Docker Cheat Sheet: Commands and Concepts

This guide covers essential Docker commands, from creating containers, managing images, building Dockerfiles, to working with volumes.

🚀 Creating and Running Containers

1. Run a Container from an Image

To create and run a container from an image:

docker run image

2. Run a Container in Interactive Mode

To run a container and open its terminal:

docker run -it image
  • After the container starts, you can interact with it directly in the terminal.

3. Name a Container

To give a container a specific name:

docker run --name container_name image

4. Port Mapping

To map a port from your computer to the container:

docker run -p computer_port:container_port image
  • Incoming traffic to computer_port will be forwarded to container_port in the container.

5. Run a Container in the Background (Detached Mode)

To run the container in the background:

docker run -d image

6. Passing Environment Variables to a Container

To pass environment variables to a container:

docker run -e key=value image

🛠️ Managing Containers

7. Start a Container

To start an existing container:

docker start container_id

8. Stop a Container

To stop a running container:

docker stop container_id

9. Remove a Container

To remove a container:

docker rm container_id
  • Note: The container must be stopped before removal.

10. Execute a Command in a Running Container

To start a terminal session inside a running container:

docker exec -it container_id bash

11. View Running Containers

To list all currently running containers:

docker ps

12. View All Containers (Running and Stopped)

To see all containers, including those that are stopped:

docker ps -a

🧱 Building Docker Images

13. Creating a Dockerfile

A Dockerfile is a script used to build Docker images. Here’s an example of common Dockerfile commands:

# Set the base image for your container
FROM base_image

# Run commands during the image build process
RUN command

# Copy files from your local machine to the container
COPY source /path/in/container

# Set environment variables
ENV key=value

# Expose a port for the container
EXPOSE 8080

# Define the command to run when the container starts
CMD ["executable"]

# Optionally, run commands automatically when the container starts
ENTRYPOINT ["/path/to/script"]

# Set the working directory in the container
WORKDIR /app

# Copy all files from the local directory to the container, excluding files listed in .dockerignore
COPY . .

14. Building a Docker Image

To build a Docker image from a Dockerfile:

docker build -t image_name /path/to/Dockerfile

📂 Managing Docker Files

15. Using the .dockerignore File

The .dockerignore file helps exclude unnecessary files from being copied into the Docker image, improving build speed and reducing image size:

node_modules/
.git/

16. COPY Command in Dockerfile

The COPY command copies files from your local system to the container:

  • Copy all files from the current directory to the container:
COPY . /path/in/container
  • Copy a specific file:
COPY ./filename.extension /path/in/container
  • Copy an entire folder:
COPY ./foldername /path/in/container
  • Copy contents of a folder (not the folder itself):
COPY ./foldername/ /path/in/container

📦 Working with Volumes

17. Mounting Volumes

Volumes allow data to persist even if the container is deleted. To mount a folder from your host to the container:

docker run -it -v /path/on/host:/path/in/container image
  • Example:
docker run -it -v /home/user/backup:/app/data ubuntu
  • This will map /home/user/backup on your host to /app/data inside the container.

Use Cases for Volumes:

  1. Data Persistence: Preserve data even after the container is removed.
  2. Backups: Easily back up container data to the host.
  3. Shared Data: Share data between multiple containers or between host and container.

💾 Publishing Docker Images

18. Pushing an Image to Docker Hub

To publish an image to Docker Hub:

  1. Tag the image with your Docker Hub username:
docker tag image_name username/image_name
  1. Log in to Docker Hub:
docker login
  1. Push the image to your repository:
docker push username/image_name

This guide gives you the essentials for working with Docker. With these commands, you’ll be able to manage containers, build images, use volumes, and more effectively.