Running Containers

Running Docker Containers Cheat Sheet

Overview

Once you've built or pulled a Docker image, you can run it in a container. Containers are lightweight, portable environments that isolate your application. Below are the essential commands and options for running, managing, and interacting with containers.

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Running a Container

Command	Description
docker run <image>:<tag>	Run a container from the specified image. If no tag is specified, latest is used by default.
docker run --name <container_name> <image>:<tag>	Assign a custom name to the container.
docker run -d <image>:<tag>	Run the container in detached mode (in the background).
docker run -it <image>:<tag>	Run the container interactively, useful for debugging or terminal-based applications.
docker run -p <host_port>:<container_port> <image>:<tag>	Map a container's port to the host system (e.g., -p 8080:80).
docker run -v <host_path>:<container_path> <image>:<tag>	Mount a volume to persist data or share files between the host and the container.
docker run --env <key>=<value> <image>:<tag>	Pass environment variables to the container.

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Starting and Stopping Containers

Command	Description
docker start <container_name>	Start a stopped container.
docker stop <container_name>	Stop a running container.
docker restart <container_name>	Restart a running container.
docker pause <container_name>	Pause all processes in a container.
docker unpause <container_name>	Resume a paused container.
docker rm <container_name>	Remove a stopped container.

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Listing Containers

Command	Description
docker ps	List all running containers.
docker ps -a	List all containers, including stopped ones.
docker ps -q	List only the container IDs of running containers.

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Accessing a Running Container

Command	Description
docker exec -it <container_name> <command>	Run a command inside a running container (e.g., bash, sh, or other commands).
docker logs <container_name>	View the logs of a container.
docker attach <container_name>	Attach to a running container’s standard input, output, and error streams.
docker cp <container_name>:<container_path> <host_path>	Copy files from a container to the host system.
docker cp <host_path> <container_name>:<container_path>	Copy files from the host to a container.

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Example: Running a Web Server

To run an Nginx web server container:

1. Pull the Nginx image:

   docker pull nginx:latest

2. Run the container and expose port 8080:

   docker run -d -p 8080:80 --name my-nginx nginx:latest

3. Access the web server at http://localhost:8080.

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Removing Containers

Command	Description
docker rm <container_name>	Remove a stopped container.
docker rm -f <container_name>	Force remove a running container.
docker container prune	Remove all stopped containers to clean up unused resources.

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Inspecting Containers

Command	Description
docker inspect <container_name>	View detailed information about a container.
docker stats <container_name>	Display real-time resource usage statistics of a container.

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Managing Container Lifecycle

Command	Description
docker update <container_name> --memory <value>	Update resource limits (e.g., memory, CPU) for a running container.
docker commit <container_name> <new_image>:<tag>	Create a new image from a container’s current state.

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Best Practices for Running Containers

1. Use Named Containers: Assign meaningful names to containers using the --name flag for easier management.
2. Avoid Exposing All Ports: Only expose the ports that are needed, and restrict access using firewalls.
3. Use Volumes: Persist important data using Docker volumes instead of relying on the container's filesystem.
4. Resource Constraints: Limit CPU and memory usage using --memory and --cpus flags to prevent resource exhaustion.