Docker CLI Guide

Docker is a containerization platform that packages applications and dependencies into isolated containers. This guide provides essential workflows and quick references for common Docker operations.

Quick Start

Check Docker installation

docker --version

Run your first container

docker run hello-world

Run interactive container

docker run -it ubuntu bash

Run container in background

docker run -d nginx

List running containers

docker ps

Stop a container

docker stop container_name

Common Workflows

Workflow 1: Build and Run an Application

Create Dockerfile in your project directory

Build image

docker build -t myapp:latest .

Run container with port mapping

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

View logs

docker logs -f myapp

Access container shell

docker exec -it myapp bash

Workflow 2: Development with Hot Reload

Run with volume mount for live code updates

docker run -d
-p 8080:80
-v $(pwd)/src:/app/src
--name myapp-dev
myapp:dev

Watch logs in real-time

docker logs -f myapp-dev

Restart after configuration changes

docker restart myapp-dev

Workflow 3: Multi-Container Application with Docker Compose

Create docker-compose.yml with services

Start all services

docker compose up -d

View service logs

docker compose logs -f

Scale a service

docker compose up -d --scale api=3

Stop all services

docker compose down

Stop and remove volumes

docker compose down -v

Workflow 4: Push Image to Registry

Login to registry

docker login

Build and tag image

docker build -t myapp:latest . docker tag myapp:latest username/myapp:v1.0.0 docker tag myapp:latest username/myapp:latest

Push to registry

docker push username/myapp:v1.0.0 docker push username/myapp:latest

Workflow 5: Debug Container Issues

Check container status

docker ps -a

View container logs

docker logs container_name

Inspect container details

docker inspect container_name

Run interactive shell for debugging

docker run -it --entrypoint /bin/bash myapp:latest

Check container resource usage

docker stats container_name

Decision Tree

When to use which command:

To run a new container: Use docker run with appropriate flags
To execute commands in running container: Use docker exec -it container_name bash
To build an image: Use docker build -t name:tag .
To manage multiple services: Use docker compose up/down
To check container status: Use docker ps or docker ps -a
To view logs: Use docker logs -f container_name
To clean up resources: Use docker system prune or specific prune commands
For detailed command syntax: See Commands Reference
For complex scenarios: See Common Patterns
For troubleshooting: See Troubleshooting Guide

Common Patterns

Running Containers with Options

With environment variables

docker run -e ENV_VAR=value -e API_KEY=secret myapp

With resource limits

docker run --memory=512m --cpus=1.5 myapp

With restart policy

docker run --restart=unless-stopped myapp

With custom network

docker run --network mynetwork myapp

With volume mount

docker run -v mydata:/app/data myapp

Container-to-Container Communication

Create custom network

docker network create myapp-network

Run containers on same network

docker run -d --name database --network myapp-network postgres:15 docker run -d --name app --network myapp-network -p 8080:80 myapp

Containers can now access each other by name

Example: app can connect to database using hostname "database"

Data Persistence

Create named volume

docker volume create myapp-data

Use volume in container

docker run -d -v myapp-data:/var/lib/postgresql/data postgres:15

Backup volume data

docker run --rm
-v myapp-data:/data
-v $(pwd):/backup
ubuntu tar czf /backup/backup.tar.gz /data

Troubleshooting

Common Issues:

Container exits immediately

Solution: Check logs with docker logs container_name
See: Container Won't Start

Can't access service on published port

Quick fix: Verify port mapping with docker port container_name
See: Container Running But Not Accessible

Permission denied errors

Quick fix: Run with user flag docker run -u $(id -u):$(id -g)
See: Permission Denied Errors

Disk space issues

Quick fix: Clean up with docker system prune -a --volumes
See: Disk Space Issues

Network connectivity issues

Quick fix: Check container network with docker network inspect bridge
See: Network Issues

For detailed troubleshooting steps, see the Troubleshooting Guide.

Reference Files

Load as needed for detailed information:

Commands Reference - Complete CLI command documentation with all flags and options. Use when you need exact syntax or flag details for any Docker command.

Common Patterns - Real-world patterns and workflows for development, multi-stage builds, networking, volumes, CI/CD, security, and production deployments. Use for implementing specific workflows or integrations.

Troubleshooting Guide - Detailed error messages, diagnosis steps, and resolution strategies for container, image, network, volume, performance, and system issues. Use when encountering errors or unexpected behavior.

When to use each reference:

Use Commands Reference when you need exact syntax, flag combinations, or comprehensive command documentation
Use Common Patterns for implementing multi-container setups, production configurations, or CI/CD pipelines
Use Troubleshooting when containers won't start, services are unreachable, or you encounter permission/network/performance issues

Resources