Docker Quick Commands Cheat Sheet

This guide provides a quick reference for the most common commands used in the Docker and Docker Compose workflows.

Managing Containers (Lifecycle)

Command	Description
`docker run [OPTIONS] IMAGE [COMMAND]`	Creates and starts a new container from an image.
`docker ps`	Lists all running containers.
`docker ps -a`	Lists all containers, including stopped ones.
`docker start <container_id_or_name>`	Starts one or more stopped containers.
`docker stop <container_id_or_name>`	Stops one or more running containers gracefully.
`docker kill <container_id_or_name>`	Forcibly stops one or more running containers.
`docker rm <container_id_or_name>`	Removes one or more stopped containers.
`docker rm -f <container_id_or_name>`	Forcibly removes a container (even if it's running).
`docker prune containers`	Removes all stopped containers.

Common docker run Flags

Flag	Description
`-d`	Detached mode: runs the container in the background.
`-it`	Interactive mode: connects your terminal to the container's terminal.
`--rm`	Automatically removes the container when it exits.
`-p <host_port>:<container_port>`	Maps a port on the host to a port in the container.
`--name <my_container_name>`	Assigns a custom name to the container.
`-v <host_path>:<container_path>`	Mounts a host directory or volume into the container.
`-w /path/to/workdir`	Sets the working directory inside the container.
`--network <network_name>`	Connects the container to a specific network.

Inspecting and Debugging

Command	Description
`docker logs <container_id_or_name>`	Fetches the logs of a container.
`docker logs -f <container_id_or_name>`	Follows the log output in real-time.
`docker exec -it <container_id_or_name> bash`	Executes a command (like `bash`) inside a running container.
`docker inspect <container_id_or_name>`	Displays low-level information on Docker objects.

Managing Images

Command	Description
`docker images` or `docker image ls`	Lists all images on the local machine.
`docker pull <image_name>:<tag>`	Downloads an image from a registry (like Docker Hub).
`docker build -t <tag_name> .`	Builds an image from a Dockerfile in the current directory.
`docker rmi <image_id_or_name>`	Removes one or more images.
`docker login` / `docker logout`	Logs in to or out of a container registry.
`docker push <username>/<image_name>:<tag>`	Uploads an image to a container registry.

Building Images (Dockerfile)

A Dockerfile is a text file with instructions for building a Docker image.

Example myprog.py:

print("Hello from my Docker container!")

Example Dockerfile:

# Start from an official base image
FROM python:3.9-slim

# Set the working directory inside the container
WORKDIR /app

# Copy the application code into the container
COPY myprog.py .

# Define the command to run when the container starts
CMD ["python", "myprog.py"]

Build Command:

# Build the image and tag it as 'my-python-app'
docker build -t my-python-app .

Run Command:

docker run --rm my-python-app

Managing Multi-Container Applications (Docker Compose)

Docker Compose is a tool for defining and running multi-container applications using a YAML file.

Example docker-compose.yml: This file builds the image from the Dockerfile above and mounts the current directory into the container's /app directory, allowing for live code changes without rebuilding.

version: "3.8"

services:
  my_app:
    build: .
    volumes:
      - ./:/app

Common Docker Compose Commands

Command	Description
`docker-compose up`	Creates and starts containers defined in the YAML file.
`docker-compose up -d`	Creates and starts containers in detached mode.
`docker-compose down`	Stops and removes containers, networks, and volumes.
`docker-compose ps`	Lists the containers for the current project.
`docker-compose logs`	Displays logs from the services.
`docker-compose exec <service_name> bash`	Executes a command in a running service.
`docker-compose build`	Builds or rebuilds the images for the services.