Docker Manager Skill

Docker container and image management.

When to Use

• Start/stop containers

• View container logs

• Inspect container status

• Manage Docker images

• Debug container issues

Container Management

List Containers

List running containers

docker ps

List all containers (including stopped)

docker ps -a

List with size

docker ps -as

Filter containers

docker ps --filter "status=exited" docker ps --filter "name=web"

Start/Stop Containers

Start container

docker start my-container

Stop container

docker stop my-container

Restart container

docker restart my-container

Stop all running containers

docker stop $(docker ps -q)

Kill container (force stop)

docker kill my-container

Remove Containers

Remove stopped container

docker rm my-container

Remove running container (force)

docker rm -f my-container

Remove all stopped containers

docker container prune -f

Remove all containers

docker rm $(docker ps -aq)

Logs & Debugging

View Logs

View logs

docker logs my-container

Follow logs

docker logs -f my-container

View last N lines

docker logs --tail 100 my-container

View with timestamp

docker logs -t my-container

Combine flags

docker logs --tail 50 -f --timestamps my-container

Inspect Container

Get container info

docker inspect my-container

Get specific field

docker inspect -f '{{.State.Status}}' my-container docker inspect -f '{{.NetworkSettings.IPAddress}}' my-container docker inspect -f '{{.Config.Env}}' my-container

Execute Commands

Run command in container

docker exec my-container ls -la

Interactive shell

docker exec -it my-container /bin/bash

Run as different user

docker exec -u root my-container /bin/bash

Container Stats

Real-time stats

docker stats

Stats for specific container

docker stats my-container

Stats with no streaming

docker stats --no-stream my-container

Image Management

List Images

List all images

docker images

List with size

docker images -a

Filter images

docker images --filter "dangling=true"

Pull/Push Images

Pull image

docker pull ubuntu:latest

Pull specific tag

docker pull nginx:alpine

Push image

docker push myregistry/myimage:latest

Remove Images

Remove image

docker rmi my-image:latest

Remove dangling images

docker image prune -f

Remove all unused images

docker image prune -a -f

Docker Compose

Common Commands

Start services

docker-compose up -d

Stop services

docker-compose down

View logs

docker-compose logs -f

Rebuild and start

docker-compose up -d --build

Scale service

docker-compose up -d --scale web=3

Run single service

docker-compose run web bash

Network Management

List Networks

List networks

docker network ls

Inspect network

docker network inspect bridge

Create Network

Create bridge network

docker network create my-network

Create with subnet

docker network create --subnet 172.20.0.0/16 my-network

Volume Management

List Volumes

List volumes

docker volume ls

Inspect volume

docker volume inspect my-volume

Create/Remove Volumes

Create volume

docker volume create my-volume

Remove volume

docker volume rm my-volume

Remove unused volumes

docker volume prune -f

Examples

Quick Container Health Check

#!/bin/bash

Check all container health

for container in $(docker ps --format '{{.Names}}'); do status=$(docker inspect -f '{{.State.Health.Status}}' $container 2>/dev/null || echo "no-healthcheck") running=$(docker inspect -f '{{.State.Running}}' $container) echo "$container: running=$running health=$status" done

Cleanup Script

#!/bin/bash

Docker cleanup script

Stop all containers

docker stop $(docker ps -q)

Remove all containers

docker rm $(docker ps -aq)

Remove all images

docker rmi $(docker images -q)

Remove all volumes

docker volume prune -f

Remove all networks (except default)

docker network prune -f

Monitor Resource Usage

Watch container stats

watch -n 1 'docker stats --no-stream --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}"'

Docker Compose Example

version: '3.8' services: web: image: nginx:alpine ports: - "80:80" volumes: - ./html:/usr/share/nginx/html:ro environment: - NGINX_HOST=localhost restart: unless-stopped

api: build: ./api ports: - "3000:3000" environment: - DATABASE_URL=postgres://db:5432/app depends_on: - db

db: image: postgres:15 volumes: - db-data:/var/lib/postgresql/data restart: unless-stopped

volumes: db-data:

Notes

• Use docker system df to see disk usage

• Use docker system prune for general cleanup

• Consider using --restart unless-stopped for production containers

• Use volumes for persistent data

• Use networks for inter-container communication