs |
+| `is_partition_sysfs()` | Checks if device is a partition via sysfs |
+| `read_disk_size_bytes()` | Reads disk size in bytes from sysfs |
+| `read_rotational()` | Determines if disk is rotational (HDD) or not (SSD) |
+| `read_model_serial()` | Reads device model and serial number |
+| `read_optional_string()` | Utility to safely read optional string values from sysfs |
+
+---
+
+## Partition Management
+
+### [`src/partition/plan.rs`](../src/partition/plan.rs)
+
+**Structs:** `PartitionSpec`, `DiskPlan`, `PartitionPlan`, `PartitionResult`  
+**Enums:** `PartRole`
+
+| Function | Purpose |
+|----------|---------|
+| `plan_partitions()` | Creates partition plans for all target disks based on topology |
+| `apply_partitions()` | Executes partition plans using sgdisk tool |
+| `type_code()` | Returns GPT partition type code for a given partition role |
+| `part_dev_path()` | Constructs device path for a partition (e.g., /dev/sda1) |
+| `sector_size_bytes()` | Reads logical sector size of disk |
+| `parse_sgdisk_info()` | Parses output from sgdisk to extract partition information |
+
+---
+
+## Filesystem Operations
+
+### [`src/fs/plan.rs`](../src/fs/plan.rs)
+
+**Structs:** `FsSpec`, `FsPlan`, `FsResult`  
+**Enums:** `FsKind`
+
+| Function | Purpose |
+|----------|---------|
+| `plan_filesystems()` | Plans filesystem creation for all partitions |
+| `make_filesystems()` | Creates filesystems according to plan (mkfs.* tools) |
+| `capture_uuid()` | Captures UUID of newly created filesystem |
+| `parse_blkid_export()` | Parses blkid export format to extract filesystem metadata |
+| `probe_existing_filesystems()` | Detects existing filesystems on partitions |
+
+---
+
+## Mount Operations
+
+### [`src/mount/ops.rs`](../src/mount/ops.rs)
+
+**Structs:** `PlannedMount`, `PlannedSubvolMount`, `MountPlan`, `MountResult`
+
+| Function | Purpose |
+|----------|---------|
+| `fstype_str()` | Converts FsKind enum to mount filesystem type string |
+| `plan_mounts()` | Creates mount plans for all filesystems |
+| `apply_mounts()` | Executes mount operations and creates mount points |
+| `maybe_write_fstab()` | Conditionally writes /etc/fstab entries for persistent mounts |
+
+---
+
+## Idempotency & State
+
+### [`src/idempotency/mod.rs`](../src/idempotency/mod.rs)
+
+| Function | Purpose |
+|----------|---------|
+| `detect_existing_state()` | Detects existing partitions and filesystems to avoid destructive operations |
+| `is_empty_disk()` | Checks if a disk has no partition table or filesystems |
+| `parse_blkid_export()` | Parses blkid output to identify existing filesystems |
+| `read_proc_partitions_names()` | Reads partition names from /proc/partitions |
+| `base_name()` | Extracts base name from device path |
+| `is_partition_of()` | Checks if one device is a partition of another |
+
+---
+
+## Reporting
+
+### [`src/report/state.rs`](../src/report/state.rs)
+
+**Structs:** `StateReport`
+
+| Function | Purpose |
+|----------|---------|
+| `build_report()` | Builds comprehensive state report of operations performed |
+| `write_report()` | Writes report to specified output path (JSON format) |
+
+---
+
+## Utilities
+
+### [`src/util/mod.rs`](../src/util/mod.rs)
+
+**Structs:** `CmdOutput`
+
+| Function | Purpose |
+|----------|---------|
+| `which_tool()` | Locates external tool in PATH (sgdisk, mkfs.*, etc.) |
+| `run_cmd()` | Executes shell command and returns exit status |
+| `run_cmd_capture()` | Executes command and captures stdout/stderr |
+| `udev_settle()` | Waits for udev to process device events |
+| `is_efi_boot()` | Detects if system booted in EFI mode |
+
+---
+
+## Logging
+
+### [`src/logging/mod.rs`](../src/logging/mod.rs)
+
+**Structs:** `LogOptions`
+
+| Function | Purpose |
+|----------|---------|
+| `LogOptions::from_cli()` | Creates logging configuration from CLI arguments |
+| `level_from_str()` | Converts string to log level enum |
+| `init_logging()` | Initializes logging subsystem with configured options |
+
+---
+
+## Type Definitions
+
+### [`src/types.rs`](../src/types.rs)
+
+**Core Configuration Structures:**
+
+- `Config` - Top-level configuration structure
+- `LoggingConfig` - Logging configuration
+- `DeviceSelection` - Device selection criteria
+- `Topology` - Storage topology definition (enum)
+- `Partitioning` - Partition layout specification
+- `BiosBootSpec`, `EspSpec`, `DataSpec`, `CacheSpec` - Partition type specifications
+- `FsOptions`, `BtrfsOptions`, `BcachefsOptions`, `VfatOptions` - Filesystem options
+- `MountScheme`, `MountSchemeKind` - Mount configuration
+- `ReportOptions` - Report generation configuration
+
+### [`src/errors.rs`](../src/errors.rs)
+
+**Error Types:**
+
+- `Error` - Main error enum for all error conditions
+- `Result<T>` - Type alias for `std::result::Result<T, Error>`
+
+---
+
+## Call Graph Relationships
+
+### Main Execution Flow
+
+```
+main() → real_main() → orchestrator::run()
+    ↓
+    ├─→ cli::from_args()
+    ├─→ config::load_and_merge()
+    ├─→ logging::init_logging()
+    ├─→ device::discover()
+    ├─→ partition::plan_partitions()
+    ├─→ partition::apply_partitions()
+    ├─→ fs::plan_filesystems()
+    ├─→ fs::make_filesystems()
+    ├─→ mount::plan_mounts()
+    ├─→ mount::apply_mounts()
+    └─→ report::build_report() / write_report()
+```
+
+### Key Dependencies
+
+- **Orchestrator** (`run()`) calls: All major subsystems
+- **Device Discovery** uses: Utilities for system probing
+- **Partition/FS/Mount** operations use: Utilities for command execution
+- **All operations** call: `util::run_cmd()` or `util::run_cmd_capture()`
+- **Idempotency checks** called by: Orchestrator before destructive operations
+
+---
+
+## Function Count Summary
+
+- **Main Entry**: 2 functions
+- **CLI & Config**: 9 functions
+- **Orchestration**: 13 functions  
+- **Device Discovery**: 14 functions
+- **Partition Management**: 6 functions
+- **Filesystem Operations**: 5 functions
+- **Mount Operations**: 4 functions
+- **Idempotency**: 6 functions
+- **Reporting**: 2 functions
+- **Utilities**: 6 functions
+- **Logging**: 3 functions
+
+**Total: 70 documented functions** across 15 source files
+
+---
+
+## References
+
+- Original call graph visualization: [`docs/Callgraph.svg`](Callgraph.svg)
+- Architecture documentation: [`docs/ARCHITECTURE.md`](ARCHITECTURE.md)
+- API documentation: [`docs/API.md`](API.md)
--- a/docs/SCHEMA.md
+++ b/docs/SCHEMA.md
@@ -1,27 +1,16 @@
-# zosstorage Configuration Schema
+# zosstorage Configuration (Deprecated schema)

-This document defines the YAML configuration for the initramfs-only disk provisioning utility and the exact precedence rules between configuration sources. It complements [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md).
+This schema document is deprecated per [docs/adr/0002-defaults-only-no-external-config.md](docs/adr/0002-defaults-only-no-external-config.md). Runtime now uses defaults-only with a single optional kernel cmdline override. The YAML configuration file is not read at boot.

-Canonical paths and keys
- Kernel cmdline key: zosstorage.config=
- Default config file path: /etc/zosstorage/config.yaml
- JSON state report path: /run/zosstorage/state.json
- Optional log file path: /run/zosstorage/zosstorage.log
- fstab generation: disabled by default
- Reserved filesystem labels: ZOSBOOT (ESP), ZOSDATA (all data filesystems)
- GPT partition names: zosboot, zosdata, zoscache
+Active behavior (ADR-0002)
+- Defaults-only: all settings are defined in code. No /etc/zosstorage/config.yaml is read.
+- Optional kernel cmdline override: `zosstorage.topology=VALUE` can override only the topology. Legacy alias `zosstorage.topo=` is accepted.
+- CLI: `--config` and `--topology` are deprecated and ignored (warnings emitted). Operational flags remain (`--apply`, `--show`, `--report`, `--fstab`, logging).
+- Report path: `/run/zosstorage/state.json`. Optional log file: `/run/zosstorage/zosstorage.log`.
+- Reserved labels: `ZOSBOOT` (ESP), `ZOSDATA` (data). GPT names: `zosboot`, `zosdata`, `zoscache`.

-Precedence and merge strategy
-1. Start from built-in defaults documented here.
-2. Merge in the on-disk config file if present at /etc/zosstorage/config.yaml.
-3. Merge CLI flags next; these override file values.
-4. Merge kernel cmdline last; zosstorage.config= overrides CLI and file.
-5. No interactive prompts are permitted.
-
-The kernel cmdline key zosstorage.config= accepts:
- A path to a YAML file inside the initramfs root (preferred).
- A file: absolute path (e.g., file:/run/config/zos.yaml).
- A data: URL containing base64 YAML (optional extension).
+Historical reference (original YAML-based schema, no longer used at runtime)
+The remainder of this document preserves the previous YAML schema for archival purposes only.

 Top-level YAML structure

@@ -43,7 +32,7 @@ device_selection:
  allow_removable: false     # future option; default false
  min_size_gib: 10           # ignore devices smaller than this (default 10)
 topology:                    # desired overall layout; see values below
-  mode: single               # single | dual_independent | ssd_hdd_bcachefs | btrfs_raid1 (optional)
+  mode: btrfs_single         # btrfs_single | bcachefs_single | dual_independent | bcachefs-2copy | ssd_hdd_bcachefs | btrfs_raid1
 partitioning:
  alignment_mib: 1           # GPT alignment in MiB
  require_empty_disks: true  # abort if any partition or FS signatures exist
@@ -83,8 +72,8 @@ report:
 Topology modes
 - btrfs_single: One eligible disk. Create BIOS boot (if enabled), ESP 512 MiB, remainder as data. Create a btrfs filesystem labeled ZOSDATA on the data partition.
 - bcachefs_single: One eligible disk. Create BIOS boot (if enabled), ESP 512 MiB, remainder as data. Create a bcachefs filesystem labeled ZOSDATA on the data partition.
- dual_independent: Two eligible disks. On each disk, create BIOS boot (if enabled) + ESP + data. Create an independent btrfs filesystem labeled ZOSDATA on each data partition. No RAID by default.
- bcachefs_2copy: Two eligible disks. Create data partitions on both, then create a single multi-device bcachefs labeled ZOSDATA spanning the data partitions (two-copies semantics to be tuned via mkfs options in a follow-up).
+- dual_independent: One or more eligible disks. On each disk, create BIOS boot (if enabled) + ESP + data. Create an independent btrfs filesystem labeled ZOSDATA on each data partition. No RAID by default.
+- bcachefs-2copy: Two or more eligible disks (minimum 2). Create data partitions and then a single multi-device bcachefs labeled ZOSDATA spanning those data partitions. The mkfs step uses `--replicas=2` (data and metadata).
 - ssd_hdd_bcachefs: One SSD/NVMe and one HDD. Create BIOS boot (if enabled) + ESP on both as required. Create cache (on SSD) and data/backing (on HDD) partitions named zoscache and zosdata respectively. Create a bcachefs labeled ZOSDATA across SSD(HDD) per policy (SSD cache/promote; HDD backing).
 - btrfs_raid1: Optional mode if explicitly requested. Create mirrored btrfs across two disks for the data role with raid1 profile. Not enabled by default.

@@ -119,11 +108,15 @@ Filesystem section
 - vfat: label ZOSBOOT used for ESP.

 Mount section
- base_dir: default /var/cache.
- scheme:
-  - per_uuid: mount data filesystems at /var/cache/<FS-UUID>
-  - custom: reserved for future mapping-by-config, not yet implemented.
- fstab.enabled: default false. When true, zosstorage will generate fstab entries in deterministic order.
+- Runtime root mounts (all data filesystems):
+  - Each data filesystem is root-mounted at `/var/mounts/{UUID}`
+  - btrfs root mount options: `rw,noatime,subvolid=5`
+  - bcachefs root mount options: `rw,noatime`
+- Subvolume mounts (from the primary data filesystem only) to final targets:
+  - Targets: `/var/cache/system`, `/var/cache/etc`, `/var/cache/modules`, `/var/cache/vm-meta`
+  - btrfs subvol options: `-o rw,noatime,subvol={name}`
+  - bcachefs subdir options: `-o rw,noatime,X-mount.subdir={name}`
+- fstab.enabled: default false. When true, zosstorage writes only the four subvolume mount entries, in deterministic target order, using `UUID=` sources for the filesystem; root mounts under `/var/mounts` are excluded.

 Report section
 - path: default /run/zosstorage/state.json.
@@ -135,7 +128,7 @@ Minimal single-disk btrfs
 ```yaml
 version: 1
 topology:
-  mode: single
+  mode: btrfs_single
 ```

 Dual independent btrfs (two disks)
@@ -186,15 +179,15 @@ Future extensions
 - Multiple topology groups on multi-disk systems

 Reference modules
- [src/types.rs](src/types.rs)
- [src/config/loader.rs](src/config/loader.rs)
- [src/cli/args.rs](src/cli/args.rs)
- [src/orchestrator/run.rs](src/orchestrator/run.rs)
- [src/partition/plan.rs](src/partition/plan.rs)
- [src/fs/plan.rs](src/fs/plan.rs)
- [src/mount/ops.rs](src/mount/ops.rs)
- [src/report/state.rs](src/report/state.rs)
- [src/idempotency/mod.rs](src/idempotency/mod.rs)
+- [src/types.rs](../src/types.rs)
+- [src/config/loader.rs](../src/config/loader.rs)
+- [src/cli/args.rs](../src/cli/args.rs)
+- [src/orchestrator/run.rs](../src/orchestrator/run.rs)
+- [src/partition/plan.rs](../src/partition/plan.rs)
+- [src/fs/plan.rs](../src/fs/plan.rs)
+- [src/mount/ops.rs](../src/mount/ops.rs)
+- [src/report/state.rs](../src/report/state.rs)
+- [src/idempotency/mod.rs](../src/idempotency/mod.rs)

 Change log
 - v1: Initial draft of schema and precedence rules
--- a/docs/SPECS.md
+++ b/docs/SPECS.md
@@ -3,31 +3,31 @@
 This document finalizes core specifications required before code skeleton implementation. It complements [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md) and [docs/SCHEMA.md](docs/SCHEMA.md), and references the API declarations listed in [docs/API.md](docs/API.md).

 Linked modules and functions
- Logging module: [src/logging/mod.rs](src/logging/mod.rs)
-  - [fn init_logging(opts: &LogOptions) -> Result<()>](src/logging/mod.rs:1)
- Report module: [src/report/state.rs](src/report/state.rs)
-  - [const REPORT_VERSION: &str](src/report/state.rs:1)
-  - [fn build_report(...) -> StateReport](src/report/state.rs:1)
-  - [fn write_report(report: &StateReport) -> Result<()>](src/report/state.rs:1)
- Device module: [src/device/discovery.rs](src/device/discovery.rs)
-  - [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](src/device/discovery.rs:1)
- Partitioning module: [src/partition/plan.rs](src/partition/plan.rs)
-  - [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](src/partition/plan.rs:1)
-  - [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](src/partition/plan.rs:1)
- Filesystems module: [src/fs/plan.rs](src/fs/plan.rs)
-  - [fn plan_filesystems(disks: &[Disk], parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan>](src/fs/plan.rs:1)
-  - [fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>>](src/fs/plan.rs:1)
- Mount module: [src/mount/ops.rs](src/mount/ops.rs)
-  - [fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan>](src/mount/ops.rs:1)
-  - [fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>>](src/mount/ops.rs:1)
-  - [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()>](src/mount/ops.rs:1)
- Idempotency module: [src/idempotency/mod.rs](src/idempotency/mod.rs)
-  - [fn detect_existing_state() -> Result<Option<StateReport>>](src/idempotency/mod.rs:1)
-  - [fn is_empty_disk(disk: &Disk) -> Result<bool>](src/idempotency/mod.rs:1)
- CLI module: [src/cli/args.rs](src/cli/args.rs)
-  - [fn from_args() -> Cli](src/cli/args.rs:1)
- Orchestrator: [src/orchestrator/run.rs](src/orchestrator/run.rs)
-  - [fn run(ctx: &Context) -> Result<()>](src/orchestrator/run.rs:1)
+- Logging module: [src/logging/mod.rs](../src/logging/mod.rs)
+  - [fn init_logging(opts: &LogOptions) -> Result<()>](../src/logging/mod.rs:1)
+- Report module: [src/report/state.rs](../src/report/state.rs)
+  - [const REPORT_VERSION: &str](../src/report/state.rs:1)
+  - [fn build_report(...) -> StateReport](../src/report/state.rs:1)
+  - [fn write_report(report: &StateReport) -> Result<()>](../src/report/state.rs:1)
+- Device module: [src/device/discovery.rs](../src/device/discovery.rs)
+  - [fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>>](../src/device/discovery.rs:1)
+- Partitioning module: [src/partition/plan.rs](../src/partition/plan.rs)
+  - [fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan>](../src/partition/plan.rs:1)
+  - [fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>>](../src/partition/plan.rs:1)
+- Filesystems module: [src/fs/plan.rs](../src/fs/plan.rs)
+  - [fn plan_filesystems(disks: &[Disk], parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan>](../src/fs/plan.rs:1)
+  - [fn make_filesystems(plan: &FsPlan) -> Result<Vec<FsResult>>](../src/fs/plan.rs:1)
+- Mount module: [src/mount/ops.rs](../src/mount/ops.rs)
+  - [fn plan_mounts(fs_results: &[FsResult], cfg: &Config) -> Result<MountPlan>](../src/mount/ops.rs:1)
+  - [fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>>](../src/mount/ops.rs:1)
+  - [fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()>](../src/mount/ops.rs:1)
+- Idempotency module: [src/idempotency/mod.rs](../src/idempotency/mod.rs)
+  - [fn detect_existing_state() -> Result<Option<StateReport>>](../src/idempotency/mod.rs:1)
+  - [fn is_empty_disk(disk: &Disk) -> Result<bool>](../src/idempotency/mod.rs:1)
+- CLI module: [src/cli/args.rs](../src/cli/args.rs)
+  - [fn from_args() -> Cli](../src/cli/args.rs:1)
+- Orchestrator: [src/orchestrator/run.rs](../src/orchestrator/run.rs)
+  - [fn run(ctx: &Context) -> Result<()>](../src/orchestrator/run.rs:1)

 ---

@@ -39,7 +39,7 @@ Goals

 Configuration
 - Levels: error, warn, info, debug (default info).
- Propagation: single global initialization via [fn init_logging](src/logging/mod.rs:1). Subsequent calls must be no-ops.
+- Propagation: single global initialization via [fn init_logging](../src/logging/mod.rs:1). Subsequent calls must be no-ops.

 Implementation notes
 - Use tracing and tracing-subscriber.
@@ -57,7 +57,7 @@ Location
 - Default output: /run/zosstorage/state.json

 Versioning
- Include a top-level string field version equal to [REPORT_VERSION](src/report/state.rs:1). Start with v1.
+- Include a top-level string field version equal to [REPORT_VERSION](../src/report/state.rs:1). Start with v1.

 Schema example

@@ -154,17 +154,17 @@ Default exclude patterns
 - ^/dev/fd\\d+$

 Selection policy
- Compile include and exclude regex into [DeviceFilter](src/device/discovery.rs).
+- Compile include and exclude regex into [DeviceFilter](../src/device/discovery.rs).
 - Enumerate device candidates and apply:
  - Must match at least one include.
  - Must not match any exclude.
  - Must be larger than min_size_gib (default 10).
 - Probing
  - Gather size, rotational flag, model, serial when available.
-  - Expose via [struct Disk](src/device/discovery.rs:1).
+  - Expose via [struct Disk](../src/device/discovery.rs:1).

 No eligible disks
- Return a specific error variant in [enum Error](src/errors.rs:1).
+- Return a specific error variant in [enum Error](../src/errors.rs:1).

 ---

@@ -181,17 +181,20 @@ Layout defaults
 - Cache partitions (only in ssd_hdd_bcachefs): GPT name zoscache on SSD.

 Per-topology specifics
- single: All roles on the single disk.
- dual_independent: Each disk gets BIOS boot + ESP + data.
- ssd_hdd_bcachefs: SSD gets BIOS boot + ESP + zoscache, HDD gets BIOS boot + ESP + zosdata.
+- btrfs_single: All roles on the single disk; data formatted as btrfs.
+- bcachefs_single: All roles on the single disk; data formatted as bcachefs.
+- dual_independent: On each eligible disk (one or more), create BIOS boot (if applicable), ESP, and data.
+- bcachefs-2copy: Create data partitions on two or more disks; later formatted as one multi-device bcachefs spanning all data partitions.
+- ssd_hdd_bcachefs: SSD gets BIOS boot + ESP + zoscache; HDD gets BIOS boot + ESP + zosdata; combined later into one bcachefs.
+- btrfs_raid1: Two disks minimum; data partitions mirrored via btrfs RAID1.

 Safety checks
 - Ensure unique partition UUIDs.
- Verify no pre-existing partitions or signatures. Use blkid or similar via [run_cmd_capture](src/util/mod.rs:1).
- After partition creation, run udev settle via [udev_settle](src/util/mod.rs:1).
+- Verify no pre-existing partitions or signatures. Use blkid or similar via [run_cmd_capture](../src/util/mod.rs:1).
+- After partition creation, run udev settle via [udev_settle](../src/util/mod.rs:1).

 Application
- Utilize sgdisk helpers in [apply_partitions](src/partition/plan.rs:1).
+- Utilize sgdisk helpers in [apply_partitions](../src/partition/plan.rs:1).

 ---

@@ -199,34 +202,38 @@ Application

 Kinds
 - Vfat for ESP, label ZOSBOOT.
- Btrfs for data on single and dual_independent.
- Bcachefs for ssd_hdd_bcachefs (SSD cache, HDD backing).
+- Btrfs for data in btrfs_single, dual_independent, and btrfs_raid1 (with RAID1 profile).
+- Bcachefs for data in bcachefs_single, ssd_hdd_bcachefs (SSD cache + HDD backing), and bcachefs-2copy (multi-device).
 - All data filesystems use label ZOSDATA.

 Defaults
- btrfs: compression zstd:3, raid_profile none unless explicitly set to raid1 in btrfs_raid1 mode.
- bcachefs: cache_mode promote, compression zstd, checksum crc32c.
+- btrfs: compression zstd:3, raid_profile none unless explicitly set; for btrfs_raid1 use -m raid1 -d raid1.
+- bcachefs: cache_mode promote, compression zstd, checksum crc32c; for bcachefs-2copy use `--replicas=2` (data and metadata).
 - vfat: ESP label ZOSBOOT.

 Planning and execution
- Decide mapping of [PartitionResult](src/partition/plan.rs:1) to [FsSpec](src/fs/plan.rs:1) in [plan_filesystems](src/fs/plan.rs:1).
- Create filesystems in [make_filesystems](src/fs/plan.rs:1) through wrapped mkfs tools.
- Capture resulting identifiers (fs uuid, label) in [FsResult](src/fs/plan.rs:1).
+- Decide mapping of [PartitionResult](../src/partition/plan.rs:1) to [FsSpec](../src/fs/plan.rs:1) in [plan_filesystems](../src/fs/plan.rs:1).
+- Create filesystems in [make_filesystems](../src/fs/plan.rs:1) through wrapped mkfs tools.
+- Capture resulting identifiers (fs uuid, label) in [FsResult](../src/fs/plan.rs:1).

 ---

 ## 6. Mount scheme and fstab policy

-Scheme
- per_uuid under /var/cache: directories named as filesystem UUIDs.
+Runtime root mounts (all data filesystems)
+- Each data filesystem is root-mounted at `/var/mounts/{UUID}` (runtime only).
+- btrfs root mount options: `rw,noatime,subvolid=5`
+- bcachefs root mount options: `rw,noatime`

-Mount options
- btrfs: ssd when non-rotational underlying device, compress from config, defaults otherwise.
- vfat: defaults, utf8.
+Final subvolume/subdir mounts (from the primary data filesystem)
+- Create or ensure subvolumes named: `system`, `etc`, `modules`, `vm-meta`
+- Mount targets: `/var/cache/system`, `/var/cache/etc`, `/var/cache/modules`, `/var/cache/vm-meta`
+- btrfs options: `-o rw,noatime,subvol={name}`
+- bcachefs options: `-o rw,noatime,X-mount.subdir={name}`

-fstab
+fstab policy
 - Disabled by default.
- When enabled, [maybe_write_fstab](src/mount/ops.rs:1) writes deterministic entries sorted by target path.
+- When enabled, [maybe_write_fstab](../src/mount/ops.rs:1) writes only the four final subvolume/subdir entries using `UUID=` sources, in deterministic target order. Root mounts under `/var/mounts` are excluded.

 ---

@@ -235,20 +242,23 @@ fstab
 Signals for already-provisioned system
 - Expected GPT names found: zosboot, zosdata, and zoscache when applicable.
 - Filesystems with labels ZOSBOOT for ESP and ZOSDATA for all data filesystems.
- When consistent with selected topology, [detect_existing_state](src/idempotency/mod.rs:1) returns a StateReport and orchestrator exits success without changes.
+- When consistent with selected topology, [detect_existing_state](../src/idempotency/mod.rs:1) returns a StateReport and orchestrator exits success without changes.

 Disk emptiness
- [is_empty_disk](src/idempotency/mod.rs:1) checks for absence of partitions and FS signatures before any modification.
+- [is_empty_disk](../src/idempotency/mod.rs:1) checks for absence of partitions and FS signatures before any modification.

 ---

 ## 8. CLI flags and help text outline

-Flags mirrored by [struct Cli](src/cli/args.rs:1) parsed via [from_args](src/cli/args.rs:1)
+Flags mirrored by [struct Cli](../src/cli/args.rs:1) parsed via [from_args](../src/cli/args.rs:1)
 - --config PATH
 - --log-level LEVEL    error | warn | info | debug
 - --log-to-file
 - --fstab              enable fstab generation
+- --show               print preview JSON to stdout (non-destructive)
+- --report PATH        write preview JSON to file (non-destructive)
+- --apply              perform partitioning, filesystem creation, and mounts (DESTRUCTIVE)
 - --force              present but returns unimplemented error

 Kernel cmdline
@@ -257,7 +267,7 @@ Kernel cmdline
 Help text sections
 - NAME, SYNOPSIS, DESCRIPTION
 - CONFIG PRECEDENCE
- TOPOLOGIES: single, dual_independent, ssd_hdd_bcachefs, btrfs_raid1
+- TOPOLOGIES: btrfs_single, bcachefs_single, dual_independent, bcachefs-2copy, ssd_hdd_bcachefs, btrfs_raid1
 - SAFETY AND IDEMPOTENCY
 - REPORTS
 - EXIT CODES: 0 success or already_provisioned, non-zero on error
@@ -267,9 +277,10 @@ Help text sections
 ## 9. Integration testing plan (QEMU KVM)

 Scenarios to scaffold in [tests/](tests/)
- Single disk 40 GiB virtio: validates single topology end-to-end smoke.
- Dual NVMe 40 GiB each: validates dual_independent topology.
- SSD NVMe + HDD virtio: validates ssd_hdd_bcachefs topology.
+- Single disk 40 GiB virtio: validates btrfs_single topology end-to-end smoke.
+- Dual NVMe 40 GiB each: validates dual_independent topology (independent btrfs per disk).
+- SSD NVMe + HDD virtio: validates ssd_hdd_bcachefs topology (bcachefs with SSD cache/promote, HDD backing).
+- Three disks: validates bcachefs-2copy across data partitions using `--replicas=2`.
 - Negative: no eligible disks, or non-empty disk should abort.

 Test strategy
@@ -281,7 +292,7 @@ Test strategy
 Artifacts to validate
 - Presence of expected partition GPT names.
 - Filesystems created with correct labels.
- Mountpoints under /var/cache/<UUID> when running in a VM.
+- Runtime root mounts under `/var/mounts/{UUID}` and final subvolume targets at `/var/cache/{system,etc,modules,vm-meta}`.
 - JSON report validates against v1 schema.

 ---
--- a/docs/adr/0001-modular-workflow.md
+++ b/docs/adr/0001-modular-workflow.md
@@ -47,14 +47,14 @@ Consequences

 Implementation Notes
 - Region markers have been added to key modules:
-  - [src/config/loader.rs](src/config/loader.rs)
-  - [src/orchestrator/run.rs](src/orchestrator/run.rs)
-  - [src/cli/args.rs](src/cli/args.rs)
-  - [src/device/discovery.rs](src/device/discovery.rs)
-  - [src/partition/plan.rs](src/partition/plan.rs)
-  - [src/fs/plan.rs](src/fs/plan.rs)
-  - [src/mount/ops.rs](src/mount/ops.rs)
-  - [src/report/state.rs](src/report/state.rs)
+  - [src/config/loader.rs](../src/config/loader.rs)
+  - [src/orchestrator/run.rs](../src/orchestrator/run.rs)
+  - [src/cli/args.rs](../src/cli/args.rs)
+  - [src/device/discovery.rs](../src/device/discovery.rs)
+  - [src/partition/plan.rs](../src/partition/plan.rs)
+  - [src/fs/plan.rs](../src/fs/plan.rs)
+  - [src/mount/ops.rs](../src/mount/ops.rs)
+  - [src/report/state.rs](../src/report/state.rs)
 - Remaining modules will follow the same pattern as needed (e.g., util, idempotency, main/lib if helpful).

 Related Documents
--- a/docs/adr/0002-defaults-only-no-external-config.md
+++ b/docs/adr/0002-defaults-only-no-external-config.md
@@ -0,0 +1,109 @@
+# ADR 0002: Defaults-Only Configuration; Remove External YAML Config
+
+Status
+- Accepted
+- Date: 2025-10-06
+
+Context
+- Running from initramfs at first boot provides no reliable access to an on-disk configuration file (e.g., /etc/zosstorage/config.yaml). An external file cannot be assumed to exist or be mounted.
+- The previous design added precedence and merge complexity across file, CLI, and kernel cmdline as documented in [docs/SCHEMA.md](../SCHEMA.md) and implemented via [fn load_and_merge()](../../src/config/loader.rs:1), increasing maintenance burden and risks of drift.
+- YAML introduces misconfiguration risk in early boot, adds I/O, and complicates idempotency guarantees without meaningful benefits for the intended minimal-first initializer.
+- The desired model is to ship with sane built-in defaults, selected automatically from detected hardware topology; optional kernel cmdline may override only the topology choice for VM/lab scenarios.
+
+Decision
+- Remove all dependency on an on-disk configuration file:
+  - Do not read /etc/zosstorage/config.yaml or any file-based config.
+  - Deprecate and ignore repository-local config files for runtime (e.g., config/zosstorage.yaml). The example file [config/zosstorage.example.yaml](../../config/zosstorage.example.yaml) remains as historical reference only and may be removed later.
+- Deprecate the --config CLI flag in [struct Cli](../../src/cli/args.rs:1). If present, emit a deprecation warning and ignore it.
+- Retain operational CLI flags and logging controls for usability:
+  - --apply, --show, --report PATH, --fstab, --log-level LEVEL, --log-to-file
+- Replace the prior file/CLI/kernel precedence with a defaults-only policy plus a single optional kernel cmdline override:
+  - Recognized key: zosstorage.topology=VALUE
+  - The key may override only the topology selection; all other settings use built-in defaults.
+- Topology defaults and override policy:
+  - 1 eligible disk:
+    - Default: btrfs_single
+    - Allowed cmdline overrides: btrfs_single, bcachefs_single
+  - 2 eligible disks:
+    - Default: dual_independent
+    - Allowed cmdline overrides: dual_independent, ssd_hdd_bcachefs, btrfs_raid1, bcachefs-2copy
+  - >2 eligible disks:
+    - Default: btrfs_raid1
+    - Allowed cmdline overrides: btrfs_raid1, bcachefs-2copy
+- Accept both snake_case and hyphenated forms for VALUE; canonical for two-copy bcachefs is bcachefs-2copy; normalize to [enum Topology](../../src/types.rs:1):
+  - btrfs_single | btrfs-single
+  - bcachefs_single | bcachefs-single
+  - dual_independent | dual-independent
+  - ssd_hdd_bcachefs | ssd-hdd-bcachefs
+  - btrfs_raid1 | btrfs-raid1
+  - bcachefs-2copy
+- Kernel cmdline parsing beyond topology is deferred; future extensions for VM workflows may be proposed separately.
+
+Rationale
+- Eliminates unreachable configuration paths at first boot and simplifies the mental model.
+- Reduces maintenance overhead by removing schema and precedence logic.
+- Minimizes early-boot I/O and failure modes while preserving a targeted override for lab/VMs.
+- Keeps the tool safe-by-default and fully idempotent without depending on external files.
+
+Consequences
+- Documentation:
+  - Mark [docs/SCHEMA.md](../SCHEMA.md) as deprecated for runtime behavior; retain only as historical reference.
+  - Update [docs/ARCHITECTURE.md](../ARCHITECTURE.md) and [docs/SPECS.md](../SPECS.md) to reflect defaults-only configuration.
+  - Update [docs/API.md](../API.md) and [docs/API-SKELETONS.md](../API-SKELETONS.md) where they reference file-based config.
+- CLI:
+  - [struct Cli](../../src/cli/args.rs:1) keeps operational flags; --config becomes a no-op with a deprecation warning.
+- Code:
+  - Replace [fn load_and_merge()](../../src/config/loader.rs:1) with a minimal loader that:
+    - Builds a [struct Config](../../src/types.rs:1) entirely from baked-in defaults.
+    - Reads /proc/cmdline to optionally parse zosstorage.topology and normalize to [enum Topology](../../src/types.rs:1).
+    - Removes YAML parsing, file reads, and merge logic.
+- Tests:
+  - Remove tests that depend on external YAML; add tests for cmdline override normalization and disk-count defaults.
+
+Defaults (authoritative)
+- Partitioning:
+  - GPT only, 1 MiB alignment, BIOS boot 1 MiB first unless UEFI detected via [fn is_efi_boot()](../../src/util/mod.rs:1).
+  - ESP 512 MiB labeled ZOSBOOT (GPT name: zosboot), data uses GPT name zosdata.
+- Filesystems:
+  - ESP: vfat labeled ZOSBOOT
+  - Data: label ZOSDATA
+  - Backend per topology (btrfs for btrfs_*; bcachefs for ssd_hdd_bcachefs and bcachefs-2copy)
+- Mount scheme:
+  - Root-mount all data filesystems under /var/mounts/{UUID}; final subvolume/subdir mounts from the primary data FS to /var/cache/{system,etc,modules,vm-meta}; fstab remains optional.
+- Idempotency:
+  - Unchanged: already-provisioned signals exit success-without-changes via [fn detect_existing_state()](../../src/idempotency/mod.rs:1).
+
+Implementation Plan
+1) Introduce a minimal defaults loader in [src/config/loader.rs](../../src/config/loader.rs:1):
+   - new internal fn parse_topology_from_cmdline() -> Option<Topology>
+   - new internal fn normalize_topology(s: &str) -> Option<Topology>
+   - refactor load to construct Config from constants + optional topology override
+2) CLI:
+   - Emit deprecation warning when --config is provided; ignore its value.
+3) Docs:
+   - Add deprecation banner to [docs/SCHEMA.md](../SCHEMA.md).
+   - Adjust [README.md](../../README.md) to describe defaults and the zosstorage.topology override.
+4) Tests:
+   - Add unit tests for normalization and disk-count policy; remove YAML-based tests.
+
+Backward Compatibility
+- External YAML configuration is no longer supported at runtime.
+- Kernel cmdline key zosstorage.config= is removed. Only zosstorage.topology remains recognized.
+- The JSON report, labels, GPT names, and mount behavior remain unchanged.
+
+Security and Safety
+- By eliminating external configuration input, we reduce attack surface and misconfiguration risk in early boot.
+- The emptiness and idempotency checks continue to gate destructive operations.
+
+Open Items
+- Decide whether to accept additional synonyms (e.g., “bcachefs-raid1”) and map them to existing [enum Topology](../../src/types.rs:1) variants; default is to reject unknown values with a clear error.
+- Potential future kernel cmdline keys (e.g., logging level) may be explored via a separate ADR.
+
+Links
+- Architecture: [docs/ARCHITECTURE.md](../ARCHITECTURE.md)
+- API Index: [docs/API-SKELETONS.md](../API-SKELETONS.md)
+- Specs: [docs/SPECS.md](../SPECS.md)
+- CLI: [src/cli/args.rs](../../src/cli/args.rs)
+- Config loader: [src/config/loader.rs](../../src/config/loader.rs)
+- Types: [src/types.rs](../../src/types.rs)
+- Util: [src/util/mod.rs](../../src/util/mod.rs)
--- a/docs/callgraph.html
+++ b/docs/callgraph.html
--- a/src/cli/args.rs
+++ b/src/cli/args.rs
@@ -58,8 +58,8 @@ impl std::fmt::Display for LogLevelArg {
 #[derive(Debug, Parser)]
 #[command(name = "zosstorage", disable_help_subcommand = true)]
 pub struct Cli {
-    /// Path to YAML configuration (mirrors kernel cmdline key 'zosstorage.config=')
-    #[arg(short = 'c', long = "config")]
+    /// DEPRECATED: external YAML configuration is not used at runtime (ADR-0002). Ignored with a warning.
+    #[arg(short = 'c', long = "config", hide = true)]
    pub config: Option<String>,

    /// Log level: error, warn, info, debug
@@ -74,7 +74,7 @@ pub struct Cli {
    #[arg(short = 's', long = "fstab", default_value_t = false)]
    pub fstab: bool,

-    /// Select topology (overrides config topology)
+    /// Select topology (CLI has precedence over kernel cmdline)
    #[arg(short = 't', long = "topology", value_enum)]
    pub topology: Option<crate::types::Topology>,

@@ -82,16 +82,24 @@ pub struct Cli {
    #[arg(short = 'f', long = "force")]
    pub force: bool,

-    /// Allow removable devices (e.g., USB sticks) to be considered during discovery
-    /// Overrides config.device_selection.allow_removable when provided
+    /// Include removable devices (e.g., USB sticks) during discovery (default: false)
    #[arg(long = "allow-removable", default_value_t = false)]
    pub allow_removable: bool,

+    /// Attempt to mount existing filesystems based on on-disk headers; no partitioning or mkfs.
+    /// Non-destructive mounting flow; uses UUID= sources and policy from config.
+    #[arg(long = "mount-existing", default_value_t = false)]
+    pub mount_existing: bool,
+
+    /// Report current initialized filesystems and mounts without performing changes.
+    #[arg(long = "report-current", default_value_t = false)]
+    pub report_current: bool,
+
    /// Print detection and planning summary as JSON to stdout (non-default)
    #[arg(long = "show", default_value_t = false)]
    pub show: bool,

-    /// Write detection/planning JSON report to the given path (overrides config.report.path)
+    /// Write detection/planning JSON report to the given path
    #[arg(long = "report")]
    pub report: Option<String>,

--- a/src/config/loader.rs
+++ b/src/config/loader.rs
@@ -1,12 +1,12 @@
 //! Configuration loading, merging, and validation (loader).
 //!
-//! Precedence (highest to lowest):
-//! - Kernel cmdline key `zosstorage.config=`
-//! - CLI flags
-//! - On-disk config file at /etc/zosstorage/config.yaml (if present)
-//! - Built-in defaults
-//!
-//! See [docs/SCHEMA.md](../../docs/SCHEMA.md) for the schema details.
+//// Precedence and policy (ADR-0002):
+//// - Built-in sane defaults for all settings.
+//// - Kernel cmdline key `zosstorage.topology=` (legacy alias `zosstorage.topo=`) may override topology only.
+//// - CLI flags control operational toggles only (logging, fstab, allow-removable).
+//// - `--config` and `--topology` are deprecated and ignored (warnings emitted).
+////
+//// Note: [docs/SCHEMA.md](../../docs/SCHEMA.md) is deprecated for runtime configuration; defaults are code-defined.
 //
 // REGION: API
 // api: config::load_and_merge(cli: &crate::cli::Cli) -> crate::Result<crate::config::types::Config>
@@ -26,7 +26,7 @@
 // REGION: EXTENSION_POINTS-END
 //
 // REGION: SAFETY
-// safety: precedence enforced (kernel > CLI flags > CLI --config > /etc file > defaults).
+// safety: precedence enforced (CLI flags > kernel cmdline > built-in defaults).
 // safety: reserved GPT names and labels validated to avoid destructive operations later.
 // REGION: SAFETY-END
 //
@@ -41,22 +41,21 @@
 // REGION: TODO-END

 use std::fs;
-use std::path::Path;

-use crate::{cli::Cli, Error, Result};
 use crate::types::*;
-use serde_json::{Map, Value};
-use base64::Engine as _;
+use crate::{Error, Result, cli::Cli};
+use serde_json::{Map, Value, json};
+use tracing::warn;

-/// Load defaults, merge on-disk config, overlay CLI, and finally kernel cmdline key.
+//// Build configuration from built-in defaults and minimal operational CLI overlays.
 /// Returns a validated Config on success.
 ///
-/// Behavior:
-/// - Starts from built-in defaults (documented in docs/SCHEMA.md)
-/// - If /etc/zosstorage/config.yaml exists, merge it
-/// - If CLI --config is provided, merge that (overrides file defaults)
-/// - If kernel cmdline provides `zosstorage.config=...`, merge that last (highest precedence)
-/// - Returns Error::Unimplemented when --force is used
+/// Behavior (ADR-0002):
+/// - Start from built-in defaults (code-defined).
+/// - Ignore on-disk YAML and `--config` (deprecated); emit a warning if provided.
+/// - CLI `--topology` is supported and has precedence when provided.
+/// - If CLI does not provide topology, apply kernel cmdline `zosstorage.topology=` (or legacy `zosstorage.topo=`).
+/// - Returns Error::Unimplemented when --force is used.
 pub fn load_and_merge(cli: &Cli) -> Result<Config> {
    if cli.force {
        return Err(Error::Unimplemented("--force flag is not implemented"));
@@ -65,35 +64,23 @@ pub fn load_and_merge(cli: &Cli) -> Result<Config> {
    // 1) Start with defaults
    let mut merged = to_value(default_config())?;

-    // 2) Merge default on-disk config if present
-    let default_cfg_path = "/etc/zosstorage/config.yaml";
-    if Path::new(default_cfg_path).exists() {
-        let v = load_yaml_value(default_cfg_path)?;
-        merge_value(&mut merged, v);
-    }
+    // 2) (initramfs) Skipped reading default on-disk config to avoid dependency on /etc.
+    // If a config is needed, pass it via --config PATH or kernel cmdline `zosstorage.config=...`.

-    // 3) Merge CLI referenced config (if any)
-    if let Some(cfg_path) = &cli.config {
-        let v = load_yaml_value(cfg_path)?;
-        merge_value(&mut merged, v);
+    // 3) Deprecated config file flag: warn and ignore
+    if cli.config.is_some() {
+        warn!("--config is deprecated and ignored (ADR-0002: defaults-only)");
    }
+    // (no file merge)

    // 4) Overlay CLI flags (non-path flags)
    let cli_overlay = cli_overlay_value(cli);
    merge_value(&mut merged, cli_overlay);

-    // 5) Merge kernel cmdline referenced config (if any)
-    if let Some(src) = kernel_cmdline_config_source()? {
-        match src {
-            KernelConfigSource::Path(kpath) => {
-                let v = load_yaml_value(&kpath)?;
-                merge_value(&mut merged, v);
-            }
-            KernelConfigSource::Data(yaml) => {
-                let v: serde_json::Value = serde_yaml::from_str(&yaml)
-                    .map_err(|e| Error::Config(format!("failed to parse YAML from data: URL: {}", e)))?;
-                merge_value(&mut merged, v);
-            }
+    // 5) Kernel cmdline topology override only when CLI did not provide topology
+    if cli.topology.is_none() {
+        if let Some(topo) = kernel_cmdline_topology() {
+            merge_value(&mut merged, json!({"topology": topo.to_string()}));
        }
    }

@@ -141,43 +128,50 @@ pub fn validate(cfg: &Config) -> Result<()> {
    }

    // Reserved GPT names
-    if cfg.partitioning.esp.gpt_name != "zosboot" {
-        return Err(Error::Validation(
-            "partitioning.esp.gpt_name must be 'zosboot'".into(),
-        ));
+    if cfg.partitioning.esp.gpt_name != GPT_NAME_ZOSBOOT {
+        return Err(Error::Validation(format!(
+            "partitioning.esp.gpt_name must be '{}'",
+            GPT_NAME_ZOSBOOT
+        )));
    }
-    if cfg.partitioning.data.gpt_name != "zosdata" {
-        return Err(Error::Validation(
-            "partitioning.data.gpt_name must be 'zosdata'".into(),
-        ));
+    if cfg.partitioning.data.gpt_name != GPT_NAME_ZOSDATA {
+        return Err(Error::Validation(format!(
+            "partitioning.data.gpt_name must be '{}'",
+            GPT_NAME_ZOSDATA
+        )));
    }
-    if cfg.partitioning.cache.gpt_name != "zoscache" {
-        return Err(Error::Validation(
-            "partitioning.cache.gpt_name must be 'zoscache'".into(),
-        ));
+    if cfg.partitioning.cache.gpt_name != GPT_NAME_ZOSCACHE {
+        return Err(Error::Validation(format!(
+            "partitioning.cache.gpt_name must be '{}'",
+            GPT_NAME_ZOSCACHE
+        )));
    }
    // BIOS boot name is also 'zosboot' per current assumption
-    if cfg.partitioning.bios_boot.gpt_name != "zosboot" {
-        return Err(Error::Validation(
-            "partitioning.bios_boot.gpt_name must be 'zosboot'".into(),
-        ));
+    if cfg.partitioning.bios_boot.gpt_name != GPT_NAME_ZOSBOOT {
+        return Err(Error::Validation(format!(
+            "partitioning.bios_boot.gpt_name must be '{}'",
+            GPT_NAME_ZOSBOOT
+        )));
    }

    // Reserved filesystem labels
-    if cfg.filesystem.vfat.label != "ZOSBOOT" {
-        return Err(Error::Validation(
-            "filesystem.vfat.label must be 'ZOSBOOT'".into(),
-        ));
+    if cfg.filesystem.vfat.label != LABEL_ZOSBOOT {
+        return Err(Error::Validation(format!(
+            "filesystem.vfat.label must be '{}'",
+            LABEL_ZOSBOOT
+        )));
    }
-    if cfg.filesystem.btrfs.label != "ZOSDATA" {
-        return Err(Error::Validation(
-            "filesystem.btrfs.label must be 'ZOSDATA'".into(),
-        ));
+    if cfg.filesystem.btrfs.label != LABEL_ZOSDATA {
+        return Err(Error::Validation(format!(
+            "filesystem.btrfs.label must be '{}'",
+            LABEL_ZOSDATA
+        )));
    }
-    if cfg.filesystem.bcachefs.label != "ZOSDATA" {
-        return Err(Error::Validation(
-            "filesystem.bcachefs.label must be 'ZOSDATA'".into(),
-        ));
+    if cfg.filesystem.bcachefs.label != LABEL_ZOSDATA {
+        return Err(Error::Validation(format!(
+            "filesystem.bcachefs.label must be '{}'",
+            LABEL_ZOSDATA
+        )));
    }

    // Mount scheme
@@ -194,7 +188,9 @@ pub fn validate(cfg: &Config) -> Result<()> {
        Topology::Bcachefs2Copy => {}
        Topology::BtrfsRaid1 => {
            // No enforced requirement here beyond presence of two disks at runtime.
-            if cfg.filesystem.btrfs.raid_profile != "raid1" && cfg.filesystem.btrfs.raid_profile != "none" {
+            if cfg.filesystem.btrfs.raid_profile != "raid1"
+                && cfg.filesystem.btrfs.raid_profile != "none"
+            {
                return Err(Error::Validation(
                    "filesystem.btrfs.raid_profile must be 'none' or 'raid1'".into(),
                ));
@@ -216,15 +212,6 @@ fn to_value<T: serde::Serialize>(t: T) -> Result<Value> {
    serde_json::to_value(t).map_err(|e| Error::Other(e.into()))
 }

-fn load_yaml_value(path: &str) -> Result<Value> {
-    let s = fs::read_to_string(path)
-        .map_err(|e| Error::Config(format!("failed to read config file {}: {}", path, e)))?;
-    // Load as generic serde_json::Value for merging flexibility
-    let v: serde_json::Value = serde_yaml::from_str(&s)
-        .map_err(|e| Error::Config(format!("failed to parse YAML {}: {}", path, e)))?;
-    Ok(v)
-}
-
 /// Merge b into a in-place:
 /// - Objects are merged key-by-key (recursively)
 /// - Arrays and scalars replace
@@ -271,7 +258,7 @@ fn cli_overlay_value(cli: &Cli) -> Value {
        root.insert("device_selection".into(), Value::Object(device_selection));
    }

-    // topology override via --topology (avoid moving out of borrowed field)
+    // topology override via --topology (takes precedence over kernel cmdline)
    if let Some(t) = cli.topology.as_ref() {
        root.insert("topology".into(), Value::String(t.to_string()));
    }
@@ -279,56 +266,46 @@ fn cli_overlay_value(cli: &Cli) -> Value {
    Value::Object(root)
 }

-enum KernelConfigSource {
-    Path(String),
-    /// Raw YAML from a data: URL payload after decoding (if base64-encoded).
-    Data(String),
-}
-
-/// Resolve a config from kernel cmdline key `zosstorage.config=`.
-/// Supports:
-/// - absolute paths (e.g., /run/zos.yaml)
-/// - file:/absolute/path
-/// - data:application/x-yaml;base64,BASE64CONTENT
-/// Returns Ok(None) when key absent.
-fn kernel_cmdline_config_source() -> Result<Option<KernelConfigSource>> {
+//// Parse kernel cmdline for topology override.
+//// Accepts `zosstorage.topology=` and legacy alias `zosstorage.topo=`.
+pub fn kernel_cmdline_topology() -> Option<Topology> {
    let cmdline = fs::read_to_string("/proc/cmdline").unwrap_or_default();
    for token in cmdline.split_whitespace() {
-        if let Some(rest) = token.strip_prefix("zosstorage.config=") {
-            let mut val = rest.to_string();
-            // Trim surrounding quotes if any
-            if (val.starts_with('"') && val.ends_with('"')) || (val.starts_with('\'') && val.ends_with('\'')) {
-                val = val[1..val.len() - 1].to_string();
+        let mut val_opt = None;
+        if let Some(v) = token.strip_prefix("zosstorage.topology=") {
+            val_opt = Some(v);
+        } else if let Some(v) = token.strip_prefix("zosstorage.topo=") {
+            val_opt = Some(v);
        }
-            if let Some(path) = val.strip_prefix("file:") {
-                return Ok(Some(KernelConfigSource::Path(path.to_string())));
+        if let Some(mut val) = val_opt {
+            if (val.starts_with('"') && val.ends_with('"'))
+                || (val.starts_with('\'') && val.ends_with('\''))
+            {
+                val = &val[1..val.len() - 1];
            }
-            if let Some(data_url) = val.strip_prefix("data:") {
-                // data:[<mediatype>][;base64],<data>
-                // Find comma separating the header and payload
-                if let Some(idx) = data_url.find(',') {
-                    let (header, payload) = data_url.split_at(idx);
-                    let payload = &payload[1..]; // skip the comma
-                    let is_base64 = header.split(';').any(|seg| seg.eq_ignore_ascii_case("base64"));
-                    let yaml = if is_base64 {
-                        let decoded = base64::engine::general_purpose::STANDARD
-                            .decode(payload.as_bytes())
-                            .map_err(|e| Error::Config(format!("invalid base64 in data: URL: {}", e)))?;
-                        String::from_utf8(decoded)
-                            .map_err(|e| Error::Config(format!("data: URL payload not UTF-8: {}", e)))?
-                    } else {
-                        payload.to_string()
-                    };
-                    return Ok(Some(KernelConfigSource::Data(yaml)));
-                } else {
-                    return Err(Error::Config("malformed data: URL (missing comma)".into()));
+            let val_norm = val.trim();
+            if let Some(t) = parse_topology_token(val_norm) {
+                return Some(t);
            }
        }
-            // Treat as direct path
-            return Ok(Some(KernelConfigSource::Path(val)));
    }
+    None
+}
+
+//// Helper to parse known topology tokens (canonical names only).
+//// Note: underscores are normalized to hyphens prior to matching.
+fn parse_topology_token(s: &str) -> Option<Topology> {
+    let k = s.trim().to_ascii_lowercase().replace('_', "-");
+    match k.as_str() {
+        "btrfs-single" => Some(Topology::BtrfsSingle),
+        "bcachefs-single" => Some(Topology::BcachefsSingle),
+        "dual-independent" => Some(Topology::DualIndependent),
+        "ssd-hdd-bcachefs" => Some(Topology::SsdHddBcachefs),
+        // Canonical single notation for two-copy bcachefs topology
+        "bcachefs-2copy" => Some(Topology::Bcachefs2Copy),
+        "btrfs-raid1" => Some(Topology::BtrfsRaid1),
+        _ => None,
    }
-    Ok(None)
 }

 /// Built-in defaults for the entire configuration (schema version 1).
@@ -354,7 +331,7 @@ fn default_config() -> Config {
            allow_removable: false,
            min_size_gib: 10,
        },
-        topology: Topology::BtrfsSingle,
+        topology: Topology::DualIndependent,
        partitioning: Partitioning {
            alignment_mib: 1,
            require_empty_disks: true,
--- a/src/config/mod.rs
+++ b/src/config/mod.rs
@@ -11,5 +11,5 @@

 pub mod loader;

-pub use loader::{load_and_merge, validate};
 pub use crate::types::*;
+pub use loader::{load_and_merge, validate};
--- a/src/device/discovery.rs
+++ b/src/device/discovery.rs
@@ -186,7 +186,10 @@ pub fn discover(filter: &DeviceFilter) -> Result<Vec<Disk>> {
    discover_with_provider(&provider, filter)
 }

-fn discover_with_provider<P: DeviceProvider>(provider: &P, filter: &DeviceFilter) -> Result<Vec<Disk>> {
+fn discover_with_provider<P: DeviceProvider>(
+    provider: &P,
+    filter: &DeviceFilter,
+) -> Result<Vec<Disk>> {
    let mut candidates = provider.list_block_devices()?;
    // Probe properties if provider needs to enrich
    for d in &mut candidates {
@@ -210,10 +213,15 @@ fn discover_with_provider<P: DeviceProvider>(provider: &P, filter: &DeviceFilter
        .collect();

    if filtered.is_empty() {
-        return Err(Error::Device("no eligible disks found after applying filters".to_string()));
+        return Err(Error::Device(
+            "no eligible disks found after applying filters".to_string(),
+        ));
    }

-    debug!("eligible disks: {:?}", filtered.iter().map(|d| &d.path).collect::<Vec<_>>());
+    debug!(
+        "eligible disks: {:?}",
+        filtered.iter().map(|d| &d.path).collect::<Vec<_>>()
+    );
    Ok(filtered)
 }

@@ -259,9 +267,10 @@ fn read_disk_size_bytes(name: &str) -> Result<u64> {
    let p = sys_block_path(name).join("size");
    let sectors = fs::read_to_string(&p)
        .map_err(|e| Error::Device(format!("read {} failed: {}", p.display(), e)))?;
-    let sectors: u64 = sectors.trim().parse().map_err(|e| {
-        Error::Device(format!("parse sectors for {} failed: {}", name, e))
-    })?;
+    let sectors: u64 = sectors
+        .trim()
+        .parse()
+        .map_err(|e| Error::Device(format!("parse sectors for {} failed: {}", name, e)))?;
    Ok(sectors.saturating_mul(512))
 }

@@ -287,11 +296,7 @@ fn read_optional_string(p: PathBuf) -> Option<String> {
            while s.ends_with('\n') || s.ends_with('\r') {
                s.pop();
            }
-            if s.is_empty() {
-                None
-            } else {
-                Some(s)
-            }
+            if s.is_empty() { None } else { Some(s) }
        }
        Err(_) => None,
    }
@@ -324,9 +329,27 @@ mod tests {
    fn filter_by_size_and_include_exclude() {
        let provider = MockProvider {
            disks: vec![
-                Disk { path: "/dev/sda".into(), size_bytes: 500 * 1024 * 1024 * 1024, rotational: true, model: None, serial: None }, // 500 GiB
-                Disk { path: "/dev/nvme0n1".into(), size_bytes: 128 * 1024 * 1024 * 1024, rotational: false, model: None, serial: None }, // 128 GiB
-                Disk { path: "/dev/loop0".into(), size_bytes: 8 * 1024 * 1024 * 1024, rotational: false, model: None, serial: None }, // 8 GiB pseudo (but mock provider supplies it)
+                Disk {
+                    path: "/dev/sda".into(),
+                    size_bytes: 500 * 1024 * 1024 * 1024,
+                    rotational: true,
+                    model: None,
+                    serial: None,
+                }, // 500 GiB
+                Disk {
+                    path: "/dev/nvme0n1".into(),
+                    size_bytes: 128 * 1024 * 1024 * 1024,
+                    rotational: false,
+                    model: None,
+                    serial: None,
+                }, // 128 GiB
+                Disk {
+                    path: "/dev/loop0".into(),
+                    size_bytes: 8 * 1024 * 1024 * 1024,
+                    rotational: false,
+                    model: None,
+                    serial: None,
+                }, // 8 GiB pseudo (but mock provider supplies it)
            ],
        };

@@ -346,7 +369,13 @@ mod tests {
    fn no_match_returns_error() {
        let provider = MockProvider {
            disks: vec![
-                Disk { path: "/dev/sdb".into(), size_bytes: 50 * 1024 * 1024 * 1024, rotational: true, model: None, serial: None }, // 50 GiB
+                Disk {
+                    path: "/dev/sdb".into(),
+                    size_bytes: 50 * 1024 * 1024 * 1024,
+                    rotational: true,
+                    model: None,
+                    serial: None,
+                }, // 50 GiB
            ],
        };

--- a/src/fs/plan.rs
+++ b/src/fs/plan.rs
@@ -18,21 +18,21 @@
 // ext: dry-run mode to emit mkfs commands without executing (future).
 // REGION: EXTENSION_POINTS-END
 //
- // REGION: SAFETY
- // safety: must not run mkfs on non-empty or unexpected partitions; assume prior validation enforced.
- // safety: ensure labels follow reserved semantics (ZOSBOOT for ESP, ZOSDATA for all data FS).
- // safety: mkfs.btrfs uses -f in apply path immediately after partitioning to handle leftover signatures.
- // REGION: SAFETY-END
+// REGION: SAFETY
+// safety: must not run mkfs on non-empty or unexpected partitions; assume prior validation enforced.
+// safety: ensure labels follow reserved semantics (ZOSBOOT for ESP, ZOSDATA for all data FS).
+// safety: mkfs.btrfs uses -f in apply path immediately after partitioning to handle leftover signatures.
+// REGION: SAFETY-END
 //
 // REGION: ERROR_MAPPING
 // errmap: external mkfs/blkid failures -> crate::Error::Tool with captured stderr.
 // errmap: planning mismatches -> crate::Error::Filesystem with context.
 // REGION: ERROR_MAPPING-END
 //
- // REGION: TODO
- // todo: bcachefs tuning flags mapping from config (compression/checksum/cache_mode) deferred
- // todo: add UUID consistency checks across multi-device filesystems
- // REGION: TODO-END
+// REGION: TODO
+// todo: bcachefs tuning flags mapping from config (compression/checksum/cache_mode) deferred
+// todo: add UUID consistency checks across multi-device filesystems
+// REGION: TODO-END
 //! Filesystem planning and creation for zosstorage.
 //!
 //! Maps partition results to concrete filesystems (vfat, btrfs, bcachefs)
@@ -42,12 +42,12 @@
 //! [fn make_filesystems](plan.rs:1).

 use crate::{
-    Result,
+    Error, Result,
+    partition::{PartRole, PartitionResult},
    types::{Config, Topology},
-    partition::{PartitionResult, PartRole},
    util::{run_cmd, run_cmd_capture, which_tool},
-    Error,
 };
+use std::fs;
 use tracing::{debug, warn};

 /// Filesystem kinds supported by zosstorage.
@@ -96,17 +96,14 @@ pub struct FsResult {
    pub label: String,
 }

-    /// Determine which partitions get which filesystem based on topology.
-    ///
-    /// Rules:
-    /// - ESP partitions => Vfat with label from cfg.filesystem.vfat.label (reserved "ZOSBOOT")
-    /// - Data partitions => Btrfs with label cfg.filesystem.btrfs.label ("ZOSDATA"), unless topology SsdHddBcachefs
-    /// - SsdHddBcachefs => pair one Cache partition (SSD) with one Data partition (HDD) into one Bcachefs FsSpec with devices [cache, data] and label cfg.filesystem.bcachefs.label ("ZOSDATA")
-    /// - DualIndependent/BtrfsRaid1 => map each Data partition to its own Btrfs FsSpec (raid profile concerns are handled later during mkfs)
-pub fn plan_filesystems(
-    parts: &[PartitionResult],
-    cfg: &Config,
-) -> Result<FsPlan> {
+/// Determine which partitions get which filesystem based on topology.
+///
+/// Rules:
+/// - ESP partitions => Vfat with label from cfg.filesystem.vfat.label (reserved "ZOSBOOT")
+/// - Data partitions => Btrfs with label cfg.filesystem.btrfs.label ("ZOSDATA"), unless topology SsdHddBcachefs
+/// - SsdHddBcachefs => pair one Cache partition (SSD) with one Data partition (HDD) into one Bcachefs FsSpec with devices [cache, data] and label cfg.filesystem.bcachefs.label ("ZOSDATA")
+/// - DualIndependent/BtrfsRaid1 => map each Data partition to its own Btrfs FsSpec (raid profile concerns are handled later during mkfs)
+pub fn plan_filesystems(parts: &[PartitionResult], cfg: &Config) -> Result<FsPlan> {
    let mut specs: Vec<FsSpec> = Vec::new();

    // Always map ESP partitions
@@ -121,10 +118,22 @@ pub fn plan_filesystems(
    match cfg.topology {
        Topology::SsdHddBcachefs => {
            // Expect exactly one cache (SSD) and at least one data (HDD). Use the first data for pairing.
-            let cache = parts.iter().find(|p| matches!(p.role, PartRole::Cache))
-                .ok_or_else(|| Error::Filesystem("expected a Cache partition for SsdHddBcachefs topology".to_string()))?;
-            let data = parts.iter().find(|p| matches!(p.role, PartRole::Data))
-                .ok_or_else(|| Error::Filesystem("expected a Data partition for SsdHddBcachefs topology".to_string()))?;
+            let cache = parts
+                .iter()
+                .find(|p| matches!(p.role, PartRole::Cache))
+                .ok_or_else(|| {
+                    Error::Filesystem(
+                        "expected a Cache partition for SsdHddBcachefs topology".to_string(),
+                    )
+                })?;
+            let data = parts
+                .iter()
+                .find(|p| matches!(p.role, PartRole::Data))
+                .ok_or_else(|| {
+                    Error::Filesystem(
+                        "expected a Data partition for SsdHddBcachefs topology".to_string(),
+                    )
+                })?;

            specs.push(FsSpec {
                kind: FsKind::Bcachefs,
@@ -172,8 +181,14 @@ pub fn plan_filesystems(
        }
        Topology::BcachefsSingle => {
            // Single-device bcachefs on the sole Data partition.
-            let data = parts.iter().find(|p| matches!(p.role, PartRole::Data))
-                .ok_or_else(|| Error::Filesystem("expected a Data partition for BcachefsSingle topology".to_string()))?;
+            let data = parts
+                .iter()
+                .find(|p| matches!(p.role, PartRole::Data))
+                .ok_or_else(|| {
+                    Error::Filesystem(
+                        "expected a Data partition for BcachefsSingle topology".to_string(),
+                    )
+                })?;
            specs.push(FsSpec {
                kind: FsKind::Bcachefs,
                devices: vec![data.device_path.clone()],
@@ -193,7 +208,9 @@ pub fn plan_filesystems(
    }

    if specs.is_empty() {
-        return Err(Error::Filesystem("no filesystems to create from provided partitions".to_string()));
+        return Err(Error::Filesystem(
+            "no filesystems to create from provided partitions".to_string(),
+        ));
    }

    Ok(FsPlan { specs })
@@ -214,7 +231,9 @@ pub fn make_filesystems(plan: &FsPlan, cfg: &Config) -> Result<Vec<FsResult>> {
    let blkid_tool = which_tool("blkid")?;

    if blkid_tool.is_none() {
-        return Err(Error::Filesystem("blkid not found in PATH; cannot capture filesystem UUIDs".into()));
+        return Err(Error::Filesystem(
+            "blkid not found in PATH; cannot capture filesystem UUIDs".into(),
+        ));
    }
    let blkid = blkid_tool.unwrap();

@@ -247,7 +266,9 @@ pub fn make_filesystems(plan: &FsPlan, cfg: &Config) -> Result<Vec<FsResult>> {
                    return Err(Error::Filesystem("mkfs.btrfs not found in PATH".into()));
                };
                if spec.devices.is_empty() {
-                    return Err(Error::Filesystem("btrfs requires at least one device".into()));
+                    return Err(Error::Filesystem(
+                        "btrfs requires at least one device".into(),
+                    ));
                }
                // mkfs.btrfs -L LABEL [ -m raid1 -d raid1 (when multi-device/raid1) ] dev1 [dev2 ...]
                let mut args: Vec<String> = vec![mkfs.clone(), "-L".into(), spec.label.clone()];
@@ -287,11 +308,18 @@ pub fn make_filesystems(plan: &FsPlan, cfg: &Config) -> Result<Vec<FsResult>> {
                    return Err(Error::Filesystem("bcachefs not found in PATH".into()));
                };
                if spec.devices.is_empty() {
-                    return Err(Error::Filesystem("bcachefs requires at least one device".into()));
+                    return Err(Error::Filesystem(
+                        "bcachefs requires at least one device".into(),
+                    ));
                }
                // bcachefs format --label LABEL [--replicas=2] dev1 [dev2 ...]
                // Apply replicas policy for Bcachefs2Copy topology (data+metadata replicas = 2)
-                let mut args: Vec<String> = vec![mkfs.clone(), "format".into(), "--label".into(), spec.label.clone()];
+                let mut args: Vec<String> = vec![
+                    mkfs.clone(),
+                    "format".into(),
+                    "--label".into(),
+                    spec.label.clone(),
+                ];
                if matches!(cfg.topology, Topology::Bcachefs2Copy) {
                    args.push("--replicas=2".into());
                }
@@ -328,7 +356,10 @@ fn capture_uuid(blkid: &str, dev: &str) -> Result<String> {
        return Ok(u.clone());
    }
    warn!("blkid did not report UUID for {}", dev);
-   Err(Error::Filesystem(format!("missing UUID in blkid output for {}", dev)))
+    Err(Error::Filesystem(format!(
+        "missing UUID in blkid output for {}",
+        dev
+    )))
 }

 /// Minimal parser for blkid -o export KEY=VAL lines.
@@ -342,6 +373,100 @@ fn parse_blkid_export(s: &str) -> std::collections::HashMap<String, String> {
    map
 }

+/// Probe existing filesystems on the system and return their identities (kind, uuid, label).
+///
+/// This inspects /proc/partitions and uses `blkid -o export` on each device to detect:
+/// - Data filesystems: Btrfs or Bcachefs with label "ZOSDATA"
+/// - ESP filesystems: Vfat with label "ZOSBOOT"
+/// Multi-device filesystems (e.g., btrfs) are de-duplicated by UUID.
+///
+/// Returns:
+/// - Vec<FsResult> with at most one entry per filesystem UUID.
+pub fn probe_existing_filesystems() -> Result<Vec<FsResult>> {
+    let Some(blkid) = which_tool("blkid")? else {
+        return Err(Error::Filesystem(
+            "blkid not found in PATH; cannot probe existing filesystems".into(),
+        ));
+    };
+
+    let content = fs::read_to_string("/proc/partitions")
+        .map_err(|e| Error::Filesystem(format!("/proc/partitions read error: {}", e)))?;
+
+    let mut results_by_uuid: std::collections::HashMap<String, FsResult> =
+        std::collections::HashMap::new();
+
+    for line in content.lines() {
+        let line = line.trim();
+        if line.is_empty() || line.starts_with("major") {
+            continue;
+        }
+        // Format: major minor #blocks name
+        let parts: Vec<&str> = line.split_whitespace().collect();
+        if parts.len() < 4 {
+            continue;
+        }
+        let name = parts[3];
+        // Skip pseudo devices commonly not relevant (loop, ram, zram, fd)
+        if name.starts_with("loop")
+            || name.starts_with("ram")
+            || name.starts_with("zram")
+            || name.starts_with("fd")
+        {
+            continue;
+        }
+
+        let dev_path = format!("/dev/{}", name);
+        // Probe with blkid -o export; ignore non-zero statuses meaning "nothing found"
+        let out = match run_cmd_capture(&[blkid.as_str(), "-o", "export", dev_path.as_str()]) {
+            Ok(o) => o,
+            Err(Error::Tool { status, .. }) if status != 0 => {
+                // No recognizable signature; skip
+                continue;
+            }
+            Err(_) => {
+                // Unexpected failure; skip this device
+                continue;
+            }
+        };
+
+        let map = parse_blkid_export(&out.stdout);
+        let ty = map.get("TYPE").cloned().unwrap_or_default();
+        let label = map
+            .get("ID_FS_LABEL")
+            .cloned()
+            .or_else(|| map.get("LABEL").cloned())
+            .unwrap_or_default();
+        let uuid = map
+            .get("ID_FS_UUID")
+            .cloned()
+            .or_else(|| map.get("UUID").cloned());
+
+        let (kind_opt, expected_label) = match ty.as_str() {
+            "btrfs" => (Some(FsKind::Btrfs), "ZOSDATA"),
+            "bcachefs" => (Some(FsKind::Bcachefs), "ZOSDATA"),
+            "vfat" => (Some(FsKind::Vfat), "ZOSBOOT"),
+            _ => (None, ""),
+        };
+
+        if let (Some(kind), Some(u)) = (kind_opt, uuid) {
+            // Enforce reserved label semantics
+            if !expected_label.is_empty() && label != expected_label {
+                continue;
+            }
+
+            // Deduplicate multi-device filesystems by UUID; record first-seen device
+            results_by_uuid.entry(u.clone()).or_insert(FsResult {
+                kind,
+                devices: vec![dev_path.clone()],
+                uuid: u,
+                label: label.clone(),
+            });
+        }
+    }
+
+    Ok(results_by_uuid.into_values().collect())
+}
+
 #[cfg(test)]
 mod tests_parse {
    use super::parse_blkid_export;
--- a/src/idempotency/mod.rs
+++ b/src/idempotency/mod.rs
@@ -28,14 +28,14 @@
 //! disks are empty before making any destructive changes.

 use crate::{
-    device::Disk,
-    report::{StateReport, REPORT_VERSION},
-    util::{run_cmd_capture, which_tool},
    Error, Result,
+    device::Disk,
+    report::{REPORT_VERSION, StateReport},
+    util::{run_cmd_capture, which_tool},
 };
+use humantime::format_rfc3339;
 use serde_json::json;
 use std::{collections::HashMap, fs, path::Path};
-use humantime::format_rfc3339;
 use tracing::{debug, warn};

 /// Return existing state if system is already provisioned; otherwise None.
@@ -155,7 +155,10 @@ pub fn is_empty_disk(disk: &Disk) -> Result<bool> {

    // Probe with blkid -p
    let Some(blkid) = which_tool("blkid")? else {
-        warn!("blkid not found; conservatively treating {} as not empty", disk.path);
+        warn!(
+            "blkid not found; conservatively treating {} as not empty",
+            disk.path
+        );
        return Ok(false);
    };

@@ -237,7 +240,11 @@ fn is_partition_of(base: &str, name: &str) -> bool {
    if name == base {
        return false;
    }
-    let ends_with_digit = base.chars().last().map(|c| c.is_ascii_digit()).unwrap_or(false);
+    let ends_with_digit = base
+        .chars()
+        .last()
+        .map(|c| c.is_ascii_digit())
+        .unwrap_or(false);
    if ends_with_digit {
        // nvme0n1 -> nvme0n1p1
        if name.starts_with(base) {
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,18 +1,18 @@
 //! Crate root for zosstorage: one-shot disk provisioning utility for initramfs.

 pub mod cli;
-pub mod logging;
 pub mod config;
 pub mod device;
-pub mod partition;
-pub mod fs;
-pub mod mount;
-pub mod report;
-pub mod orchestrator;
-pub mod idempotency;
-pub mod util;
 pub mod errors;
-pub mod types; // top-level types (moved from config/types.rs for visibility)
+pub mod fs;
+pub mod idempotency;
+pub mod logging;
+pub mod mount;
+pub mod orchestrator;
+pub mod partition;
+pub mod report;
+pub mod types;
+pub mod util; // top-level types (moved from config/types.rs for visibility)

 pub use errors::{Error, Result};

--- a/src/logging/mod.rs
+++ b/src/logging/mod.rs
@@ -36,10 +36,10 @@ use std::fs::OpenOptions;
 use std::io::{self};
 use std::sync::OnceLock;
 use tracing::Level;
+use tracing_subscriber::filter::LevelFilter;
 use tracing_subscriber::fmt;
 use tracing_subscriber::prelude::*;
 use tracing_subscriber::registry::Registry;
-use tracing_subscriber::filter::LevelFilter;
 use tracing_subscriber::util::SubscriberInitExt;

 /// Logging options resolved from CLI and/or config.
@@ -116,19 +116,25 @@ pub fn init_logging(opts: &LogOptions) -> Result<()> {
                .with(stderr_layer)
                .with(file_layer)
                .try_init()
-                .map_err(|e| crate::Error::Other(anyhow::anyhow!("failed to set global logger: {}", e)))?;
+                .map_err(|e| {
+                    crate::Error::Other(anyhow::anyhow!("failed to set global logger: {}", e))
+                })?;
        } else {
            // Fall back to stderr-only if file cannot be opened
            Registry::default()
                .with(stderr_layer)
                .try_init()
-                .map_err(|e| crate::Error::Other(anyhow::anyhow!("failed to set global logger: {}", e)))?;
+                .map_err(|e| {
+                    crate::Error::Other(anyhow::anyhow!("failed to set global logger: {}", e))
+                })?;
        }
    } else {
        Registry::default()
            .with(stderr_layer)
            .try_init()
-            .map_err(|e| crate::Error::Other(anyhow::anyhow!("failed to set global logger: {}", e)))?;
+            .map_err(|e| {
+                crate::Error::Other(anyhow::anyhow!("failed to set global logger: {}", e))
+            })?;
    }

    let _ = INIT_GUARD.set(());
--- a/src/main.rs
+++ b/src/main.rs
@@ -52,6 +52,12 @@ fn real_main() -> Result<()> {
    let ctx = orchestrator::Context::new(cfg, log_opts)
        .with_show(cli.show)
        .with_apply(cli.apply)
-        .with_report_path(cli.report.clone());
+        .with_mount_existing(cli.mount_existing)
+        .with_report_current(cli.report_current)
+        .with_report_path(cli.report.clone())
+        .with_topology_from_cli(cli.topology.is_some())
+        .with_topology_from_cmdline(
+            config::loader::kernel_cmdline_topology().is_some() && cli.topology.is_none(),
+        );
    orchestrator::run(&ctx)
 }
--- a/src/mount/ops.rs
+++ b/src/mount/ops.rs
@@ -7,13 +7,13 @@
 // REGION: API-END
 //
 // REGION: RESPONSIBILITIES
-// - Implement mount phase only: plan root mounts under /var/mounts/{UUID}, ensure/plan subvols, and mount subvols to /var/cache/*.
+// - Implement mount phase only: plan root mounts under /var/mounts/{UUID} for data, mount ESP at /boot, ensure/plan subvols, and mount subvols to /var/cache/*.
 // - Use UUID= sources, deterministic primary selection (first FsResult) for dual_independent.
-// - Generate fstab entries only for four subvol targets; exclude runtime root mounts.
+// - Generate fstab entries covering runtime roots (/var/mounts/{UUID}, /boot when present) followed by the four subvol targets.
 // REGION: RESPONSIBILITIES-END
 //
 // REGION: SAFETY
-// - Never mount ESP; only Btrfs/Bcachefs data FS. Root btrfs mounts use subvolid=5 (top-level).
+// - Mount ESP (VFAT) read-write at /boot once; data roots use subvolid=5 (btrfs) or plain (bcachefs).
 // - Create-if-missing subvolumes prior to subvol mounts; ensure directories exist.
 // - Always use UUID= sources; no device paths.
 // - Bcachefs subvolume mounts use option key 'X-mount.subdir={name}' (not 'subvol=').
@@ -36,22 +36,108 @@
 #![allow(dead_code)]

 use crate::{
+    Error, Result,
    fs::{FsKind, FsResult},
    types::Config,
    util::{run_cmd, run_cmd_capture, which_tool},
-    Error, Result,
 };
-use std::fs::{create_dir_all, File};
+use std::collections::HashMap;
+use std::fs::{File, create_dir_all};
 use std::io::Write;
 use std::path::Path;
+use tracing::info;

 const ROOT_BASE: &str = "/var/mounts";
+const BOOT_TARGET: &str = "/boot";
 const TARGET_SYSTEM: &str = "/var/cache/system";
 const TARGET_ETC: &str = "/var/cache/etc";
 const TARGET_MODULES: &str = "/var/cache/modules";
 const TARGET_VM_META: &str = "/var/cache/vm-meta";
 const SUBVOLS: &[&str] = &["system", "etc", "modules", "vm-meta"];

+#[derive(Debug, Clone)]
+struct ExistingMount {
+    source: String,
+    fstype: String,
+    options: String,
+}
+
+fn current_mounts() -> HashMap<String, ExistingMount> {
+    let mut map = HashMap::new();
+    if let Ok(content) = std::fs::read_to_string("/proc/self/mountinfo") {
+        for line in content.lines() {
+            let parts: Vec<&str> = line.split_whitespace().collect();
+            if parts.len() < 7 {
+                continue;
+            }
+            let target = parts[4].to_string();
+            let mount_options = parts[5].to_string();
+            if let Some(idx) = parts.iter().position(|p| *p == "-") {
+                if idx + 2 < parts.len() {
+                    let fstype = parts[idx + 1].to_string();
+                    let source = parts[idx + 2].to_string();
+                    let super_opts = if idx + 3 < parts.len() {
+                        parts[idx + 3].to_string()
+                    } else {
+                        String::new()
+                    };
+                    let combined_options = if super_opts.is_empty() {
+                        mount_options.clone()
+                    } else {
+                        format!("{mount_options},{super_opts}")
+                    };
+                    map.insert(
+                        target,
+                        ExistingMount {
+                            source,
+                            fstype,
+                            options: combined_options,
+                        },
+                    );
+                }
+            }
+        }
+    }
+    map
+}
+
+fn source_matches_uuid(existing_source: &str, uuid: &str) -> bool {
+    if existing_source == format!("UUID={}", uuid) {
+        return true;
+    }
+    if let Some(existing_uuid) = existing_source.strip_prefix("UUID=") {
+        return existing_uuid == uuid;
+    }
+    if existing_source.starts_with("/dev/") {
+        let uuid_path = Path::new("/dev/disk/by-uuid").join(uuid);
+        if let (Ok(existing_canon), Ok(uuid_canon)) = (
+            std::fs::canonicalize(existing_source),
+            std::fs::canonicalize(&uuid_path),
+        ) {
+            return existing_canon == uuid_canon;
+        }
+    }
+    false
+}
+
+fn disk_of_device(dev: &str) -> Option<String> {
+    let path = Path::new(dev);
+    let name = path.file_name()?.to_str()?;
+    let mut cutoff = name.len();
+    while cutoff > 0 && name.as_bytes()[cutoff - 1].is_ascii_digit() {
+        cutoff -= 1;
+    }
+    if cutoff == name.len() {
+        return Some(dev.to_string());
+    }
+    let mut disk = name[..cutoff].to_string();
+    if disk.ends_with('p') {
+        disk.pop();
+    }
+    let parent = path.parent()?.to_str().unwrap_or("/dev");
+    Some(format!("{}/{}", parent, disk))
+}
+
 #[derive(Debug, Clone)]
 pub struct PlannedMount {
    pub uuid: String,    // UUID string without prefix
@@ -134,11 +220,36 @@ pub fn plan_mounts(fs_results: &[FsResult], _cfg: &Config) -> Result<MountPlan>
        });
    }

-    // Determine primary UUID
-    let primary_uuid = Some(data[0].uuid.clone());
+    let primary = data[0];
+    let primary_uuid = Some(primary.uuid.clone());
+    let primary_disk = primary.devices.first().and_then(|dev| disk_of_device(dev));
+
+    let mut chosen_esp: Option<&FsResult> = None;
+    let mut fallback_esp: Option<&FsResult> = None;
+    for esp in fs_results.iter().filter(|r| matches!(r.kind, FsKind::Vfat)) {
+        if fallback_esp.is_none() {
+            fallback_esp = Some(esp);
+        }
+        if let (Some(ref disk), Some(esp_disk)) = (
+            primary_disk.as_ref(),
+            esp.devices.first().and_then(|dev| disk_of_device(dev)),
+        ) {
+            if esp_disk == **disk {
+                chosen_esp = Some(esp);
+                break;
+            }
+        }
+    }
+    if let Some(esp) = chosen_esp.or(fallback_esp) {
+        root_mounts.push(PlannedMount {
+            uuid: esp.uuid.clone(),
+            target: BOOT_TARGET.to_string(),
+            fstype: fstype_str(esp.kind).to_string(),
+            options: "rw".to_string(),
+        });
+    }

    // Subvol mounts only from primary FS
-    let primary = data[0];
    let mut subvol_mounts: Vec<PlannedSubvolMount> = Vec::new();
    let fstype = fstype_str(primary.kind).to_string();
    // Option key differs per filesystem: btrfs uses subvol=, bcachefs uses X-mount.subdir=
@@ -189,11 +300,37 @@ pub fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>> {
            .map_err(|e| Error::Mount(format!("failed to create dir {}: {}", sm.target, e)))?;
    }

-    let mut results: Vec<MountResult> = Vec::new();
+    let mut results_map: HashMap<String, MountResult> = HashMap::new();
+    let mut existing_mounts = current_mounts();

    // Root mounts
    for pm in &plan.root_mounts {
        let source = format!("UUID={}", pm.uuid);
+        if let Some(existing) = existing_mounts.get(pm.target.as_str()) {
+            if source_matches_uuid(&existing.source, &pm.uuid) {
+                info!(
+                    "mount::apply_mounts: target {} already mounted; skipping",
+                    pm.target
+                );
+                let existing_fstype = existing.fstype.clone();
+                let existing_options = existing.options.clone();
+                results_map
+                    .entry(pm.target.clone())
+                    .or_insert_with(|| MountResult {
+                        source: source.clone(),
+                        target: pm.target.clone(),
+                        fstype: existing_fstype,
+                        options: existing_options,
+                    });
+                continue;
+            } else {
+                return Err(Error::Mount(format!(
+                    "target {} already mounted by {} (expected UUID={})",
+                    pm.target, existing.source, pm.uuid
+                )));
+            }
+        }
+
        let args = [
            mount_tool.as_str(),
            "-t",
@@ -204,12 +341,23 @@ pub fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>> {
            pm.target.as_str(),
        ];
        run_cmd(&args)?;
-        results.push(MountResult {
+        existing_mounts.insert(
+            pm.target.clone(),
+            ExistingMount {
+                source: source.clone(),
+                fstype: pm.fstype.clone(),
+                options: pm.options.clone(),
+            },
+        );
+        results_map.insert(
+            pm.target.clone(),
+            MountResult {
                source,
                target: pm.target.clone(),
                fstype: pm.fstype.clone(),
                options: pm.options.clone(),
-        });
+            },
+        );
    }

    // Subvolume creation (create-if-missing) and mounts for the primary
@@ -245,14 +393,18 @@ pub fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>> {
                if !exists {
                    // Create subvolume
                    let subvol_path = format!("{}/{}", root, sm.name);
-                    let args = [btrfs_tool.as_str(), "subvolume", "create", subvol_path.as_str()];
+                    let args = [
+                        btrfs_tool.as_str(),
+                        "subvolume",
+                        "create",
+                        subvol_path.as_str(),
+                    ];
                    run_cmd(&args)?;
                }
            }
        } else if primary_kind == "bcachefs" {
-            let bcachefs_tool = which_tool("bcachefs")?.ok_or_else(|| {
-                Error::Mount("required tool 'bcachefs' not found in PATH".into())
-            })?;
+            let bcachefs_tool = which_tool("bcachefs")?
+                .ok_or_else(|| Error::Mount("required tool 'bcachefs' not found in PATH".into()))?;
            for sm in &plan.subvol_mounts {
                if &sm.uuid != primary_uuid {
                    continue;
@@ -279,6 +431,31 @@ pub fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>> {
    // Subvol mounts
    for sm in &plan.subvol_mounts {
        let source = format!("UUID={}", sm.uuid);
+        if let Some(existing) = existing_mounts.get(sm.target.as_str()) {
+            if source_matches_uuid(&existing.source, &sm.uuid) {
+                info!(
+                    "mount::apply_mounts: target {} already mounted; skipping",
+                    sm.target
+                );
+                let existing_fstype = existing.fstype.clone();
+                let existing_options = existing.options.clone();
+                results_map
+                    .entry(sm.target.clone())
+                    .or_insert_with(|| MountResult {
+                        source: source.clone(),
+                        target: sm.target.clone(),
+                        fstype: existing_fstype,
+                        options: existing_options,
+                    });
+                continue;
+            } else {
+                return Err(Error::Mount(format!(
+                    "target {} already mounted by {} (expected UUID={})",
+                    sm.target, existing.source, sm.uuid
+                )));
+            }
+        }
+
        let args = [
            mount_tool.as_str(),
            "-t",
@@ -289,14 +466,28 @@ pub fn apply_mounts(plan: &MountPlan) -> Result<Vec<MountResult>> {
            sm.target.as_str(),
        ];
        run_cmd(&args)?;
-        results.push(MountResult {
+        existing_mounts.insert(
+            sm.target.clone(),
+            ExistingMount {
+                source: source.clone(),
+                fstype: sm.fstype.clone(),
+                options: sm.options.clone(),
+            },
+        );
+        results_map.insert(
+            sm.target.clone(),
+            MountResult {
                source,
                target: sm.target.clone(),
                fstype: sm.fstype.clone(),
                options: sm.options.clone(),
-        });
+            },
+        );
    }

+    let mut results: Vec<MountResult> = results_map.into_values().collect();
+    results.sort_by(|a, b| a.target.cmp(&b.target));
+
    Ok(results)
 }

@@ -306,24 +497,26 @@ pub fn maybe_write_fstab(mounts: &[MountResult], cfg: &Config) -> Result<()> {
        return Ok(());
    }

-    // Filter only the four subvol targets
+    // Partition mount results into runtime root mounts and final subvolume targets.
+    let mut root_entries: Vec<&MountResult> = mounts
+        .iter()
+        .filter(|m| m.target.starts_with(ROOT_BASE) || m.target == BOOT_TARGET)
+        .collect();
    let wanted = [TARGET_ETC, TARGET_MODULES, TARGET_SYSTEM, TARGET_VM_META];
-    let mut entries: Vec<&MountResult> = mounts
+    let mut subvol_entries: Vec<&MountResult> = mounts
        .iter()
        .filter(|m| wanted.contains(&m.target.as_str()))
        .collect();

-    // Sort by target path ascending to be deterministic
-    entries.sort_by(|a, b| a.target.cmp(&b.target));
+    // Sort by target path ascending to be deterministic (roots before subvols).
+    root_entries.sort_by(|a, b| a.target.cmp(&b.target));
+    subvol_entries.sort_by(|a, b| a.target.cmp(&b.target));

-    // Compose lines
+    // Compose lines: include all root mounts first, followed by the four subvol targets.
    let mut lines: Vec<String> = Vec::new();
-    for m in entries {
+    for m in root_entries.into_iter().chain(subvol_entries.into_iter()) {
        // m.source already "UUID=..."
-        let line = format!(
-            "{} {} {} {} 0 0",
-            m.source, m.target, m.fstype, m.options
-        );
+        let line = format!("{} {} {} {} 0 0", m.source, m.target, m.fstype, m.options);
        lines.push(line);
    }

--- a/src/orchestrator/run.rs
+++ b/src/orchestrator/run.rs
@@ -43,13 +43,13 @@
 //! - Report generation and write

 use crate::{
-    types::Config,
-    logging::LogOptions,
-    device::{discover, DeviceFilter, Disk},
-    idempotency,
-    partition,
-    fs as zfs,
    Error, Result,
+    device::{DeviceFilter, Disk, discover},
+    fs as zfs, idempotency,
+    logging::LogOptions,
+    partition,
+    report::StateReport,
+    types::{Config, Topology},
 };
 use humantime::format_rfc3339;
 use regex::Regex;
@@ -69,8 +69,16 @@ pub struct Context {
    pub show: bool,
    /// When true, perform destructive actions (apply mode).
    pub apply: bool,
+    /// When true, attempt to mount existing filesystems based on on-disk headers (non-destructive).
+    pub mount_existing: bool,
+    /// When true, emit a report of currently initialized filesystems and mounts (non-destructive).
+    pub report_current: bool,
    /// Optional report path override (when provided by CLI --report).
    pub report_path_override: Option<String>,
+    /// True when topology was provided via CLI (--topology), giving it precedence.
+    pub topo_from_cli: bool,
+    /// True when topology was provided via kernel cmdline, giving it precedence if CLI omitted it.
+    pub topo_from_cmdline: bool,
 }

 impl Context {
@@ -81,7 +89,11 @@ impl Context {
            log,
            show: false,
            apply: false,
+            mount_existing: false,
+            report_current: false,
            report_path_override: None,
+            topo_from_cli: false,
+            topo_from_cmdline: false,
        }
    }

@@ -118,6 +130,56 @@ impl Context {
        self.report_path_override = path;
        self
    }
+
+    /// Enable or disable mount-existing mode (non-destructive).
+    pub fn with_mount_existing(mut self, mount_existing: bool) -> Self {
+        self.mount_existing = mount_existing;
+        self
+    }
+
+    /// Enable or disable reporting of current state (non-destructive).
+    pub fn with_report_current(mut self, report_current: bool) -> Self {
+        self.report_current = report_current;
+        self
+    }
+
+    /// Mark that topology was provided via CLI (--topology).
+    pub fn with_topology_from_cli(mut self, v: bool) -> Self {
+        self.topo_from_cli = v;
+        self
+    }
+
+    /// Mark that topology was provided via kernel cmdline (zosstorage.topology=).
+    pub fn with_topology_from_cmdline(mut self, v: bool) -> Self {
+        self.topo_from_cmdline = v;
+        self
+    }
+}
+#[derive(Debug, Clone, Copy)]
+enum ProvisioningMode {
+    Apply,
+    Preview,
+}
+
+#[derive(Debug, Clone, Copy)]
+enum AutoDecision {
+    Apply,
+    MountExisting,
+}
+
+#[derive(Debug)]
+struct AutoSelection {
+    decision: AutoDecision,
+    fs_results: Option<Vec<zfs::FsResult>>,
+    state: Option<StateReport>,
+}
+#[derive(Debug, Clone, Copy)]
+enum ExecutionMode {
+    ReportCurrent,
+    MountExisting,
+    Apply,
+    Preview,
+    Auto,
 }

 /// Run the one-shot provisioning flow.
@@ -125,57 +187,352 @@ impl Context {
 /// Returns Ok(()) on success and also on success-noop when already provisioned.
 /// Any validation or execution failure aborts with an error.
 pub fn run(ctx: &Context) -> Result<()> {
-    info!("orchestrator: starting run() with topology {:?}", ctx.cfg.topology);
+    info!("orchestrator: starting run()");
+
+    let selected_modes =
+        (ctx.mount_existing as u8) + (ctx.report_current as u8) + (ctx.apply as u8);
+    if selected_modes > 1 {
+        return Err(Error::Validation(
+            "choose only one mode: --mount-existing | --report-current | --apply".into(),
+        ));
+    }
+
+    let preview_requested = ctx.show || ctx.report_path_override.is_some();
+
+    let initial_mode = if ctx.report_current {
+        ExecutionMode::ReportCurrent
+    } else if ctx.mount_existing {
+        ExecutionMode::MountExisting
+    } else if ctx.apply {
+        ExecutionMode::Apply
+    } else if preview_requested {
+        ExecutionMode::Preview
+    } else {
+        ExecutionMode::Auto
+    };
+
+    match initial_mode {
+        ExecutionMode::ReportCurrent => run_report_current(ctx),
+        ExecutionMode::MountExisting => run_mount_existing(ctx, None, None),
+        ExecutionMode::Apply => run_provisioning(ctx, ProvisioningMode::Apply, None),
+        ExecutionMode::Preview => run_provisioning(ctx, ProvisioningMode::Preview, None),
+        ExecutionMode::Auto => {
+            let selection = auto_select_mode(ctx)?;
+            match selection.decision {
+                AutoDecision::MountExisting => {
+                    run_mount_existing(ctx, selection.fs_results, selection.state)
+                }
+                AutoDecision::Apply => {
+                    run_provisioning(ctx, ProvisioningMode::Apply, selection.state)
+                }
+            }
+        }
+    }
+}
+
+fn auto_select_mode(ctx: &Context) -> Result<AutoSelection> {
+    info!("orchestrator: auto-selecting execution mode");
+    let state = idempotency::detect_existing_state()?;
+    let fs_results = zfs::probe_existing_filesystems()?;
+
+    if let Some(state) = state {
+        info!("orchestrator: provisioned state detected; attempting mount-existing flow");
+        return Ok(AutoSelection {
+            decision: AutoDecision::MountExisting,
+            fs_results: if fs_results.is_empty() {
+                None
+            } else {
+                Some(fs_results)
+            },
+            state: Some(state),
+        });
+    }
+
+    if !fs_results.is_empty() {
+        info!(
+            "orchestrator: detected {} filesystem(s) with reserved labels; selecting mount-existing",
+            fs_results.len()
+        );
+        return Ok(AutoSelection {
+            decision: AutoDecision::MountExisting,
+            fs_results: Some(fs_results),
+            state: None,
+        });
+    }
+
+    info!(
+        "orchestrator: no provisioned state or labeled filesystems detected; selecting apply mode (topology={:?})",
+        ctx.cfg.topology
+    );
+
+    Ok(AutoSelection {
+        decision: AutoDecision::Apply,
+        fs_results: None,
+        state: None,
+    })
+}
+
+fn run_report_current(ctx: &Context) -> Result<()> {
+    info!("orchestrator: report-current mode");
+    let fs_results = zfs::probe_existing_filesystems()?;
+
+    // Read all mounts, filtering common system/uninteresting ones
+    let mounts_content = fs::read_to_string("/proc/mounts").unwrap_or_default();
+    let mounts_json: Vec<serde_json::Value> = mounts_content
+        .lines()
+        .filter_map(|line| {
+            let mut it = line.split_whitespace();
+            let source = it.next()?;
+            let target = it.next()?;
+            let fstype = it.next()?;
+            let options = it.next().unwrap_or("");
+            
+            // Skip common pseudo/virtual filesystems and system mounts
+            if source.starts_with("devtmpfs")
+                || source.starts_with("tmpfs")
+                || source.starts_with("proc")
+                || source.starts_with("sysfs")
+                || source.starts_with("cgroup")
+                || source.starts_with("bpf")
+                || source.starts_with("debugfs")
+                || source.starts_with("securityfs")
+                || source.starts_with("mqueue")
+                || source.starts_with("pstore")
+                || source.starts_with("tracefs")
+                || source.starts_with("hugetlbfs")
+                || source.starts_with("efivarfs")
+                || source.starts_with("systemd-1")
+                || target.starts_with("/proc")
+                || target.starts_with("/sys")
+                || target.starts_with("/dev")
+                || target.starts_with("/run")
+                || target.starts_with("/boot")
+                || target.starts_with("/efi")
+                || target.starts_with("/boot/efi")
+            {
+                return None;
+            }
+
+            // Include zosstorage target mounts and general data mounts
+            Some(json!({
+                "source": source,
+                "target": target,
+                "fstype": fstype,
+                "options": options
+            }))
+        })
+        .collect();
+
+    // Read partition information from /proc/partitions
+    let partitions_content = fs::read_to_string("/proc/partitions").unwrap_or_default();
+    let partitions_json: Vec<serde_json::Value> = partitions_content
+        .lines()
+        .filter_map(|line| {
+            let line = line.trim();
+            if line.is_empty() || line.starts_with("major") {
+                return None;
+            }
+            let parts: Vec<&str> = line.split_whitespace().collect();
+            if parts.len() < 4 {
+                return None;
+            }
+            let name = parts[3];
+            // Skip pseudo devices
+            if name.starts_with("loop")
+                || name.starts_with("ram")
+                || name.starts_with("zram")
+                || name.starts_with("fd")
+                || name.starts_with("dm-")
+                || name.starts_with("md")
+            {
+                return None;
+            }
+            let major: u32 = parts[0].parse().ok()?;
+            let minor: u32 = parts[1].parse().ok()?;
+            let size_kb: u64 = parts[2].parse().ok()?;
+            Some(json!({
+                "name": name,
+                "major": major,
+                "minor": minor,
+                "size_kb": size_kb,
+                "size_gib": size_kb / (1024 * 1024)
+            }))
+        })
+        .collect();
+
+    let fs_json: Vec<serde_json::Value> = fs_results
+        .iter()
+        .map(|r| {
+            let kind_str = match r.kind {
+                zfs::FsKind::Vfat => "vfat",
+                zfs::FsKind::Btrfs => "btrfs",
+                zfs::FsKind::Bcachefs => "bcachefs",
+            };
+            json!({
+                "kind": kind_str,
+                "uuid": r.uuid,
+                "label": r.label,
+                "devices": r.devices
+            })
+        })
+        .collect();

-    // 1) Idempotency pre-flight: if already provisioned, optionally emit summary then exit success.
-    match idempotency::detect_existing_state()? {
-        Some(state) => {
-            info!("orchestrator: already provisioned");
-            if ctx.show || ctx.report_path_override.is_some() {
    let now = format_rfc3339(SystemTime::now()).to_string();
-                let state_json = to_value(&state).map_err(|e| {
-                    Error::Report(format!("failed to serialize StateReport: {}", e))
-                })?;
    let summary = json!({
        "version": "v1",
        "timestamp": now,
-                    "status": "already_provisioned",
-                    "state": state_json
+        "status": "observed",
+        "partitions": partitions_json,
+        "filesystems": fs_json,
+        "mounts": mounts_json
    });
-                if ctx.show {
+
+    println!("{}", summary);
+    if let Some(path) = &ctx.report_path_override {
+        fs::write(path, summary.to_string())
+            .map_err(|e| Error::Report(format!("failed to write report to {}: {}", path, e)))?;
+        info!("orchestrator: wrote report-current to {}", path);
+    }
+    Ok(())
+}
+
+fn run_mount_existing(
+    ctx: &Context,
+    fs_results_override: Option<Vec<zfs::FsResult>>,
+    state_hint: Option<StateReport>,
+) -> Result<()> {
+    info!("orchestrator: mount-existing mode");
+    let fs_results = match fs_results_override {
+        Some(results) => results,
+        None => zfs::probe_existing_filesystems()?,
+    };
+    if fs_results.is_empty() {
+        return Err(Error::Mount(
+            "no existing filesystems with reserved labels (ZOSBOOT/ZOSDATA) were found".into(),
+        ));
+    }
+
+    let mplan = crate::mount::plan_mounts(&fs_results, &ctx.cfg)?;
+    let mres = crate::mount::apply_mounts(&mplan)?;
+    crate::mount::maybe_write_fstab(&mres, &ctx.cfg)?;
+
+    if ctx.show || ctx.report_path_override.is_some() || ctx.report_current {
+        let now = format_rfc3339(SystemTime::now()).to_string();
+        let fs_json: Vec<serde_json::Value> = fs_results
+            .iter()
+            .map(|r| {
+                let kind_str = match r.kind {
+                    zfs::FsKind::Vfat => "vfat",
+                    zfs::FsKind::Btrfs => "btrfs",
+                    zfs::FsKind::Bcachefs => "bcachefs",
+                };
+                json!({
+                    "kind": kind_str,
+                    "uuid": r.uuid,
+                    "label": r.label,
+                    "devices": r.devices,
+                })
+            })
+            .collect();
+
+        let mounts_json: Vec<serde_json::Value> = mres
+            .iter()
+            .map(|m| {
+                json!({
+                    "source": m.source,
+                    "target": m.target,
+                    "fstype": m.fstype,
+                    "options": m.options,
+                })
+            })
+            .collect();
+
+        let mut summary = json!({
+            "version": "v1",
+            "timestamp": now,
+            "status": "mounted_existing",
+            "filesystems": fs_json,
+            "mounts": mounts_json,
+        });
+
+        if let Some(state) = state_hint {
+            if let Ok(state_json) = to_value(&state) {
+                if let Some(obj) = summary.as_object_mut() {
+                    obj.insert("state".to_string(), state_json);
+                }
+            }
+        }
+
+        if ctx.show || ctx.report_current {
            println!("{}", summary);
        }
        if let Some(path) = &ctx.report_path_override {
            fs::write(path, summary.to_string())
                .map_err(|e| Error::Report(format!("failed to write report to {}: {}", path, e)))?;
-                    info!("orchestrator: wrote idempotency report to {}", path);
-                }
-            }
-            return Ok(());
-        }
-        None => {
-            debug!("orchestrator: not provisioned; continuing");
+            info!("orchestrator: wrote mount-existing report to {}", path);
        }
    }

-    // 2) Device discovery using compiled filter from config.
+    Ok(())
+}
+
+fn run_provisioning(
+    ctx: &Context,
+    mode: ProvisioningMode,
+    state_hint: Option<StateReport>,
+) -> Result<()> {
+    let preview_outputs = ctx.show || ctx.report_path_override.is_some();
+
+    let mut state_opt = state_hint;
+    if state_opt.is_none() {
+        state_opt = idempotency::detect_existing_state()?;
+    }
+
+    if let Some(state) = state_opt {
+        info!("orchestrator: already provisioned; ensuring mounts are active");
+        return run_mount_existing(ctx, None, Some(state));
+    }
+
    let filter = build_device_filter(&ctx.cfg)?;
    let disks = discover(&filter)?;
    info!("orchestrator: discovered {} eligible disk(s)", disks.len());

-    // 3) Emptiness enforcement: skip in preview mode (--show/--report) to allow planning output.
-    let preview = ctx.show || ctx.report_path_override.is_some();
-    if ctx.cfg.partitioning.require_empty_disks && !preview {
+    if ctx.cfg.partitioning.require_empty_disks {
+        if matches!(mode, ProvisioningMode::Apply) {
            enforce_empty_disks(&disks)?;
            info!("orchestrator: all target disks verified empty");
-    } else if ctx.cfg.partitioning.require_empty_disks && preview {
-        warn!("orchestrator: preview mode detected (--show/--report); skipping empty-disk enforcement");
        } else {
+            warn!(
+                "orchestrator: preview mode detected (--show/--report); skipping empty-disk enforcement"
+            );
+        }
+    } else if matches!(mode, ProvisioningMode::Apply) {
        warn!("orchestrator: require_empty_disks=false; proceeding without emptiness enforcement");
    }

-    // 4) Partition planning (declarative only; application not yet implemented in this step).
-    let plan = partition::plan_partitions(&disks, &ctx.cfg)?;
+    let effective_cfg = {
+        let mut c = ctx.cfg.clone();
+        if !(ctx.topo_from_cli || ctx.topo_from_cmdline) {
+            let auto_topo = if disks.len() == 1 {
+                Topology::BtrfsSingle
+            } else if disks.len() == 2 {
+                Topology::DualIndependent
+            } else {
+                Topology::BtrfsRaid1
+            };
+            if c.topology != auto_topo {
+                info!("orchestrator: topology auto-selected {:?}", auto_topo);
+                c.topology = auto_topo;
+            } else {
+                info!("orchestrator: using configured topology {:?}", c.topology);
+            }
+        } else {
+            info!("orchestrator: using overridden topology {:?}", c.topology);
+        }
+        c
+    };
+
+    let plan = partition::plan_partitions(&disks, &effective_cfg)?;
    debug!(
        "orchestrator: partition plan ready (alignment={} MiB, disks={})",
        plan.alignment_mib,
@@ -185,8 +542,7 @@ pub fn run(ctx: &Context) -> Result<()> {
        debug!("plan for {}: {} part(s)", dp.disk.path, dp.parts.len());
    }

-    // Apply mode: perform destructive partition application now.
-    if ctx.apply {
+    if matches!(mode, ProvisioningMode::Apply) {
        info!("orchestrator: apply mode enabled; applying partition plan");
        let part_results = partition::apply_partitions(&plan)?;
        info!(
@@ -195,34 +551,32 @@ pub fn run(ctx: &Context) -> Result<()> {
            part_results.len()
        );

-        // Filesystem planning and creation
-        let fs_plan = zfs::plan_filesystems(&part_results, &ctx.cfg)?;
-        info!("orchestrator: filesystem plan contains {} spec(s)", fs_plan.specs.len());
-        let fs_results = zfs::make_filesystems(&fs_plan, &ctx.cfg)?;
+        let fs_plan = zfs::plan_filesystems(&part_results, &effective_cfg)?;
+        info!(
+            "orchestrator: filesystem plan contains {} spec(s)",
+            fs_plan.specs.len()
+        );
+        let fs_results = zfs::make_filesystems(&fs_plan, &effective_cfg)?;
        info!("orchestrator: created {} filesystem(s)", fs_results.len());

-        // Mount planning and application
-        let mplan = crate::mount::plan_mounts(&fs_results, &ctx.cfg)?;
+        let mplan = crate::mount::plan_mounts(&fs_results, &effective_cfg)?;
        let mres = crate::mount::apply_mounts(&mplan)?;
-        crate::mount::maybe_write_fstab(&mres, &ctx.cfg)?;
+        crate::mount::maybe_write_fstab(&mres, &effective_cfg)?;
        return Ok(());
    }

-    // Preview-only path
-    info!("orchestrator: pre-flight complete (idempotency checked, devices discovered, plan computed)");
+    info!(
+        "orchestrator: pre-flight complete (idempotency checked, devices discovered, plan computed)"
+    );

-    // Optional: emit JSON summary via --show or write via --report
-    if ctx.show || ctx.report_path_override.is_some() {
-        let summary = build_summary_json(&disks, &plan, &ctx.cfg)?;
+    if preview_outputs {
+        let summary = build_summary_json(&disks, &plan, &effective_cfg)?;
        if ctx.show {
-            // Print compact JSON to stdout
            println!("{}", summary);
        }
        if let Some(path) = &ctx.report_path_override {
-            // Best-effort write (non-atomic for now, pending report::write_report implementation)
-            fs::write(path, summary.to_string()).map_err(|e| {
-                Error::Report(format!("failed to write report to {}: {}", path, e))
-            })?;
+            fs::write(path, summary.to_string())
+                .map_err(|e| Error::Report(format!("failed to write report to {}: {}", path, e)))?;
            info!("orchestrator: wrote summary report to {}", path);
        }
    }
@@ -242,15 +596,13 @@ fn build_device_filter(cfg: &Config) -> Result<DeviceFilter> {
    let mut exclude = Vec::new();

    for pat in &cfg.device_selection.include_patterns {
-        let re = Regex::new(pat).map_err(|e| {
-            Error::Validation(format!("invalid include regex '{}': {}", pat, e))
-        })?;
+        let re = Regex::new(pat)
+            .map_err(|e| Error::Validation(format!("invalid include regex '{}': {}", pat, e)))?;
        include.push(re);
    }
    for pat in &cfg.device_selection.exclude_patterns {
-        let re = Regex::new(pat).map_err(|e| {
-            Error::Validation(format!("invalid exclude regex '{}': {}", pat, e))
-        })?;
+        let re = Regex::new(pat)
+            .map_err(|e| Error::Validation(format!("invalid exclude regex '{}': {}", pat, e)))?;
        exclude.push(re);
    }

@@ -304,7 +656,11 @@ fn role_str(role: partition::PartRole) -> &'static str {
 /// - mount: scheme summary and target template (e.g., "/var/cache/{UUID}")
 ///
 /// This function is non-destructive and performs no probing beyond the provided inputs.
-fn build_summary_json(disks: &[Disk], plan: &partition::PartitionPlan, cfg: &Config) -> Result<serde_json::Value> {
+fn build_summary_json(
+    disks: &[Disk],
+    plan: &partition::PartitionPlan,
+    cfg: &Config,
+) -> Result<serde_json::Value> {
    // Disks summary
    let disks_json: Vec<serde_json::Value> = disks
        .iter()
@@ -340,14 +696,7 @@ fn build_summary_json(disks: &[Disk], plan: &partition::PartitionPlan, cfg: &Con
    }

    // Decide filesystem kinds and planned mountpoints (template) from plan + cfg.topology
-    let topo_str = match cfg.topology {
-        crate::types::Topology::BtrfsSingle => "btrfs_single",
-        crate::types::Topology::BcachefsSingle => "bcachefs_single",
-        crate::types::Topology::DualIndependent => "dual_independent",
-        crate::types::Topology::SsdHddBcachefs => "ssd_hdd_bcachefs",
-        crate::types::Topology::Bcachefs2Copy => "bcachefs2_copy",
-        crate::types::Topology::BtrfsRaid1 => "btrfs_raid1",
-    };
+    let topo_str = cfg.topology.to_string();

    // Count roles across plan to infer filesystems
    let mut esp_count = 0usize;
--- a/src/partition/plan.rs
+++ b/src/partition/plan.rs
@@ -19,12 +19,12 @@
 // ext: device-specific alignment or reserved areas configurable via cfg in the future.
 // REGION: EXTENSION_POINTS-END
 //
- // REGION: SAFETY
- // safety: must verify require_empty_disks before any modification.
- // safety: when UEFI-booted, suppress creating BIOS boot partition to avoid unnecessary ef02 on UEFI systems.
- // safety: must ensure unique partition GUIDs; identical labels are allowed when expected (e.g., ESP ZOSBOOT).
- // safety: must call udev settle after partition table writes.
- // REGION: SAFETY-END
+// REGION: SAFETY
+// safety: must verify require_empty_disks before any modification.
+// safety: when UEFI-booted, suppress creating BIOS boot partition to avoid unnecessary ef02 on UEFI systems.
+// safety: must ensure unique partition GUIDs; identical labels are allowed when expected (e.g., ESP ZOSBOOT).
+// safety: must call udev settle after partition table writes.
+// REGION: SAFETY-END
 //
 // REGION: ERROR_MAPPING
 // errmap: external tool failure -> crate::Error::Tool { tool, status, stderr }.
@@ -44,11 +44,11 @@
 //! [fn apply_partitions](plan.rs:1).

 use crate::{
-    types::{Config, Topology},
-    device::Disk,
-    util::{run_cmd, run_cmd_capture, which_tool, udev_settle, is_efi_boot},
-    idempotency,
    Error, Result,
+    device::Disk,
+    idempotency,
+    types::{Config, Topology},
+    util::{is_efi_boot, run_cmd, run_cmd_capture, udev_settle, which_tool},
 };
 use tracing::{debug, warn};

@@ -117,20 +117,20 @@ pub struct PartitionResult {
    pub device_path: String,
 }

-    /// Compute GPT-only plan per topology and constraints.
-    ///
-    /// Layout defaults:
-    /// - BIOS boot: cfg.partitioning.bios_boot if enabled (size_mib)
-    /// - ESP: cfg.partitioning.esp.size_mib, GPT name cfg.partitioning.esp.gpt_name (typically "zosboot")
-    /// - Data: remainder, GPT name cfg.partitioning.data.gpt_name ("zosdata")
-    /// - Cache (only for SSD/HDD topology): remainder on SSD after boot/ESP, GPT name cfg.partitioning.cache.gpt_name ("zoscache")
-    ///
-    /// Topology mapping:
-    /// - Single: use first eligible disk; create BIOS (opt) + ESP + Data
-    /// - DualIndependent: need at least 2 disks; disk0: BIOS (opt) + ESP + Data, disk1: Data
-    /// - BtrfsRaid1: need at least 2 disks; disk0: BIOS (opt) + ESP + Data, disk1: Data
-    /// - SsdHddBcachefs: need >=1 SSD (rotational=false) and >=1 HDD (rotational=true);
-    ///     SSD: BIOS (opt) + ESP + Cache; HDD: Data
+/// Compute GPT-only plan per topology and constraints.
+///
+/// Layout defaults:
+/// - BIOS boot: cfg.partitioning.bios_boot if enabled (size_mib)
+/// - ESP: cfg.partitioning.esp.size_mib, GPT name cfg.partitioning.esp.gpt_name (typically "zosboot")
+/// - Data: remainder, GPT name cfg.partitioning.data.gpt_name ("zosdata")
+/// - Cache (only for SSD/HDD topology): remainder on SSD after boot/ESP, GPT name cfg.partitioning.cache.gpt_name ("zoscache")
+///
+/// Topology mapping:
+/// - Single: use first eligible disk; create BIOS (opt) + ESP + Data
+/// - DualIndependent: need at least 2 disks; disk0: BIOS (opt) + ESP + Data, disk1: Data
+/// - BtrfsRaid1: need at least 2 disks; disk0: BIOS (opt) + ESP + Data, disk1: Data
+/// - SsdHddBcachefs: need >=1 SSD (rotational=false) and >=1 HDD (rotational=true);
+///     SSD: BIOS (opt) + ESP + Cache; HDD: Data
 pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
    let align = cfg.partitioning.alignment_mib;
    let require_empty = cfg.partitioning.require_empty_disks;
@@ -138,7 +138,9 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
    let add_bios = cfg.partitioning.bios_boot.enabled && !is_efi_boot();

    if disks.is_empty() {
-        return Err(Error::Partition("no disks provided to partition planner".into()));
+        return Err(Error::Partition(
+            "no disks provided to partition planner".into(),
+        ));
    }

    let mut plans: Vec<DiskPlan> = Vec::new();
@@ -164,7 +166,10 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d0.clone(), parts });
+            plans.push(DiskPlan {
+                disk: d0.clone(),
+                parts,
+            });
        }
        Topology::BcachefsSingle => {
            let d0 = &disks[0];
@@ -186,11 +191,16 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d0.clone(), parts });
+            plans.push(DiskPlan {
+                disk: d0.clone(),
+                parts,
+            });
        }
        Topology::DualIndependent => {
            if disks.len() < 2 {
-                return Err(Error::Partition("DualIndependent topology requires at least 2 disks".into()));
+                return Err(Error::Partition(
+                    "DualIndependent topology requires at least 2 disks".into(),
+                ));
            }
            let d0 = &disks[0];
            let d1 = &disks[1];
@@ -214,7 +224,10 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d0.clone(), parts: parts0 });
+            plans.push(DiskPlan {
+                disk: d0.clone(),
+                parts: parts0,
+            });

            // Disk 1: Data only
            let mut parts1 = Vec::new();
@@ -223,11 +236,16 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d1.clone(), parts: parts1 });
+            plans.push(DiskPlan {
+                disk: d1.clone(),
+                parts: parts1,
+            });
        }
        Topology::BtrfsRaid1 => {
            if disks.len() < 2 {
-                return Err(Error::Partition("BtrfsRaid1 topology requires at least 2 disks".into()));
+                return Err(Error::Partition(
+                    "BtrfsRaid1 topology requires at least 2 disks".into(),
+                ));
            }
            let d0 = &disks[0];
            let d1 = &disks[1];
@@ -251,7 +269,10 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d0.clone(), parts: parts0 });
+            plans.push(DiskPlan {
+                disk: d0.clone(),
+                parts: parts0,
+            });

            // Disk 1: Data only (for RAID1)
            let mut parts1 = Vec::new();
@@ -260,11 +281,16 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d1.clone(), parts: parts1 });
+            plans.push(DiskPlan {
+                disk: d1.clone(),
+                parts: parts1,
+            });
        }
        Topology::Bcachefs2Copy => {
            if disks.len() < 2 {
-                return Err(Error::Partition("Bcachefs2Copy topology requires at least 2 disks".into()));
+                return Err(Error::Partition(
+                    "Bcachefs2Copy topology requires at least 2 disks".into(),
+                ));
            }
            let d0 = &disks[0];
            let d1 = &disks[1];
@@ -288,7 +314,10 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d0.clone(), parts: parts0 });
+            plans.push(DiskPlan {
+                disk: d0.clone(),
+                parts: parts0,
+            });

            // Disk 1: Data only
            let mut parts1 = Vec::new();
@@ -297,14 +326,19 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: d1.clone(), parts: parts1 });
+            plans.push(DiskPlan {
+                disk: d1.clone(),
+                parts: parts1,
+            });
        }
        Topology::SsdHddBcachefs => {
            // Choose SSD (rotational=false) and HDD (rotational=true)
-            let ssd = disks.iter().find(|d| !d.rotational)
-                .ok_or_else(|| Error::Partition("SsdHddBcachefs requires an SSD (non-rotational) disk".into()))?;
-            let hdd = disks.iter().find(|d| d.rotational)
-                .ok_or_else(|| Error::Partition("SsdHddBcachefs requires an HDD (rotational) disk".into()))?;
+            let ssd = disks.iter().find(|d| !d.rotational).ok_or_else(|| {
+                Error::Partition("SsdHddBcachefs requires an SSD (non-rotational) disk".into())
+            })?;
+            let hdd = disks.iter().find(|d| d.rotational).ok_or_else(|| {
+                Error::Partition("SsdHddBcachefs requires an HDD (rotational) disk".into())
+            })?;

            // SSD: BIOS (opt) + ESP + Cache remainder
            let mut parts_ssd = Vec::new();
@@ -325,7 +359,10 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.cache.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: ssd.clone(), parts: parts_ssd });
+            plans.push(DiskPlan {
+                disk: ssd.clone(),
+                parts: parts_ssd,
+            });

            // HDD: Data remainder
            let mut parts_hdd = Vec::new();
@@ -334,7 +371,10 @@ pub fn plan_partitions(disks: &[Disk], cfg: &Config) -> Result<PartitionPlan> {
                size_mib: None,
                gpt_name: cfg.partitioning.data.gpt_name.clone(),
            });
-            plans.push(DiskPlan { disk: hdd.clone(), parts: parts_hdd });
+            plans.push(DiskPlan {
+                disk: hdd.clone(),
+                parts: parts_hdd,
+            });
        }
    }

@@ -389,10 +429,17 @@ pub fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>> {
        if let Some(blockdev) = which_tool("blockdev")? {
            let out = run_cmd_capture(&[blockdev.as_str(), "--getss", disk_path])?;
            let s = out.stdout.trim();
-            return s.parse::<u64>()
-                .map_err(|e| Error::Partition(format!("failed to parse sector size from blockdev for {}: {}", disk_path, e)));
+            return s.parse::<u64>().map_err(|e| {
+                Error::Partition(format!(
+                    "failed to parse sector size from blockdev for {}: {}",
+                    disk_path, e
+                ))
+            });
        }
-        warn!("blockdev not found; assuming 512-byte sectors for {}", disk_path);
+        warn!(
+            "blockdev not found; assuming 512-byte sectors for {}",
+            disk_path
+        );
        Ok(512)
    }

@@ -410,20 +457,29 @@ pub fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>> {
                // Format: "First sector: 2048 (at 1024.0 KiB)"
                let val = rest.trim().split_whitespace().next().unwrap_or("");
                if !val.is_empty() {
-                    first = Some(val.parse::<u64>().map_err(|e| Error::Partition(format!("parse first sector: {}", e)))?);
+                    first = Some(
+                        val.parse::<u64>()
+                            .map_err(|e| Error::Partition(format!("parse first sector: {}", e)))?,
+                    );
                }
            } else if let Some(rest) = line.strip_prefix("Last sector:") {
                let val = rest.trim().split_whitespace().next().unwrap_or("");
                if !val.is_empty() {
-                    last = Some(val.parse::<u64>().map_err(|e| Error::Partition(format!("parse last sector: {}", e)))?);
+                    last = Some(
+                        val.parse::<u64>()
+                            .map_err(|e| Error::Partition(format!("parse last sector: {}", e)))?,
+                    );
                }
            }
        }

-        let first = first.ok_or_else(|| Error::Partition("sgdisk -i missing First sector".into()))?;
+        let first =
+            first.ok_or_else(|| Error::Partition("sgdisk -i missing First sector".into()))?;
        let last = last.ok_or_else(|| Error::Partition("sgdisk -i missing Last sector".into()))?;
        if guid.is_empty() {
-            return Err(Error::Partition("sgdisk -i missing Partition unique GUID".into()));
+            return Err(Error::Partition(
+                "sgdisk -i missing Partition unique GUID".into(),
+            ));
        }
        Ok((guid, first, last))
    }
@@ -467,9 +523,12 @@ pub fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>> {

            run_cmd(&[
                sgdisk.as_str(),
-                "-n", n_arg.as_str(),
-                "-t", t_arg.as_str(),
-                "-c", c_arg.as_str(),
+                "-n",
+                n_arg.as_str(),
+                "-t",
+                t_arg.as_str(),
+                "-c",
+                c_arg.as_str(),
                disk_path,
            ])?;
        }
@@ -486,11 +545,7 @@ pub fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>> {

            // Query sgdisk for partition info
            let i_arg = format!("{}", part_num);
-            let info_out = run_cmd_capture(&[
-                sgdisk.as_str(),
-                "-i", i_arg.as_str(),
-                disk_path,
-            ])?;
+            let info_out = run_cmd_capture(&[sgdisk.as_str(), "-i", i_arg.as_str(), disk_path])?;

            let (unique_guid, first_sector, last_sector) = parse_sgdisk_info(&info_out.stdout)?;
            let sectors = if last_sector >= first_sector {
@@ -516,6 +571,9 @@ pub fn apply_partitions(plan: &PartitionPlan) -> Result<Vec<PartitionResult>> {
        }
    }

-    debug!("apply_partitions: created {} partition entries", results.len());
+    debug!(
+        "apply_partitions: created {} partition entries",
+        results.len()
+    );
    Ok(results)
 }
--- a/src/types.rs
+++ b/src/types.rs
@@ -15,8 +15,18 @@
 // - Keep field names and enums stable; update docs/SCHEMA.md when public surface changes.
 // REGION: RESPONSIBILITIES-END

-use serde::{Deserialize, Serialize};
 use clap::ValueEnum;
+use serde::{Deserialize, Serialize};
+
+/// Reserved filesystem labels.
+pub const LABEL_ZOSBOOT: &str = "ZOSBOOT";
+pub const LABEL_ZOSDATA: &str = "ZOSDATA";
+pub const LABEL_ZOSCACHE: &str = "ZOSCACHE";
+
+/// Reserved GPT partition names.
+pub const GPT_NAME_ZOSBOOT: &str = "zosboot";
+pub const GPT_NAME_ZOSDATA: &str = "zosdata";
+pub const GPT_NAME_ZOSCACHE: &str = "zoscache";

 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct LoggingConfig {
@@ -38,7 +48,7 @@ pub struct DeviceSelection {
    pub min_size_gib: u64,
 }

-#[derive(Debug, Clone, Copy, Serialize, Deserialize, ValueEnum)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, ValueEnum)]
 #[serde(rename_all = "snake_case")]
 #[value(rename_all = "snake_case")]
 pub enum Topology {
@@ -55,7 +65,9 @@ pub enum Topology {
    #[value(alias = "ssd-hdd-bcachefs")]
    SsdHddBcachefs,
    /// Multi-device bcachefs with two replicas (data+metadata).
-    #[value(alias = "bcachefs2-copy", alias = "bcachefs-2copy", alias = "bcachefs-2-copy")]
+    /// Canonical token: bcachefs-2copy
+    #[serde(rename = "bcachefs-2copy")]
+    #[value(alias = "bcachefs-2copy")]
    Bcachefs2Copy,
    /// Optional mirrored btrfs across two disks when explicitly requested.
    #[value(alias = "btrfs-raid1")]
@@ -69,7 +81,8 @@ impl std::fmt::Display for Topology {
            Topology::BcachefsSingle => "bcachefs_single",
            Topology::DualIndependent => "dual_independent",
            Topology::SsdHddBcachefs => "ssd_hdd_bcachefs",
-            Topology::Bcachefs2Copy => "bcachefs2_copy",
+            // Canonical single notation for two-copy bcachefs topology
+            Topology::Bcachefs2Copy => "bcachefs-2copy",
            Topology::BtrfsRaid1 => "btrfs_raid1",
        };
        f.write_str(s)
--- a/src/util/mod.rs
+++ b/src/util/mod.rs
@@ -40,8 +40,8 @@
 //! and consistent error handling.

 use crate::{Error, Result};
-use std::process::Command;
 use std::path::Path;
+use std::process::Command;
 use tracing::{debug, warn};

 /// Captured output from an external tool invocation.
@@ -77,9 +77,10 @@ pub fn run_cmd(args: &[&str]) -> Result<()> {
        )));
    }
    debug!(target: "util.run_cmd", "exec: {:?}", args);
-    let output = Command::new(args[0]).args(&args[1..]).output().map_err(|e| {
-        Error::Other(anyhow::anyhow!("failed to spawn {:?}: {}", args, e))
-    })?;
+    let output = Command::new(args[0])
+        .args(&args[1..])
+        .output()
+        .map_err(|e| Error::Other(anyhow::anyhow!("failed to spawn {:?}: {}", args, e)))?;

    let status_code = output.status.code().unwrap_or(-1);
    if !output.status.success() {
@@ -103,9 +104,10 @@ pub fn run_cmd_capture(args: &[&str]) -> Result<CmdOutput> {
        )));
    }
    debug!(target: "util.run_cmd_capture", "exec: {:?}", args);
-    let output = Command::new(args[0]).args(&args[1..]).output().map_err(|e| {
-        Error::Other(anyhow::anyhow!("failed to spawn {:?}: {}", args, e))
-    })?;
+    let output = Command::new(args[0])
+        .args(&args[1..])
+        .output()
+        .map_err(|e| Error::Other(anyhow::anyhow!("failed to spawn {:?}: {}", args, e)))?;
    let status_code = output.status.code().unwrap_or(-1);
    let stdout = String::from_utf8_lossy(&output.stdout).to_string();
    let stderr = String::from_utf8_lossy(&output.stderr).to_string();
Author	SHA1	Message	Date
Jan De Landtsheer	4cd8c54c44	Expand --report-current to show partitions and all mounts (except pseudo-filesystems)	2025-10-20 14:55:38 +02:00
Jan De Landtsheer	224adf06d8	Standardize 2-copy bcachefs topology naming to 'bcachefs-2copy' across code and docs; align parser and Display; update docs and ADR	2025-10-20 14:21:47 +02:00
Jan De Landtsheer	69370a2f53	config: reuse reserved label and GPT name constants	2025-10-13 10:35:31 +02:00
Jan De Landtsheer	3d14f77516	mount: prefer boot disk ESP and run cargo fmt * choose ESP matching the primary data disk when multiple ESPs exist, falling back gracefully for single-disk layouts * keep new helper to normalize device names and reuse the idempotent mount logic * apply cargo fmt across the tree	2025-10-10 14:49:39 +02:00
Jan De Landtsheer	5746e285b2	Mount repeat fixes, update docs	2025-10-10 14:11:52 +02:00
Jan De Landtsheer	cc126d77b4	mount: mount ESP at /boot alongside data runtimes Add /boot root mount planning for VFAT ESP outputs, reuse the idempotent mount logic to skip duplicates, and ensure /etc/fstab includes both /var/mounts/{UUID} and the ESP when enabled.	2025-10-10 10:11:58 +02:00
Jan De Landtsheer	285adeead4	mount: ensure idempotent results and persist runtime roots * read /proc/self/mountinfo to detect already mounted targets and reuse their metadata * reject conflicting mounts by source, allowing reruns without duplicating entries * return mount results sorted by target for deterministic downstream behavior * write subvolume and /var/mounts/{UUID} entries to fstab when requested	2025-10-10 10:07:48 +02:00
Jan De Landtsheer	c8b76a2a3d	Refine default orchestration flow and documentation - Document defaults-only configuration, kernel topology override, and deprecated CLI flags in README - Mark schema doc as deprecated per ADR-0002 - Warn that --topology/--config are ignored; adjust loader/main/context flow - Refactor orchestrator run() to auto-select mount/apply, reuse state when already provisioned, and serialize topology via Display - Add Callgraph/FUNCTION_LIST/ADR docs tracking the new behavior - Derive Eq for Topology to satisfy updated CLI handling	2025-10-09 16:51:12 +02:00
Jan De Landtsheer	d374176c0b	feat(orchestrator,cli,config,fs): implement 3 modes, CLI-first precedence, kernel topo, defaults - Orchestrator: - Add mutually exclusive modes: --mount-existing, --report-current, --apply - Wire mount-existing/report-current flows and JSON summaries - Reuse mount planning/application; never mount ESP - Context builders for new flags (see: src/orchestrator/run.rs:1) - CLI: - Add --mount-existing and --report-current flags - Keep -t/--topology (ValueEnum) as before (see: src/cli/args.rs:1) - FS: - Implement probe_existing_filesystems() using blkid to detect ZOSDATA/ZOSBOOT and dedupe by UUID (see: src/fs/plan.rs:1) - Config loader: - Precedence now: CLI flags > kernel cmdline (zosstorage.topo) > built-in defaults - Read kernel cmdline topology only if CLI didn’t set -t/--topology - Default topology set to DualIndependent - Do not read /etc config by default in initramfs (see: src/config/loader.rs:1) - Main: - Wire new Context builder flags (see: src/main.rs:1) Rationale: - Enables running from in-kernel initramfs with no config file - Topology can be selected via kernel cmdline (zosstorage.topo) or CLI; CLI has priority	2025-09-30 16:16:51 +02:00
Jan De Landtsheer	b0d8c0bc75	docs: sync with code (topologies, mount scheme, CLI flags, UEFI/BIOS, fstab) and fix relative src links in docs/ to ../src/	2025-09-29 23:24:25 +02:00