Bits of .NET

⚙️ Init Containers = Setup Tasks

Apps need setup before start. Init containers run before main containers. Database migrations, permissions, downloads.

📝 Init Container Basics

apiVersion: v1
kind: Pod
metadata:
    name: app-with-init
spec:
    initContainers:
    - name: init-db
        image: busybox
        command: ['sh', '-c', 'echo "Initializing database..." && sleep 5']
    - name: init-permissions
        image: busybox
        command: ['sh', '-c', 'chmod -R 777 /data']
    containers:
    - name: main-app
        image: myapp:latest
        volumeMounts:
        - name: data
            mountPath: /data
    volumes:
    - name: data
        emptyDir: {}

🎯 Init Container Examples

# Database migration
apiVersion: apps/v1
kind: Deployment
metadata:
    name: app
spec:
    replicas: 1
    template:
        spec:
            initContainers:
            - name: migrate-db
                image: myapp:migration
                env:
                - name: DB_HOST
                    value: postgres-service
                command: ['sh', '-c', 'npm run migrate']
            containers:
            - name: app
                image: myapp:latest
                env:
                - name: DB_HOST
                    value: postgres-service

# Download assets
apiVersion: v1
kind: Pod
metadata:
    name: app
spec:
    initContainers:
    - name: download-assets
        image: curlimages/curl
        command: ['sh', '-c', 'curl -o /assets/data.json https://example.com/data.json']
        volumeMounts:
        - name: assets
            mountPath: /assets
    containers:
    - name: app
        image: myapp:latest
        volumeMounts:
        - name: assets
            mountPath: /app/assets
    volumes:
    - name: assets
        emptyDir: {}

# Wait for service
apiVersion: v1
kind: Pod
metadata:
    name: app
spec:
    initContainers:
    - name: wait-for-db
        image: busybox
        command: ['sh', '-c', 'until nc -z postgres-service 5432; do echo "Waiting for database..."; sleep 2; done']
    containers:
    - name: app
        image: myapp:latest

💡 Init Container Tips

• Use for database migrations
• Use for asset downloads
• Use for permission setup
• Use for waiting on dependencies
• Run in order, one at a time