# Docker ## Docker CLI ### Basic Commands * **docker --version** * Check Docker version. ```sh docker --version ``` * **docker info** * Display system-wide information. ```sh docker info ``` * **docker help** * Get help on Docker commands. ```sh docker help ``` ### Images * **docker images** * List all Docker images. ```sh docker images ``` * **docker pull \[image]** * Pull an image from a registry. ```sh docker pull ubuntu:latest ``` * **docker rmi \[image\_id]** * Remove a Docker image. ```sh docker rmi ubuntu:latest ``` ### Containers * **docker ps** * List running containers. ```sh docker ps ``` * **docker ps -a** * List all containers (running and stopped). ```sh docker ps -a ``` * **docker run \[options] \[image]** * Run a command in a new container. ```sh docker run -it ubuntu:latest /bin/bash ``` * **docker stop \[container\_id]** * Stop a running container. ```sh docker stop [container_id] ``` * **docker start \[container\_id]** * Start a stopped container. ```sh docker start [container_id] ``` * **docker restart \[container\_id]** * Restart a container. ```sh docker restart [container_id] ``` * **docker rm \[container\_id]** * Remove a stopped container. ```sh docker rm [container_id] ``` ### Networks * **docker network ls** * List all networks. ```sh docker network ls ``` * **docker network create \[network\_name]** * Create a new network. ```sh docker network create my_network ``` * **docker network rm \[network\_name]** * Remove a network. ```sh docker network rm my_network ``` ### Volumes * **docker volume ls** * List all volumes. ```sh docker volume ls ``` * **docker volume create \[volume\_name]** * Create a new volume. ```sh docker volume create my_volume ``` * **docker volume rm \[volume\_name]** * Remove a volume. ```sh docker volume rm my_volume ``` ### Docker Compose * **docker-compose up** * Create and start containers. ```sh docker-compose up ``` * **docker-compose down** * Stop and remove containers, networks, images, and volumes. ```sh docker-compose down ``` * **docker-compose build** * Build or rebuild services. ```sh docker-compose build ``` ### Inspect and Logs * **docker inspect \[container\_id]** * Return low-level information on Docker objects. ```sh docker inspect [container_id] ``` * **docker logs \[container\_id]** * Fetch the logs of a container. ```sh docker logs [container_id] ``` ### Clean Up * **docker system prune** * Remove all unused containers, networks, images (both dangling and unreferenced), and optionally, volumes. ```sh docker system prune ``` * **docker container prune** * Remove all stopped containers. ```sh docker container prune ``` * **docker volume prune** * Remove all unused volumes. ```sh docker volume prune ``` * **docker image prune** * Remove unused images. ```sh 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 1. **FROM** * Specifies the base image. ```Dockerfile FROM ubuntu:latest ``` 2. **MAINTAINER** * Sets the author field of the generated images. ```Dockerfile MAINTAINER Your Name ``` 3. **RUN** * Executes commands in a new layer on top of the current image. ```Dockerfile RUN apt-get update && apt-get install -y nginx ``` 4. **COPY** * Copies files from the host machine to the Docker image. ```Dockerfile COPY ./localfile /path/in/container ``` 5. **ADD** * Copies files/directories from the host machine to the Docker image, and also supports extracting tar files. ```Dockerfile ADD ./localfile.tar /path/in/container ``` 6. **CMD** * Specifies the command to run within the container. ```Dockerfile CMD ["nginx", "-g", "daemon off;"] ``` 7. **ENTRYPOINT** * Sets a default application to be used every time a container is created with the image. ```Dockerfile ENTRYPOINT ["nginx", "-g", "daemon off;"] ``` 8. **EXPOSE** * Informs Docker that the container listens on the specified network ports at runtime. ```Dockerfile EXPOSE 80 ``` 9. **ENV** * Sets environment variables. ```Dockerfile ENV ENVIRONMENT production ``` 10. **VOLUME** * Creates a mount point with the specified path and marks it as holding externally mounted volumes from the native host or other containers. ```Dockerfile VOLUME /data ``` ### Example Dockerfile Here's an example Dockerfile for a simple web server using Nginx: ```Dockerfile # Use the official Nginx image from the Docker Hub FROM nginx:latest # Set the maintainer label MAINTAINER Your Name # 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 1. **Build the Docker Image** * Use the `docker build` command to create an image from the Dockerfile. ```sh docker build -t my-nginx-image . ``` 2. **Run the Docker Container** * Use the `docker run` command to start a container from the image. ```sh 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. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.hackerspot.net/cheatsheets/cloud-tools/docker.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.