Docker Essentials 1.0.0

Essential Docker commands and workflows for container management, image operations, and debugging.

Security Scan

This is an instruction-only Docker command reference (cheat-sheet); its requirements and instructions align with its stated purpose and nothing requested or installed appears suspicious.

Purpose & Capability

Name/description, required binary (docker), and provided content are consistent: the skill is a Docker commands/workflows reference and only requires the docker CLI to be present.

Instruction Scope

SKILL.md contains example docker/docker-compose commands and workflows only. It does not instruct reading unrelated files or using external endpoints, or accessing environment variables or config paths beyond typical Docker usage.

Install Mechanism

No install spec and no code files — instruction-only skill. Nothing is downloaded or written to disk by the skill itself.

Credentials

The skill declares no environment variables, credentials, or config paths. Example commands show typical env usage (e.g., docker run -e) but the skill does not request secrets or unrelated credentials.

Persistence & Privilege

always is false and the skill is user-invocable. It does not request persistent/system-level changes or modify other skills. Autonomous invocation is allowed by platform default but is not combined with other red flags here.

Assessment

This is essentially a local Docker command reference and appears coherent. Before using: (1) confirm you trust the agent or user that will execute commands — Docker commands can create containers, mount volumes, and potentially access host data if the daemon is privileged; (2) never paste real secrets into example commands (the SKILL.md uses sample values); (3) avoid running untrusted container images or commands with --privileged or host mounts you don't understand; (4) because the skill can be invoked by the agent, restrict autonomous execution if you don't want commands run without explicit approval; and (5) note the skill source is 'unknown'—if you need provenance, prefer official-sourced guidance or verify the author before allowing broad access.

Docker Essentials

Essential Docker commands for container and image management.

Container Lifecycle

Running containers

# Run container from image
docker run nginx

# Run in background (detached)
docker run -d nginx

# Run with name
docker run --name my-nginx -d nginx

# Run with port mapping
docker run -p 8080:80 -d nginx

# Run with environment variables
docker run -e MY_VAR=value -d app

# Run with volume mount
docker run -v /host/path:/container/path -d app

# Run with auto-remove on exit
docker run --rm alpine echo "Hello"

# Interactive terminal
docker run -it ubuntu bash

Managing containers

# List running containers
docker ps

# List all containers (including stopped)
docker ps -a

# Stop container
docker stop container_name

# Start stopped container
docker start container_name

# Restart container
docker restart container_name

# Remove container
docker rm container_name

# Force remove running container
docker rm -f container_name

# Remove all stopped containers
docker container prune

Container Inspection & Debugging

Viewing logs

# Show logs
docker logs container_name

# Follow logs (like tail -f)
docker logs -f container_name

# Last 100 lines
docker logs --tail 100 container_name

# Logs with timestamps
docker logs -t container_name

Executing commands

# Execute command in running container
docker exec container_name ls -la

# Interactive shell
docker exec -it container_name bash

# Execute as specific user
docker exec -u root -it container_name bash

# Execute with environment variable
docker exec -e VAR=value container_name env

Inspection

# Inspect container details
docker inspect container_name

# Get specific field (JSON path)
docker inspect -f '{{.NetworkSettings.IPAddress}}' container_name

# View container stats
docker stats

# View specific container stats
docker stats container_name

# View processes in container
docker top container_name

Image Management

Building images

# Build from Dockerfile
docker build -t myapp:1.0 .

# Build with custom Dockerfile
docker build -f Dockerfile.dev -t myapp:dev .

# Build with build args
docker build --build-arg VERSION=1.0 -t myapp .

# Build without cache
docker build --no-cache -t myapp .

Managing images

# List images
docker images

# Pull image from registry
docker pull nginx:latest

# Tag image
docker tag myapp:1.0 myapp:latest

# Push to registry
docker push myrepo/myapp:1.0

# Remove image
docker rmi image_name

# Remove unused images
docker image prune

# Remove all unused images
docker image prune -a

Docker Compose

Basic operations

# Start services
docker-compose up

# Start in background
docker-compose up -d

# Stop services
docker-compose down

# Stop and remove volumes
docker-compose down -v

# View logs
docker-compose logs

# Follow logs for specific service
docker-compose logs -f web

# Scale service
docker-compose up -d --scale web=3

Service management

# List services
docker-compose ps

# Execute command in service
docker-compose exec web bash

# Restart service
docker-compose restart web

# Rebuild service
docker-compose build web

# Rebuild and restart
docker-compose up -d --build

Networking

# List networks
docker network ls

# Create network
docker network create mynetwork

# Connect container to network
docker network connect mynetwork container_name

# Disconnect from network
docker network disconnect mynetwork container_name

# Inspect network
docker network inspect mynetwork

# Remove network
docker network rm mynetwork

Volumes

# List volumes
docker volume ls

# Create volume
docker volume create myvolume

# Inspect volume
docker volume inspect myvolume

# Remove volume
docker volume rm myvolume

# Remove unused volumes
docker volume prune

# Run with volume
docker run -v myvolume:/data -d app

System Management

# View disk usage
docker system df

# Clean up everything unused
docker system prune

# Clean up including unused images
docker system prune -a

# Clean up including volumes
docker system prune --volumes

# Show Docker info
docker info

# Show Docker version
docker version

Common Workflows

Development container:

docker run -it --rm \
  -v $(pwd):/app \
  -w /app \
  -p 3000:3000 \
  node:18 \
  npm run dev

Database container:

docker run -d \
  --name postgres \
  -e POSTGRES_PASSWORD=secret \
  -e POSTGRES_DB=mydb \
  -v postgres-data:/var/lib/postgresql/data \
  -p 5432:5432 \
  postgres:15

Quick debugging:

# Shell into running container
docker exec -it container_name sh

# Copy file from container
docker cp container_name:/path/to/file ./local/path

# Copy file to container
docker cp ./local/file container_name:/path/in/container

Multi-stage build:

# Dockerfile
FROM node:18 AS builder
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html

Useful Flags

docker run flags:

• -d: Detached mode (background)
• -it: Interactive terminal
• -p: Port mapping (host:container)
• -v: Volume mount
• -e: Environment variable
• --name: Container name
• --rm: Auto-remove on exit
• --network: Connect to network

docker exec flags:

• -it: Interactive terminal
• -u: User
• -w: Working directory

Tips

• Use .dockerignore to exclude files from build context
• Combine RUN commands in Dockerfile to reduce layers
• Use multi-stage builds to reduce image size
• Always tag your images with versions
• Use --rm for one-off containers
• Use docker-compose for multi-container apps
• Clean up regularly with docker system prune

Documentation

Official docs: https://docs.docker.com/ Dockerfile reference: https://docs.docker.com/engine/reference/builder/ Compose file reference: https://docs.docker.com/compose/compose-file/