Docker CLI A-Z: Your Ultimate Command Line Companion 🚀

G: Are you diving deep into the world of containers, or perhaps looking to sharpen your Docker skills? The Docker Command Line Interface (CLI) is your primary tool for interacting with Docker. While docker might seem simple at first glance, its commands come packed with a plethora of options that unlock powerful functionalities for managing images, containers, networks, and volumes.

This comprehensive guide will take you on an A-Z journey through the most essential Docker CLI commands, detailing their common options and providing practical examples to supercharge your container orchestration game! Get ready to become a Docker CLI master. 💪

🌟 Why Master the Docker CLI?

The Docker CLI is more than just a set of commands; it’s the gateway to efficient development, deployment, and management of containerized applications. Understanding its nuances allows you to:

• Debug Effectively: Quickly inspect container states, logs, and network configurations.
• Automate Workflows: Script complex operations for CI/CD pipelines.
• Optimize Resources: Prune unused resources and monitor system performance.
• Troubleshoot Issues: Pinpoint problems with network connectivity, volume mounts, or container execution.

Let’s embark on this detailed exploration! 🗺️

📚 Core Docker Concepts (Quick Recap)

Before we jump into the commands, a brief refresher on the core components you’ll be interacting with:

• Images: 📦 Read-only templates that contain an application and all its dependencies. Think of them as blueprints for containers.
• Containers: 🏃‍♂️ Runnable instances of an image. They are isolated environments where your applications run.
• Volumes: 💾 Persistent data storage for Docker containers, allowing data to outlive the container itself.
• Networks: 🌐 Enable communication between containers, or between containers and the host machine.

🚀 The A-Z Journey Through Docker CLI Commands

We’ll cover the most frequently used and critical docker commands. While not every single option can be listed, we’ll focus on the ones that bring the most value and flexibility.

1. docker build 🏗️ – Crafting Your Container Images

This command is your go-to for building Docker images from a Dockerfile and a “context” (a set of files at a specified path or URL).

• Syntax: docker build [OPTIONS] PATH | URL | -

• Key Options:

  • --tag, `-t :`: 🏷️ Name and optionally tag the image. It’s good practice to tag your images.
  • `–build-arg =`: 🛠️ Set build-time variables. Useful for passing sensitive information or dynamic values during the build process without embedding them in the `Dockerfile`.
  • --no-cache: 🐢 Build the image without using cached layers. This forces a fresh build.
  • --file, -f <path/to/Dockerfile>: 📝 Specify an alternative Dockerfile path. Default is ./Dockerfile.

• Usage Examples:

  # 1. Build an image from the current directory, tag it 'my-app:latest'
  docker build -t my-app:latest .
  
  # 2. Build and tag with a specific version
  docker build -t my-app:v1.0 .
  
  # 3. Build with a build argument (e.g., passing a version number)
  docker build --build-arg APP_VERSION=2.0 -t my-app:v2.0 .
  
  # 4. Build without using the cache (useful for troubleshooting or ensuring fresh dependencies)
  docker build --no-cache -t my-app:dev .
  
  # 5. Build using a Dockerfile located in a different directory
  docker build -f ./dockerfiles/production.Dockerfile -t my-app:prod .

• Pro Tip: Always include a .dockerignore file! It prevents unnecessary files (like node_modules, .git, venv/) from being sent to the Docker daemon as part of the build context, speeding up your builds and keeping images lean.

2. docker cp 📁➡️📦 / 📦➡️📁 – Copying Files In and Out

This command allows you to copy files/folders between a container’s filesystem and the host machine’s filesystem.

• Syntax:

  • docker cp [OPTIONS] SRC_PATH CONTAINER:DEST_PATH (Host to Container)
  • docker cp [OPTIONS] CONTAINER:SRC_PATH DEST_PATH (Container to Host)

• Key Options:

  • No commonly used specific options, it mainly relies on source and destination paths.

• Usage Examples:

  # 1. Copy a file from your host to a running container's `/app` directory
  docker cp ./config.yaml my-web-app:/app/config.yaml
  
  # 2. Copy an entire directory from your host to a container
  docker cp ./data/ my-database:/var/lib/mysql/data/
  
  # 3. Copy a file from a container to your host's current directory
  docker cp my-web-app:/var/log/nginx/access.log .
  
  # 4. Copy a directory from a container to your host
  docker cp my-database:/etc/mysql/conf.d ./my-mysql-conf/

• Important: The container must be running for docker cp to work reliably.

3. docker exec 🎯 – Running Commands Inside a Container

docker exec allows you to execute a command inside a running container. It’s incredibly useful for debugging, inspecting, or performing administrative tasks within a container without restarting it.

• Syntax: docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

• Key Options:

  • --interactive, -i: 💬 Keep STDIN open even if not attached. Essential for interactive sessions.
  • --tty, -t: 🖥️ Allocate a pseudo-TTY. Often used with -i to get a proper shell experience. (Think docker exec -it).
  • --detach, -d: 🏃‍♀️ Run the command in detached mode (in the background).
  • --user <user|uid>[:<group|gid>]: 👤 Specify the username or UID to run the command as.

• Usage Examples:

  # 1. Get an interactive shell (Bash) inside a running container
  docker exec -it my-web-app bash
  
  # 2. Run a command and exit (e.g., check a file's content)
  docker exec my-web-app cat /app/index.js
  
  # 3. Run a command in the background (detached mode)
  docker exec -d my-database service mysql restart
  
  # 4. Run a command as a specific user (e.g., 'www-data')
  docker exec -it --user www-data my-web-app ls -la /app

4. docker images 🖼️ – Listing Available Images

This command lists the images you have locally stored on your Docker host.

• Syntax: docker images [OPTIONS] [REPOSITORY]

• Key Options:

  • --all, -a: 📦 Show all images, including intermediate images created during multi-stage builds.
  • --quiet, -q: 🤫 Only show numeric IDs. Useful for scripting.
  • --filter, -f <"key=value">: 🔍 Filter output based on conditions (e.g., dangling=true, label=my-label).
  • --format "{{.ID}}\t{{.Repository}}\t{{.Tag}}": 📝 Pretty-print images using Go templates.

• Usage Examples:

  # 1. List all local images
  docker images
  
  # 2. List all images, including intermediate ones
  docker images -a
  
  # 3. List only the IDs of all images
  docker images -q
  
  # 4. Filter for dangling (untagged, unused) images
  docker images -f "dangling=true"
  
  # 5. Filter for images from a specific repository
  docker images my-app
  
  # 6. List images with custom format
  docker images --format "{{.ID}}\t{{.Repository}}\t{{.Tag}}\t{{.Size}}"

5. docker inspect 🔍 – Deep Dive into Docker Objects

docker inspect provides detailed low-level information about Docker objects (containers, images, volumes, networks). It outputs a JSON array, making it perfect for scripting and automated parsing.

• Syntax: docker inspect [OPTIONS] NAME|ID [NAME|ID...]

• Key Options:

  • --format "{{.HostConfig.PortBindings}}": 🎯 Format the output using Go templates, allowing you to extract specific fields.

• Usage Examples:

  # 1. Get all details about a running container
  docker inspect my-web-app
  
  # 2. Get all details about a specific image
  docker inspect nginx:latest
  
  # 3. Extract the IP address of a container
  docker inspect -f '{{.NetworkSettings.IPAddress}}' my-web-app
  
  # 4. Extract port bindings for a container
  docker inspect -f '{{json .NetworkSettings.Ports}}' my-web-app

6. docker logs 📜 – Retrieving Container Logs

This command fetches the logs of a container. It’s crucial for monitoring your application’s behavior and debugging issues.

• Syntax: docker logs [OPTIONS] CONTAINER

• Key Options:

  • --follow, -f: 🔄 Follow log output (like tail -f).
  • `–tail `: 🔢 Output the specified number of lines from the end of the logs.
  • --since <timestamp|duration>: 🕰️ Show logs since a specific timestamp or relative duration (e.g., 10m, 1h).
  • --timestamps, -t: ⏱️ Show timestamps in the logs.

• Usage Examples:

  # 1. View all logs for a container
  docker logs my-web-app
  
  # 2. Follow logs in real-time
  docker logs -f my-web-app
  
  # 3. View the last 50 lines of logs
  docker logs --tail 50 my-web-app
  
  # 4. View logs since 1 hour ago with timestamps
  docker logs --since 1h -t my-web-app

7. docker network 🌐 – Managing Container Networks

The docker network command manages Docker networks, which enable communication between containers and the host.

• Syntax: docker network COMMAND [OPTIONS]

• Common Subcommands:

  • ls: List networks.
  • create: Create a new network.
  • connect: Connect a container to a network.
  • disconnect: Disconnect a container from a network.
  • rm: Remove one or more networks.
  • prune: Remove all unused networks.

• Key Options (for create):

  • `–driver `: 🛠️ Specify the network driver (e.g., `bridge`, `host`, `overlay`). `bridge` is default.
  • `–subnet `: 🌐 Define a subnet for the network.
  • `–gateway `: 🚪 Define the gateway for the network.

• Usage Examples:

  # 1. List all available networks
  docker network ls
  
  # 2. Create a new bridge network
  docker network create --driver bridge my-custom-network
  
  # 3. Inspect a network (e.g., 'bridge' network)
  docker network inspect bridge
  
  # 4. Connect a running container to a network
  docker network connect my-custom-network my-web-app
  
  # 5. Disconnect a container from a network
  docker network disconnect my-custom-network my-web-app
  
  # 6. Remove an unused network
  docker network rm my-custom-network
  
  # 7. Remove all unused networks
  docker network prune

8. docker ps 📋 – Listing Running Containers

This command lists the currently running Docker containers. It’s often the first command you’ll use to check your Docker environment.

• Syntax: docker ps [OPTIONS]

• Key Options:

  • --all, -a: 📝 Show all containers, including stopped ones.
  • --quiet, -q: 🤫 Only display container IDs. Great for scripting.
  • --filter, -f <"key=value">: 🔍 Filter output based on conditions (e.g., status=exited, name=my-app).
  • --format "{{.ID}}\t{{.Names}}\t{{.Status}}\t{{.Ports}}": 📝 Pretty-print containers using Go templates.
  • --size, -s: 📏 Display total file sizes.

• Usage Examples:

  # 1. List all running containers
  docker ps
  
  # 2. List all containers (running and stopped)
  docker ps -a
  
  # 3. List only the IDs of running containers
  docker ps -q
  
  # 4. Filter containers by name (e.g., containing 'web')
  docker ps -f "name=web"
  
  # 5. Filter for exited containers
  docker ps -a -f "status=exited"
  
  # 6. List containers with custom format
  docker ps --format "{{.ID}}\t{{.Names}}\t{{.Status}}\t{{.Image}}"

9. docker pull ⬇️ – Downloading Images

docker pull downloads a Docker image from a registry (default is Docker Hub) to your local machine.

• Syntax: docker pull [OPTIONS] NAME[:TAG|@DIGEST]

• Key Options:

  • No commonly used options beyond the image name and tag.

• Usage Examples:

  # 1. Pull the latest Nginx image
  docker pull nginx:latest
  
  # 2. Pull a specific version of Ubuntu
  docker pull ubuntu:22.04
  
  # 3. Pull an image from a private registry (after logging in)
  docker pull myregistry.com/my-team/my-app:v1.0

10. docker push ⬆️ – Uploading Images

docker push uploads a Docker image from your local machine to a registry (default is Docker Hub). You must be authenticated to push to a private or public repository under your account.

• Syntax: docker push [OPTIONS] NAME[:TAG]

• Key Options:

  • No commonly used options beyond the image name and tag.

• Usage Examples:

  # (First, ensure you are logged in: docker login)
  
  # 1. Push an image to Docker Hub (must be tagged with your username/repo)
  docker push your_dockerhub_username/my-app:latest
  
  # 2. Push a specific version
  docker push your_dockerhub_username/my-app:v1.0
  
  # 3. Push to a private registry
  docker push myregistry.com/my-team/my-app:v2.0

11. docker run ▶️ – The Swiss Army Knife of Docker

This is arguably the most fundamental and versatile command. docker run creates a new container from a specified image and runs a command in it. It has a vast array of options to configure the container’s environment, networking, volumes, and more.

• Syntax: docker run [OPTIONS] IMAGE [COMMAND] [ARG...]

• Key Options (a selection of the most common ones):

  • --detach, -d: 🚪 Run container in the background (detached mode).
  • --publish, `-p :`: 🔗 Publish container ports to the host.
  • --volume, `-v :[:]`: 💾 Mount a host path or named volume into the container.
  • `–name `: 📛 Assign a name to the container. Makes it easier to refer to.
  • `–network `: 🌐 Connect the container to a specific network.
  • --rm: 🗑️ Automatically remove the container when it exits. Great for temporary containers.
  • --interactive, -i & --tty, -t: 💬🖥️ Run container in interactive mode with a pseudo-TTY. Essential for interactive shells (e.g., docker run -it).
  • --env, -e <key=value>: ⚙️ Set environment variables inside the container.
  • --mount type=<bind|volume|tmpfs>,source=<src>,target=<dest>,[options]: 💾 A more explicit and flexible way to mount (preferred over -v for complex mounts).
  • `–restart `: 🔄 Configure a restart policy (e.g., `no`, `on-failure`, `unless-stopped`, `always`).

• Usage Examples:

  # 1. Run a simple Nginx web server in detached mode, mapping port 8080 on host to 80 in container
  docker run -d -p 8080:80 --name my-nginx nginx:latest
  
  # 2. Run an interactive Ubuntu container and get a bash shell
  docker run -it --rm ubuntu:latest bash
  
  # 3. Run a container with a named volume for persistent data
  docker run -d -p 3306:3306 --name my-db -v my-db-data:/var/lib/mysql mysql:8.0
  
  # 4. Run a container and mount a host directory
  docker run -d -p 3000:3000 --name my-node-app -v $(pwd):/app node:18-alpine npm start
  
  # 5. Run a container with environment variables
  docker run -d --name my-api -e API_KEY=abc123xyz -p 5000:5000 my-api-image:latest
  
  # 6. Run a container and connect to a custom network
  docker run -d --name my-backend --network my-custom-network my-backend-image:latest
  
  # 7. Run a container with a restart policy
  docker run -d --restart always --name my-always-on-app my-app-image:latest

12. docker rm 🗑️ – Removing Containers

This command removes one or more stopped containers.

• Syntax: docker rm [OPTIONS] CONTAINER [CONTAINER...]

• Key Options:

  • --force, -f: 💥 Force the removal of a running container (sends SIGKILL). Use with caution!
  • --volumes, -v: 💾 Remove anonymous volumes associated with the container.

• Usage Examples:

  # 1. Remove a single stopped container
  docker rm my-old-container
  
  # 2. Remove multiple stopped containers
  docker rm container1 container2
  
  # 3. Force remove a running container (not recommended unless absolutely necessary)
  docker rm -f my-stuck-container
  
  # 4. Remove a container and its associated anonymous volumes
  docker rm -v my-temp-container
  
  # 5. Remove all exited containers (useful for cleanup)
  docker rm $(docker ps -a -q -f status=exited)

13. docker rmi 🗑️ – Removing Images

This command removes one or more Docker images.

• Syntax: docker rmi [OPTIONS] IMAGE [IMAGE...]

• Key Options:

  • --force, -f: 💥 Force the removal of an image, even if it’s used by a container. Use with caution!
  • --no-prune: 🌳 Do not delete untagged parent images.

• Usage Examples:

  # 1. Remove an image by name and tag
  docker rmi my-app:latest
  
  # 2. Remove an image by ID
  docker rmi a1b2c3d4e5f6
  
  # 3. Force remove an image that is currently in use by a container (be careful!)
  docker rmi -f old-image:v1
  
  # 4. Remove all dangling images (untagged images not used by any container)
  docker rmi $(docker images -q -f "dangling=true")

14. docker stop / docker start / docker restart 🛑🟢🔄 – Managing Container State

These commands control the lifecycle of your containers.

• Syntax:

  • docker stop [OPTIONS] CONTAINER [CONTAINER...]
  • docker start [OPTIONS] CONTAINER [CONTAINER...]
  • docker restart [OPTIONS] CONTAINER [CONTAINER...]

• Key Options (for stop and restart):

  • --time, `-t `: ⏳ Seconds to wait for stop before killing the container (default is 10 seconds).

• Usage Examples:

  # 1. Stop a running container
  docker stop my-web-app
  
  # 2. Start a stopped container
  docker start my-web-app
  
  # 3. Restart a running container
  docker restart my-web-app
  
  # 4. Stop a container, waiting only 3 seconds before killing
  docker stop -t 3 my-slow-container
  
  # 5. Stop all running containers
  docker stop $(docker ps -q)

15. docker system 🧹📊 – Managing Docker System Resources

This command group provides utilities for managing your Docker installation and its resources.

• Syntax: docker system COMMAND [OPTIONS]

• Common Subcommands:

  • df: 📊 Show Docker disk usage.
  • info: ℹ️ Display system-wide information.
  • prune: 🧹 Remove unused Docker data (containers, images, volumes, networks).

• Key Options (for prune):

  • --all, -a: 💥 Remove all unused images not just dangling ones.
  • --volumes: 💾 Remove all unused volumes.

• Usage Examples:

  # 1. Show disk space used by Docker images, containers, and volumes
  docker system df
  
  # 2. Display detailed Docker system information
  docker system info
  
  # 3. Clean up unused containers, networks, and dangling images (prompt for confirmation)
  docker system prune
  
  # 4. Clean up all unused containers, networks, *all* unused images, and volumes (be careful!)
  docker system prune -a --volumes

16. docker volume 💾 – Managing Data Volumes

The docker volume command manages Docker volumes, which are the preferred mechanism for persisting data generated by and used by Docker containers.

• Syntax: docker volume COMMAND [OPTIONS]

• Common Subcommands:

  • ls: List volumes.
  • create: Create a new volume.
  • inspect: Display detailed information about a volume.
  • rm: Remove one or more volumes.
  • prune: Remove all unused volumes.

• Key Options (for create):

  • `–name `: 📛 Specify a name for the volume.

• Usage Examples:

  # 1. List all local volumes
  docker volume ls
  
  # 2. Create a named volume
  docker volume create my-app-data
  
  # 3. Inspect a specific volume
  docker volume inspect my-app-data
  
  # 4. Remove an unused volume
  docker volume rm my-old-data-volume
  
  # 5. Remove all unused local volumes
  docker volume prune

💡 Beyond the Basics: Pro Tips!

• Aliasing Docker: For frequently used commands, consider creating shell aliases. For example, add alias d='docker' to your ~/.bashrc or ~/.zshrc to shorten commands. Then you can use d ps, d run, etc.
• docker compose: While this guide focuses on individual docker commands, for multi-container applications, docker compose is indispensable. It allows you to define and run a multi-container Docker application using a YAML file. Learn it next!
• .dockerignore: As mentioned earlier, use this file to exclude files and directories from the build context, making your builds faster and images smaller.
• Official Documentation: The Docker official documentation is an excellent, up-to-date resource for every command and option: https://docs.docker.com/engine/reference/commandline/cli/

🎉 Conclusion

You’ve now taken a comprehensive tour of the most critical Docker CLI commands! From building and running containers to managing networks, volumes, and cleaning up your system, these commands are the building blocks of efficient Docker workflows.

Practice these commands regularly, experiment with their options, and soon you’ll find yourself navigating the Docker ecosystem with confidence and speed. Happy containerizing! 🧑‍💻✨