Docker

Docker CLI

Basic Commands

docker --version
- Check Docker version.
```
docker --version
```
docker info
- Display system-wide information.
```
docker info
```
docker help
- Get help on Docker commands.
```
docker help
```

Images

docker images
- List all Docker images.
```
docker images
```
docker pull [image]
- Pull an image from a registry.
```
docker pull ubuntu:latest
```
docker rmi [image_id]
- Remove a Docker image.
```
docker rmi ubuntu:latest
```

Containers

docker ps
- List running containers.
```
docker ps
```
docker ps -a
- List all containers (running and stopped).
```
docker ps -a
```
docker run [options] [image]
- Run a command in a new container.
```
docker run -it ubuntu:latest /bin/bash
```
docker stop [container_id]
- Stop a running container.
```
docker stop [container_id]
```
docker start [container_id]
- Start a stopped container.
```
docker start [container_id]
```
docker restart [container_id]
- Restart a container.
```
docker restart [container_id]
```
docker rm [container_id]
- Remove a stopped container.
```
docker rm [container_id]
```

Networks

docker network ls
- List all networks.
```
docker network ls
```
docker network create [network_name]
- Create a new network.
```
docker network create my_network
```
docker network rm [network_name]
- Remove a network.
```
docker network rm my_network
```

Volumes

docker volume ls
- List all volumes.
```
docker volume ls
```
docker volume create [volume_name]
- Create a new volume.
```
docker volume create my_volume
```
docker volume rm [volume_name]
- Remove a volume.
```
docker volume rm my_volume
```

Docker Compose

docker-compose up
- Create and start containers.
```
docker-compose up
```
docker-compose down
- Stop and remove containers, networks, images, and volumes.
```
docker-compose down
```
docker-compose build
- Build or rebuild services.
```
docker-compose build
```

Inspect and Logs

docker inspect [container_id]
- Return low-level information on Docker objects.
```
docker inspect [container_id]
```
docker logs [container_id]
- Fetch the logs of a container.
```
docker logs [container_id]
```

Clean Up

docker system prune
- Remove all unused containers, networks, images (both dangling and unreferenced), and optionally, volumes.
```
docker system prune
```
docker container prune
- Remove all stopped containers.
```
docker container prune
```
docker volume prune
- Remove all unused volumes.
```
docker volume prune
```
docker image prune
- Remove unused images.
```
docker image prune
```

This cheat sheet covers the basic and most commonly used Docker commands to get you started. Feel free to ask if you need more details or advanced commands!

Creating a Dockerfile

A Dockerfile is a text file that contains a series of instructions on how to build a Docker image. Here's a basic overview and examples of common Dockerfile instructions:

Basic Structure of a Dockerfile

FROM
- Specifies the base image.
```
FROM ubuntu:latest
```
MAINTAINER
- Sets the author field of the generated images.
```
MAINTAINER Your Name <your.email@example.com>
```
RUN
- Executes commands in a new layer on top of the current image.
```
RUN apt-get update && apt-get install -y nginx
```
COPY
- Copies files from the host machine to the Docker image.
```
COPY ./localfile /path/in/container
```
ADD
- Copies files/directories from the host machine to the Docker image, and also supports extracting tar files.
```
ADD ./localfile.tar /path/in/container
```
CMD
- Specifies the command to run within the container.
```
CMD ["nginx", "-g", "daemon off;"]
```
ENTRYPOINT
- Sets a default application to be used every time a container is created with the image.
```
ENTRYPOINT ["nginx", "-g", "daemon off;"]
```
EXPOSE
- Informs Docker that the container listens on the specified network ports at runtime.
```
EXPOSE 80
```
ENV
- Sets environment variables.
```
ENV ENVIRONMENT production
```
VOLUME
- Creates a mount point with the specified path and marks it as holding externally mounted volumes from the native host or other containers.
```
VOLUME /data
```

Example Dockerfile

Here's an example Dockerfile for a simple web server using Nginx:

# Use the official Nginx image from the Docker Hub
FROM nginx:latest

# Set the maintainer label
MAINTAINER Your Name <your.email@example.com>

# Copy custom configuration file from the host to the container
COPY nginx.conf /etc/nginx/nginx.conf

# Copy the content of the website to the container
COPY ./html /usr/share/nginx/html

# Expose port 80 to the host
EXPOSE 80

# Start Nginx when the container launches
CMD ["nginx", "-g", "daemon off;"]

Building and Running the Docker Image

Build the Docker Image
- Use the docker build command to create an image from the Dockerfile.
```
docker build -t my-nginx-image .
```
Run the Docker Container
- Use the docker run command to start a container from the image.
```
docker run -d -p 80:80 my-nginx-image
```

Best Practices

Keep Dockerfile Instructions Ordered: Use a logical order such as FROM, MAINTAINER, RUN, COPY, CMD.
Use .dockerignore: Create a .dockerignore file to exclude files and directories from the build context to reduce the size of the image.
Minimize Layers: Combine multiple RUN commands to reduce the number of layers.
Leverage Caching: Order the instructions to leverage Docker’s build cache.

This should give you a good starting point for creating your own Dockerfiles! If you have any specific questions or need further details, feel free to ask.

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Last updated 9 months ago

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