Docker Basics Cheat Sheet

1. Core Concepts

• Docker: A platform to develop, ship, and run applications in isolated containers.

• Container: A lightweight, portable package that includes an application and its dependencies, ensuring consistent performance regardless of the environment.

• Image: A read-only template used to create containers. Images are built from a series of instructions in a Dockerfile.

• Dockerfile: A file with a list of instructions on how to build a Docker image.

• Registry: A repository to store Docker images (e.g., Docker Hub, Google Container Registry).

• Volume: A method to persist data generated by Docker containers outside of the container’s file system.

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2. Basic Commands

Docker Installation & Setup

• Install Docker on your OS by following the official Docker installation guide.

• Start Docker service:

    bashCopy codesudo systemctl start docker
  

Docker Version and Info

• Check Docker version:

    bashCopy codedocker --version
  

• Display detailed Docker information:

    bashCopy codedocker info
  

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3. Working with Images

Search and Pull an Image

• Search for images on Docker Hub:

    bashCopy codedocker search <image-name>
  

• Download (pull) an image:

    bashCopy codedocker pull <image-name>:<tag>
  

  Example: docker pull nginx:latest

List Images

• List all downloaded images:

    bashCopy codedocker images
  

Remove an Image

• Delete an image:

    bashCopy codedocker rmi <image-id>
  

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4. Running Containers

Start a Container

• Run a container from an image:

    bashCopy codedocker run <image-name>
  

• Run in detached mode (in the background):

    bashCopy codedocker run -d <image-name>
  

• Run with a custom name:

    bashCopy codedocker run --name <container-name> <image-name>
  

• Expose container port to host:

    bashCopy codedocker run -p <host-port>:<container-port> <image-name>
  

List and Stop Containers

• List all running containers:

    bashCopy codedocker ps
  

• List all containers (including stopped):

    bashCopy codedocker ps -a
  

• Stop a running container:

    bashCopy codedocker stop <container-id>
  

• Start a stopped container:

    bashCopy codedocker start <container-id>
  

Remove Containers

• Remove a specific container:

    bashCopy codedocker rm <container-id>
  

• Remove all stopped containers:

    bashCopy codedocker container prune
  

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5. Managing Volumes

Creating and Using Volumes

• Create a volume:

    bashCopy codedocker volume create <volume-name>
  

• Mount a volume when running a container:

    bashCopy codedocker run -v <volume-name>:<container-path> <image-name>
  

• List all volumes:

    bashCopy codedocker volume ls
  

• Inspect a volume:

    bashCopy codedocker volume inspect <volume-name>
  

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6. Building Images with Dockerfile

Dockerfile Commands

• FROM: Sets the base image (e.g., FROM ubuntu:latest).

• COPY: Copies files/directories from the host to the container.

• RUN: Executes commands in the container (e.g., RUN apt-get update).

• CMD: Sets default command for the container (e.g., CMD ["nginx"]).

• EXPOSE: Informs Docker the container will listen on a specified port.

• ENV: Sets environment variables.

Build an Image from Dockerfile

• Build command:

    bashCopy codedocker build -t <image-name>:<tag> <path-to-dockerfile-directory>
  

  Example: docker build -t myapp:latest .

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7. Docker Networks

• List Docker networks:

    bashCopy codedocker network ls
  

• Create a network:

    bashCopy codedocker network create <network-name>
  

• Attach a container to a network:

    bashCopy codedocker network connect <network-name> <container-name>
  

• Disconnect a container from a network:

    bashCopy codedocker network disconnect <network-name> <container-name>
  

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8. Docker Compose

• Docker Compose: A tool for defining and running multi-container Docker applications using a docker-compose.yml file.

Basic Commands for Docker Compose

• Start all services defined in docker-compose.yml:

    bashCopy codedocker-compose up
  

• Start in detached mode:

    bashCopy codedocker-compose up -d
  

• Stop all services:

    bashCopy codedocker-compose down
  

• View logs:

    bashCopy codedocker-compose logs
  

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9. Docker Logs and Debugging

Viewing Logs

• See logs of a container:

    bashCopy codedocker logs <container-id>
  

• Follow logs in real-time:

    bashCopy codedocker logs -f <container-id>
  

Execute Commands in a Running Container

• Access the terminal of a running container:

    bashCopy codedocker exec -it <container-id> /bin/bash
  

• Run a command inside a running container:

    bashCopy codedocker exec <container-id> <command>
  

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10. Docker Best Practices

• Use .dockerignore: Exclude files/folders from the image to reduce size.

• Optimize Dockerfile layers: Combine RUN commands when possible.

• Use specific tags: Avoid using latest tag in production environments.

• Clean up unused images and containers:

    bashCopy codedocker system prune
  

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This cheat sheet should help you with the basics of Docker, from setting up and managing containers to building images and using Docker Compose. For more advanced commands and configurations, refer to the official Docker documentation.