Image Management

List Images

docker images
docker images --digests
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.ID}}\t{{.Size}}"

Inspect an Image

docker image inspect <image>
docker history <image>

Remove Images

docker image rm <image_name_or_id>
docker image rm -f <image_name_or_id>   # Force remove

Remove Dangling (untagged) Images

docker image prune -f

Remove Unused Images (Use With Caution)

docker image prune -a

Remove All Images (Extremely Dangerous)

docker rmi -f $(docker images -q)

Building Images

Basic Build

docker build -t myapp:v1.3.17 .

Tag Multiple Versions in One Build

docker build -t myapp:latest -t myapp:${BUILD_NUMBER} .

Disable Cache (Only for Debugging)

docker build --no-cache -t myapp:latest .

Enable BuildKit (Recommended)

DOCKER_BUILDKIT=1 docker build -t myapp:latest .

Multi-Stage Build (Best Practice for Smaller Images)

• Use a builder stage

• Copy only compiled artifacts into a slim runtime image

• Avoid shipping development dependencies

Container Management

List Containers

docker ps
docker ps -a
docker ps --no-trunc

Run a Container

docker run -d --name myapp -p 8080:80 myapp:latest

Common Run Flags

• -d Run detached

• -p host:container Port mapping

• -e KEY=VALUE Set environment variables

• --name Assign name

• --restart unless-stopped Restart policy (recommended for production)

• --mount type=volume,src=...,dst=... Recommended volume syntax

Lifecycle Commands

docker start <container>
docker stop <container>
docker restart <container>
docker rm <container>

Remove All Stopped Containers

docker container prune -f

Logging (Critical for Production Stability)

Docker’s default json-file logging driver can grow indefinitely if not configured.

Uncontrolled logs can consume disk space and crash servers.

Recommended Global Log Rotation

Edit or create:

sudo nano /etc/docker/daemon.json

Add:

{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "50m",
    "max-file": "3"
  }
}

Restart Docker:

sudo systemctl restart docker

Result:

• Each log file max size: 50MB

• Max files per container: 3

• Total max log size per container: ~150MB

Note: Applies only to newly created containers.

Per-Container Log Configuration (Jenkins / docker run)

docker run -d \
  --log-driver json-file \
  --log-opt max-size=50m \
  --log-opt max-file=3 \
  myapp:latest

View Logs

docker logs <container>
docker logs -f <container>
docker logs --tail 200 <container>
docker logs --since 1h <container>

Emergency Log Cleanup (Safe)

This clears log history without affecting data:

truncate -s 0 /var/lib/docker/containers/<container-id>/*-json.log

Find Large Log Files

du -sh /var/lib/docker/containers/*/*-json.log 2>/dev/null | sort -hr | head

Volume Management (Persistent Data)

List Volumes

docker volume ls

Inspect Volume

docker volume inspect <volume>

Create Volume

docker volume create mydata

Remove Unused Volumes (Dangerous)

docker volume prune -f

Only run if you are certain volumes are not needed.

Network Management

List Networks

docker network ls

Inspect Network

docker network inspect <network>

Connect Container to Network

docker network connect <network> <container>

Monitoring and Debugging

Real-Time Resource Usage

docker stats

Inspect Container

docker inspect <container>

Access Running Container

docker exec -it <container> /bin/bash

Disk Usage & overlay2 Management

Check Docker Disk Usage

docker system df
docker system df -v

Check overlay2 Size

du -sh /var/lib/docker/overlay2
du -h --max-depth=1 /var/lib/docker/overlay2 | sort -hr | head

Check Container Log Usage

du -sh /var/lib/docker/containers/*

Safe Cleanup Strategy (Production-Friendly)

Remove Build Cache

Remove Dangling Images

docker image prune -f

Remove Unused Containers

docker container prune -f

Remove Everything Unused (High Risk)

docker system prune -a

Production Hardening Recommendations

1. Always enable log rotation.

2. Avoid using --no-cache in CI unless debugging.

3. Use multi-stage builds.

4. Use unique version tags for rollback capability.

5. Monitor disk usage regularly.

6. Avoid docker system prune -a in production without verification.

7. Use restart policies for critical services.

8. Separate persistent data using volumes.

9. Monitor container logs for abnormal growth.

10. Audit overlay2 usage periodically.