Lesson 5: Managing Container Lifecycles

In real-world scenarios, we need containers to run continuously in the background. This requires managing their state: starting, stopping, pausing, and removing.

Running Containers in Detached Mode

To run a container in the background (detached mode), we use the -d flag. Let's run a lightweight Nginx web server:

bash docker run -d --name my_web_server -p 8080:80 nginx

Breakdown:

• -d: Detached mode (runs in the background).
• --name my_web_server: Assigns a readable name instead of a random ID.
• -p 8080:80: Port Mapping. Maps port 80 inside the container to port 8080 on our host machine.
• nginx: The image to use.

Now, check the running container:

bash docker ps

You should see my_web_server listed, showing its status as Up and the port mapping 0.0.0.0:8080->80/tcp.

You can now access the Nginx welcome page by navigating to http://localhost:8080 in your web browser.

Stopping and Starting Containers

Containers can be managed using their assigned name or ID.

1. Stopping

bash docker stop my_web_server

Check docker ps again; the container should be gone from the running list, but it still exists (check docker ps -a).

2. Starting

bash docker start my_web_server

3. Restarting

bash docker restart my_web_server

Removing Containers

To permanently delete a stopped container, use docker rm.

bash docker rm my_web_server

Tip: To remove all stopped containers efficiently, you can use:

bash docker container prune