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Maxime Van Hees
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alpine-cloud_hypervisor.md
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alpine-cloud_hypervisor.md
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# How to Install and Run Alpine Linux with Cloud Hypervisor
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This guide walks you through installing Alpine Linux into a QCOW2 disk image using QEMU, and then running that image with [Cloud Hypervisor](https://github.com/cloud-hypervisor/cloud-hypervisor). It includes all the steps you’ll need, from creating the disk, performing the OS install, preparing kernel/initramfs, and finally running the VM with Cloud Hypervisor.
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---
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## **Goal**
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- **Install Alpine Linux into a disk image using QEMU**
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- **Extract the installed kernel and initramfs from the disk**
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- **Boot the VM with Cloud Hypervisor, using direct kernel/initramfs boot**
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---
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## **Prerequisites**
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- Ubuntu (or Debian-based) host
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- `sudo` privileges
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---
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## **Instructions**
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### 1. **Install required tools**
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```sh
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sudo apt update
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sudo apt install -y qemu-utils wget curl qemu-system-x86 libguestfs-tools
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```
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### 2. **Download Cloud Hypervisor binary**
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```sh
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wget https://github.com/cloud-hypervisor/cloud-hypervisor/releases/download/v47.0/cloud-hypervisor-static
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chmod +x cloud-hypervisor-static
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```
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### 3. **Download Alpine Linux ISO**
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We will download the `alpine-virt` ISO, which is similar to the standard ISO but has a slimmed down kernel and is optimized for virtual systems.
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```sh
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wget https://dl-cdn.alpinelinux.org/alpine/v3.22/releases/x86_64/alpine-virt-3.22.1-x86_64.iso
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```
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### 4. **Create a blank disk image**
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The command below will create a blank disk image called `alpine-vm.qcow2` with a size of 2GB.
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```sh
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qemu-img create -f qcow2 alpine-vm.qcow2 2G
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```
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### 5. **Install Alpine into the disk image**
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> **NOTE:** _Cloud Hypervisor does not emulate legacy BIOS/UEFI, so we use QEMU for the initial install._
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```sh
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qemu-system-x86_64 -m 1024M \
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-cdrom alpine-standard-3.22.1-x86_64.iso \
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-drive file=alpine-vm.qcow2,format=qcow2 \
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-boot d \
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-net nic -net user,hostfwd=tcp::2222-:22 \
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-nographic
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```
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- **Inside the VM:**
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- Log in as `root` (no password by default).
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- Run `setup-alpine` and complete the installation steps.
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### 6. **(Optional): Boot into the installed Alpine system with QEMU**
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1. Boot into VM:
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```sh
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qemu-system-x86_64 \
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-m 1024M \
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-drive file=alpine-vm.qcow2,format=qcow2 \
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-net nic -net user,hostfwd=tcp::2222-:22 \
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-nographic
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```
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2. Install `curl` and `k3s` on the VM:
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```sh
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apk update
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apk add curl
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curl -sfL https://get.k3s.io | sh -
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```
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### 7. **Enable serial console in Alpine VM**
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Edit the `/etc/update-extlinux.conf` in the VM and set:
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```sh
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serial_port=0
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```
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This ensures the kernel output is available on the serial port, which we use later when launching the VM with Cloud Hypervisor (using the `--serial tty` command line argument).
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### 8. **Extract kernel, initramfs and kernel parameters from the installed disk**
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> **NOTE**: You only need to mount the QCOW2 disk once to get all necessary files and information.
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1. Mount the disk using guestmount
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```sh
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sudo guestmount -a alpine-vm.qcow2 -i /mnt
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```
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2. Copy the kernel and initramfs:
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```sh
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cp /mnt/boot/vmlinuz-lts ./vmlinuz-lts
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cp /mnt/boot/initramfs-lts ./initramfs-lts
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```
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3. Get the kernel command line parameters and the root UUID:
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```sh
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cat /mnt/boot/extlinux.conf
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```
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Look for the `APPEND` line under your boot label (e.g. `LABEL lts`). Example:
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```maxima
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LABEL lts
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MENU DEFAULT
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MENU LABEL Linux lts
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LINUX vmlinuz-lts
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INITRD initramfs-lts
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APPEND root=UUID=8b578951-b524-42b9-a757-67fa90b56ec8 modules=sd-mod,usb-storage,ext4 quiet rootfstype=ext4
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```
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- Copy everything from `root=UUID=...` to the end of the line (after `APPEND`).
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- You will use this as your kernel command line in Cloud Hypervisor
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4. Unmount the disk
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```sh
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guestunmount /mnt
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```
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### 9. Boot Alpine VM with Cloud Hypervisor
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Use the kernel and initramfs you extracted, and set the full kernel command line (adjust UUID and modules as needed):
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```sh
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./cloud-hypervisor-static \
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--kernel ./vmlinuz-lts \
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--initramfs ./initramfs-lts \
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--disk path=alpine-vm.qcow2 \
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--cpus boot=2 \
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--memory size=1024M \
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--net "tap=,mac=,ip=192.168.100.2,mask=255.255.255.0" \
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--serial tty \
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--cmdline "console=ttyS0 root=UUID=8b578951-b524-42b9-a757-67fa90b56ec8 modules=sd-mod,usb-storage,ext4 quiet rootfstype=ext4" \
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--console off
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```
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- **Replace the UUID and modules with your values from step 8.**
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