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aykhlf yassir
aykhlf yassir

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Everyday Docker CLI

#beginners #cli #docker #tutorial

Docker has a massive surface area, but your day-to-day workflow only relies on a handful of commands. here is the essential cheat sheet for running, debugging, and cleaning up.

1. Running Containers (docker run)

The docker run command is your workhorse. By combining a few key flags, you can control exactly how your container behaves.

Run in the background with a specific name:

docker run -d --name my-cache redis:7-alpine
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  • -d runs the container in detached mode (background).
  • --name gives it a recognizable name instead of a random hash.

Expose ports securely (Localhost only):

docker run -p 127.0.0.1:8080:80 nginx:alpine
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  • Maps port 80 inside the container to port 8080 on your host machine, restricting access strictly to your local loopback address.

Inject Environment Variables:

# Single variable
docker run -e ENV=prod python:3.12-slim

# From a file
docker run --env-file .env python:3.12-slim
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Auto-cleanup for one-off tasks:

docker run --rm python:3.12-slim python -c "print('Done!')"
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  • --rm ensures the container is automatically deleted from your system the moment it stops running.

2. Debugging and Interacting

Once a container is running, you need visibility into what it's doing.

Stream live logs:

docker logs -f my-cache
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  • The -f (follow) flag streams the logs in real-time. Use Ctrl+C to exit.

Drop into a shell of an already running container:

docker exec -it my-cache sh
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  • Unlike docker run (which creates a new container), exec opens an interactive (-it) shell inside an existing one.

3. Container Lifecycle

Knowing how to stop a container properly prevents data corruption and hanging processes.

Graceful shutdown:

docker stop my-cache
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  • Sends a SIGTERM signal, giving the container time to save state and shut down cleanly.

Force shutdown (when frozen):

docker kill my-cache
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  • Sends an immediate SIGKILL signal. Use this only when stop fails.

4. Visibility and Cleanup

Docker accumulates stopped containers and unused images fast. Keep your system clean.

List all containers (including stopped ones):

docker ps -a
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Safe system cleanup:

docker system prune
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  • Removes stopped containers, unused networks, and "dangling" (untagged/unnamed) images.

Aggressive system cleanup:

docker system prune -a
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  • Use with caution: This wipes everything that isn't currently attached to a container, including your standard tagged images (like nginx:alpine). You will have to re-download them from Docker Hub the next time you need them.

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