Docker CLI Basics

Container Management Commands

Running Containers

The docker run command creates and starts a container from an image:

# Basic run
docker run nginx:1.25

# Detached mode (background)
docker run -d --name web nginx:1.25

# Interactive with shell
docker run -it --name dev ubuntu bash

# Remove container after exit
docker run --rm python:3.12-slim python -c "print('hello')"

# Set environment variables
docker run -e MY_VAR=value -e DEBUG=true myapp:latest

# Limit resources
docker run -d --cpus="1.5" --memory="512m" myapp:latest

# Publish ports
docker run -d -p 8080:80 --name web nginx:1.25

# Mount volume
docker run -d -v mydata:/app/data --name db postgres:16

Common docker run Flags

Listing Containers

# Running containers
docker ps

# All containers (including stopped)
docker ps -a

# Show container sizes
docker ps -s

# Filter by name
docker ps --filter "name=web"

# Custom format
docker ps --format "{{.ID}} {{.Names}} {{.Status}} {{.Ports}}"

Managing Container Lifecycle

# Stop a running container (sends SIGTERM, then SIGKILL after 10s)
docker stop web

# Stop immediately (SIGKILL)
docker kill web

# Start a stopped container
docker start web

# Restart a container
docker restart web

# Pause/unpause (freeze processes with SIGSTOP)
docker pause web
docker unpause web

# Remove a container (must be stopped first)
docker rm web

# Force remove (even if running)
docker rm -f web

# Remove all stopped containers
docker container prune

Image Management Commands

Listing and Inspecting Images

# List local images
docker images

# List all images (including intermediate)
docker images -a

# Show image layers
docker history nginx:1.25

# Inspect image metadata
docker inspect nginx:1.25

# Show image size
docker images --format "{{.Repository}}:{{.Tag}} {{.Size}}"

Pulling and Pushing Images

# Pull from Docker Hub
docker pull nginx:1.25

# Pull from specific registry
docker pull myregistry.com/myapp:v2

# Pull by digest (exact version)
docker pull nginx@sha256:abc123def456...

# Push to registry
docker push myregistry.com/myapp:v2

# Log in to a registry
docker login myregistry.com

Building Images

# Build from Dockerfile in current directory
docker build -t myapp:latest .

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

# Build with build arguments
docker build --build-arg NODE_VERSION=20 -t myapp:latest .

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

# Build and pass build context
docker build -t myapp:latest -f - . <<EOF
FROM node:20
WORKDIR /app
COPY package.json .
RUN npm install
EOF

Tagging and Removing

# Tag an image
docker tag myapp:latest myregistry.com/myapp:v1

# Remove an image
docker rmi myapp:latest

# Remove dangling images (untagged)
docker image prune

# Remove all unused images
docker image prune -a

# Remove by pattern
docker images | grep "none" | awk '{print $3}' | xargs docker rmi

Saving and Loading Images

# Save image to tar file
docker save -o myapp.tar myapp:latest

# Load image from tar file
docker load -i myapp.tar

# Export container filesystem
docker export web > web-container.tar

# Import filesystem as image
docker import web-container.tar myapp:restored

The difference between save/load (preserves image layers and metadata) and export/import (creates a flat filesystem, loses layers) is important — use save/load for image distribution.

Inspection and Debugging Commands

Logs

# View container logs
docker logs web

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

# Show timestamps
docker logs -t web

# Last 100 lines
docker logs --tail 100 web

# Logs since a specific time
docker logs --since 2024-01-15T10:00:00 web

# Logs until a specific time
docker logs --until 2024-01-15T11:00:00 web

Exec (Run Commands Inside Containers)

# Open interactive shell
docker exec -it web bash

# Run single command
docker exec web cat /etc/nginx/nginx.conf

# Run as specific user
docker exec -u root web apt-get update

# Set working directory
docker exec -w /app web ls -la

# Set environment variable
docker exec -e DEBUG=true web env

Inspect and Stats

# Detailed container info (JSON)
docker inspect web

# Get specific field with --format
docker inspect --format '{{.NetworkSettings.IPAddress}}' web
docker inspect --format '{{.State.StartedAt}}' web

# Real-time resource usage
docker stats

# One-time snapshot
docker stats --no-stream

# Specific container
docker stats web

# Custom format
docker stats --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}"

Process and Port Info

# List processes in a container
docker top web

# Show port mappings
docker port web

# Show filesystem changes
docker diff web

# Show container events
docker events --filter container=web

System Commands

# Show Docker system info
docker info

# Show disk usage
docker system df

# Detailed disk usage
docker system df -v

# Remove all unused data (images, containers, networks)
docker system prune

# Remove all unused data including volumes
docker system prune -a --volumes

Copy Files

# Copy from container to host
docker cp web:/var/log/nginx/access.log ./access.log

# Copy from host to container
docker cp ./config.conf web:/etc/nginx/conf.d/

Network and Volume Commands

Network Management

# List networks
docker network ls

# Create a network
docker network create --driver bridge mynet

# Create with subnet
docker network create --subnet 172.18.0.0/16 mynet

# Inspect network
docker network inspect mynet

# Connect container to network
docker network connect mynet web

# Connect with alias
docker network connect --alias db mynet web

# Disconnect network
docker network disconnect mynet web

# Remove network
docker network rm mynet

# Remove unused networks
docker network prune

Volume Management

# List volumes
docker volume ls

# Create a volume
docker volume create mydata

# Inspect volume
docker volume inspect mydata

# Remove a volume
docker volume rm mydata

# Remove unused volumes
docker volume prune

# Use volume with container
docker run -d -v mydata:/var/lib/postgresql/data postgres:16

# Read-only volume
docker run -d -v myconfig:/etc/nginx/conf.d:ro nginx:1.25

# Bind mount (host directory)
docker run -d -v /host/path:/container/path myapp:latest

Docker Compose CLI

# Start services (foreground)
docker compose up

# Start in background
docker compose up -d

# Stop services
docker compose down

# Stop and remove volumes
docker compose down -v

# Rebuild images
docker compose up --build

# View logs
docker compose logs

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

# Execute command in service
docker compose exec web bash