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Kubernetes Basics
Essential Kubernetes concepts for deploying applications on Mycelium Cloud.
What is Kubernetes?
Kubernetes (K8s) is a container orchestration platform that automates deploying, scaling, and managing containerized applications. Mycelium Cloud uses K3s, a lightweight Kubernetes distribution perfect for edge and cloud environments.
Why Kubernetes?
- Automated Deployment – Deploy containers across multiple nodes
- Self-Healing – Automatically restart failed containers
- Horizontal Scaling – Scale applications up or down based on demand
- Service Discovery – Automatic DNS and load balancing
- Rolling Updates – Update applications with zero downtime
Core Concepts
Pods
A Pod is the smallest deployable unit in Kubernetes. It represents one or more containers that share:
- Network namespace (same IP address)
- Storage volumes
- Configuration
apiVersion: v1
kind: Pod
metadata:
name: nginx-pod
spec:
containers:
- name: nginx
image: nginx:1.21
ports:
- containerPort: 80
# View pods
kubectl get pods
# View pod details
kubectl describe pod nginx-pod
# View pod logs
kubectl logs nginx-pod
Deployments
A Deployment manages a replicated set of Pods and provides declarative updates.
Features:
- Replica Management – Maintain desired number of pods
- Rolling Updates – Update pods with zero downtime
- Rollback – Revert to previous versions
- Self-Healing – Replace failed pods automatically
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.21
ports:
- containerPort: 80
# Create deployment
kubectl apply -f deployment.yaml
# View deployments
kubectl get deployments
# Scale deployment
kubectl scale deployment nginx-deployment --replicas=5
# Update image
kubectl set image deployment/nginx-deployment nginx=nginx:1.22
Services
Services provide stable network endpoints for accessing pods.
ClusterIP (Default)
Internal-only service, accessible within the cluster:
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
type: ClusterIP
selector:
app: nginx
ports:
- port: 80
targetPort: 80
NodePort
Exposes service on each node's IP at a static port:
apiVersion: v1
kind: Service
metadata:
name: my-service
spec:
type: NodePort
selector:
app: nginx
ports:
- port: 80
targetPort: 80
nodePort: 30080 # 30000-32767
# View services
kubectl get services
# Describe service
kubectl describe service my-service
Namespaces
Namespaces provide logical isolation for resources within a cluster.
# List namespaces
kubectl get namespaces
# Create namespace
kubectl create namespace my-app
# Use namespace
kubectl get pods -n my-app
Storage
Persistent Volumes
PersistentVolumeClaim (PVC) – Request for storage:
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: pvc-data
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 10Gi
Use in pod:
spec:
containers:
- name: app
image: myapp:latest
volumeMounts:
- name: data
mountPath: /data
volumes:
- name: data
persistentVolumeClaim:
claimName: pvc-data
Configuration
ConfigMaps
Store non-sensitive configuration data:
apiVersion: v1
kind: ConfigMap
metadata:
name: app-config
data:
database_url: "postgres://db:5432/mydb"
log_level: "info"
# Create from literal
kubectl create configmap app-config --from-literal=key=value
# View configmaps
kubectl get configmaps
Secrets
Store sensitive data (passwords, tokens, keys):
apiVersion: v1
kind: Secret
metadata:
name: app-secret
type: Opaque
data:
password: cGFzc3dvcmQxMjM= # base64 encoded
# Create secret
kubectl create secret generic app-secret --from-literal=password=password123
# View secrets
kubectl get secrets
Essential kubectl Commands
# Cluster info
kubectl cluster-info
kubectl get nodes
# Pods
kubectl get pods
kubectl get pods -o wide
kubectl describe pod <pod-name>
kubectl logs <pod-name>
kubectl logs -f <pod-name> # Follow logs
kubectl exec -it <pod-name> -- /bin/bash
# Deployments
kubectl get deployments
kubectl scale deployment <name> --replicas=5
kubectl rollout status deployment/<name>
kubectl rollout undo deployment/<name>
# Services
kubectl get services
kubectl describe service <service-name>
# Apply/Delete resources
kubectl apply -f file.yaml
kubectl delete -f file.yaml
# Port forwarding
kubectl port-forward pod/<pod-name> 8080:80
kubectl port-forward service/<service-name> 8080:80
# View all resources
kubectl get all --all-namespaces
# Check events
kubectl get events --sort-by=.metadata.creationTimestamp
Labels and Selectors
Labels are key-value pairs attached to objects:
metadata:
labels:
app: nginx
environment: production
tier: frontend
Selectors query objects by labels:
# Get pods with label
kubectl get pods -l app=nginx
# Get pods with multiple labels
kubectl get pods -l app=nginx,environment=production
Best Practices
-
Use Deployments – Not bare pods, for self-healing and scaling
resources: requests: memory: "64Mi" cpu: "250m" limits: memory: "128Mi" cpu: "500m" -
Use Health Checks – Implement liveness and readiness probes
-
Use Namespaces – Organize resources logically
-
Version Control – Store manifests in Git
-
Use Labels – Tag resources for organization
-
Secrets Management – Never hardcode sensitive data
Next Steps
- Deployment Tutorials – Deploy real applications
- FAQ – Common questions and answers
Additional Resources
- Kubernetes Documentation: kubernetes.io/docs
- kubectl Cheat Sheet: kubernetes.io/docs/reference/kubectl/cheatsheet
- K3s Documentation: docs.k3s.io
:::tip Want to Learn More? This covers the basics to get you started. For advanced topics like StatefulSets, DaemonSets, Ingress, and RBAC, check out the comprehensive Kubernetes documentation linked above. :::