# Essential Docker Commands In this blog post, I wanted to share a high-level overview of Docker and list some of its basic CLI commands and their usage. ## What is Docker? Docker is an open-source platform that automates the deployment of applications inside lightweight, portable containers. Containers are isolated environments that package an application and its dependencies, ensuring consistency across different environments. ## List of Useful Docker Commands: ### 1\. **docker pull** * **Usage**: `docker pull ` * **Description**: This command fetches a Docker image from a registry like Docker Hub. Images serve as templates for containers, making this the initial step to container creation. * **Example**: `docker pull ubuntu:latest` ### 2\. **docker run** * **Usage**: `docker run [options] ` * **Description**: The **docker run** command is fundamental to creating and running containers. It allows you to customize various aspects of the container's behavior using options. Below are some commonly used options: * `-d, --detach`: Run the container in the background, detaching it from your terminal. * `--name `: Assign a custom name to the container, making it easier to manage. * `-p :`: Map a port on your host machine to a port inside the container, enabling network communication. * `-v :`: Create a volume by mapping a directory or file on your host to a directory inside the container, allowing data to persist. * `--env `: Set environment variables within the container. * `--network `: Attach the container to a specific network, facilitating communication with other containers. * `--restart `: Define the container's restart policy (e.g., "no", "always", "on-failure"). * `--memory `: Set a memory limit for the container. * `--cpu-shares `: Specify the CPU shares allocated to the container. * `--privileged`: Give the container full access to the host's devices, which can be useful for certain tasks but should be used with caution. * **Example**: * Start a detached container named "web\_app" from the "my\_web\_app\_image" image, mapping host port 8080 to container port 80, and creating a volume to persist data: ```plaintext docker run -d --name web_app -p 8080:80 -v /host/data:/container/data my_web_app_image ``` * Launch a container in the "my\_network" network with a custom environment variable and a memory limit: ```plaintext docker run --network my_network --env MY_VARIABLE=123 --memory 512m my_image ``` ### 3\. **docker ps** * **Usage**: `docker ps [options]` * **Description**: Listing all currently running containers is a breeze with this command. Add the `-a` option to view all containers, including those that have stopped. * **Example**: `docker ps -a` ### 4\. **docker exec** * **Usage**: `docker exec [options] ` * **Description**: To execute a command within a running container, use this command. It comes in handy for running additional processes or accessing the container's shell. * **Example**: `docker exec -it my_container bash` ### 5\. **docker stop** * **Usage**: `docker stop ` * **Description**: This command gracefully stops a running container by sending a termination signal to its main process. * **Example**: `docker stop my_container` ### 6\. **docker rm** * **Usage**: `docker rm ` * **Description**: Remove stopped containers with this command. Use the `-f` option to forcefully remove a running container. * **Example**: `docker rm my_container` ### 7\. **docker rmi** * **Usage**: `docker rmi ` * **Description**: Delete a Docker image using this command. Ensure no containers are using the image before attempting removal. * **Example**: `docker rmi ubuntu:latest` ### 8\. **docker build** * **Usage**: `docker build [options] -t ` * **Description**: The **docker build** command is used to build a Docker image from a Dockerfile. It provides several options to fine-tune the build process. Below are some commonly used options: * `-t, --tag `: Assign a name and optional tag to the built image for easier identification. * `--file `: Specify the path to the Dockerfile if it's not named "Dockerfile" or located in a different directory. * `--build-arg `: Pass build-time variables to the Dockerfile. * `--no-cache`: Build the image without using the cache, ensuring a fresh build. * `--pull`: Always attempt to pull a newer version of the base image. * `--squash`: Optimize the resulting image by squashing the layers into a single layer. * `--target `: Build up to a specific build stage in a multi-stage Dockerfile. * `--buildkit`: Enable BuildKit, a modern build subsystem for Docker, to take advantage of advanced features and improved performance. * **Example**: * Build an image named "my\_custom\_image" from the Dockerfile in the current directory and set a build-time variable: ```plaintext docker build -t my_custom_image --build-arg MY_VARIABLE=123 . ``` * Build a Dockerfile located in a different directory and name the resulting image: ```plaintext docker build -t my_other_image --file /path/to/Dockerfile/ my_custom_directory ``` ### 9\. **docker-compose** * **Usage**: `docker-compose [options] ` * **Description**: Manage multi-container Docker applications defined in a YAML file (docker-compose.yml) using this command. It's indispensable for orchestrating complex applications with multiple services. * **Example**: `docker-compose up` ### 10\. **docker logs** * **Usage**: `docker logs [options] ` * **Description**: Display the logs of a running container with this command. It's a valuable tool for debugging and monitoring containerized applications. * **Example**: `docker logs my_container` ### **11\. docker stop all running containers at once (combining commands)** * **Usage**: `docker stop $(docker ps -q)` * **Description**: To stop all running containers at once, use this command. It leverages a subcommand to obtain the list of running container IDs and passes them to the `docker stop` command. * **Example**: `docker stop $(docker ps -q)` I hope to share more of what I've learned in future blog posts.