Removing containers in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of removing a running container

What will be the output or result of running this command if the container myapp is currently running?

docker rm myapp

Docker

docker rm myapp

A Container myapp stopped and removed automatically.

B Container myapp removed successfully.

C Error: You cannot remove a running container. Stop it first.

D Warning: Container myapp is running but removed forcefully.

💡 Hint

Think about whether Docker allows removing containers that are running without extra flags.

Docker does not allow removing a running container with 'docker rm' unless you use the '-f' (force) option. Without it, you get an error telling you to stop the container first.

💻 Command Output

intermediate

Effect of force removing a container

What happens when you run this command?

docker rm -f myapp

Docker

docker rm -f myapp

A The container myapp is stopped if running and then removed.

B The container myapp is removed only if it is stopped.

C The command fails if the container is running.

D The container myapp is paused but not removed.

💡 Hint

The '-f' flag forces removal even if the container is running.

The '-f' or '--force' option stops the container if it is running and then removes it.

❓ Configuration

advanced

Removing all stopped containers

Which command will remove all stopped containers safely without affecting running ones?

A docker rm -a

B docker rm $(docker ps -a -q)

C docker rm -f $(docker ps -q)

D docker container prune

💡 Hint

Look for a command that cleans up stopped containers only.

The command 'docker container prune' removes all stopped containers safely. Option D tries to remove all containers including running ones, causing errors. Option D forcibly removes running containers which is unsafe. Option D is invalid syntax.

❓ Troubleshoot

advanced

Error when removing container by name

You run docker rm myapp but get the error:

Error: No such container: myapp

What is the most likely cause?

A Docker daemon is not running.

B The container named 'myapp' does not exist or is already removed.

C The container is running and cannot be removed.

D You do not have permission to remove containers.

💡 Hint

Check if the container name is correct and exists.

The error means Docker cannot find a container with the name 'myapp'. It may have been removed or the name is misspelled.

✅ Best Practice

expert

Safe workflow to remove containers and free disk space

Which sequence of commands is the safest and most effective to remove all stopped containers and free disk space without affecting running containers or images?

A 1,2,3,4

B 2,1,4,3

C 4,3,2,1

D 1,3,4,2

💡 Hint

Start by removing stopped containers, then images, volumes, and networks.

The best practice is to first remove stopped containers, then unused images, volumes, and networks in that order to safely free space without affecting running containers.