Container Lifecycle

Running a container

docker run is the most common command you will use. It pulls the image if needed, creates a container, and starts it.

docker run nginx:alpine

This runs nginx in the foreground — your terminal attaches to its output. Press Ctrl+C to stop it.

Detached mode with -d

Add -d to run the container in the background:

docker run -d nginx:alpine

Docker prints the full container ID and returns your prompt immediately.

Naming a container with --name

By default Docker assigns a random name. Use --name to give it a predictable one:

docker run -d --name webserver nginx:alpine

Listing containers

# Only running containers
docker ps

# All containers — running AND stopped
docker ps -a

CONTAINER ID   IMAGE          STATUS                     NAMES
a1b2c3d4e5f6   nginx:alpine   Up 2 minutes               webserver
b7c8d9e0f1a2   alpine         Exited (0) 5 minutes ago   old-task

The STATUS column tells you whether the container is running (Up) or stopped (Exited).

Stopping, starting, and restarting

# Graceful stop — sends SIGTERM, waits 10 s, then SIGKILL
docker stop webserver

# Start a stopped container
docker start webserver

# Restart (stop then start)
docker restart webserver

docker stop does not remove the container. It remains on disk in the stopped state.

Removing a container

# Remove a stopped container
docker rm webserver

# Force-remove a running container (sends SIGKILL)
docker rm -f webserver

You cannot remove a running container without -f.

Auto-cleanup with --rm

For one-shot tasks you never want to manage manually, add --rm. The container is removed automatically the moment its process exits.

docker run --rm alpine echo "Hello, Docker!"

Hello, Docker!

The container is gone as soon as the echo finishes — no docker rm needed.

# 1. Run nginx detached with a name
docker run -d --name webserver nginx:alpine

# 2. List running containers
docker ps

# 3. Stop it
docker stop webserver

# 4. Show all containers — notice STATUS is Exited
docker ps -a

# 5. Start it again
docker start webserver

# 6. Remove it (stop first)
docker stop webserver && docker rm webserver

# 7. One-shot: auto-cleanup with --rm
docker run --rm alpine echo "done — already gone"

Explore the container lifecycle ↗

🐳 Stopped containers still exist until removed

docker stop pauses the container — it does not delete it. Stopped containers accumulate on disk (each holds a writable layer). Use docker rm when you are done, or pass --rm at run time so Docker removes the container automatically on exit.

What does 'docker stop' send to the container's main process first?

SIGKILL SIGTERM SIGINT SIGHUP

Which command shows ALL containers, including stopped ones?

docker ps docker ps --running docker ps -a docker container list

What does the --rm flag do?

Removes the image after the container exits Removes the container automatically when its process exits Forces the container to restart on failure Removes all stopped containers before running a new one

Can you remove a running container without the -f flag?

Yes — docker rm always works Yes — but only if the container was started with --rm No — you must stop it first or use docker rm -f No — running containers can never be removed

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