Docker rm

Introduction to Docker rm

The ‘docker rm’ command is used to remove or delete Docker containers. It can be used to delete a single container or multiple containers using a single command, but the container must be in a stopped state unless we want to delete the containers forcefully using the ‘-f’ option. This command requires ‘container ID’ or ‘container name’ to be passed to remove or delete the container. It deletes all the data stored inside the container, and there is no way to get it back, so we use persistent storage to store the data to preserve it.

Syntax:

docker rm [OPTIONS] CONTAINER [CONTAINER...]

Options:

• -f, –force: It is used to remove the running container forcefully using the ‘SIGKILL’ signal.
• -l, –link: It is used to remove a specified link that exists.
• -v, –volume: It also removes the volumes attached with the container.

We can use the ‘–help’ option to get help at any time.

Code:

docker rm --help

Output:

How does rm Command work in Docker?

• First, Docker CLI must be installed on the host to run the docker commands.
• When we run the ‘docker rm’ command, the Docker client makes an API call to the Docker daemon, and then Docker daemon searches for the containers mentioned in the command, and once it finds the container, then it checks the status of the container, and if the container is running then it throws the error that the container is running and suggests us to either stop the container before removing the same or force remove and if the container is not running then it simply removes the container and output the container ID or name whatever we pass using the command line.
• We have to the ‘-f’ flag to forcefully remove the container.

Examples of Docker rm

Given below are the examples of Docker rm:

Example #1

Remove one or more containers.

Step 1: Create three containers; one should be in the exited state, and the other two must be in running state as below:

Code:

docker run -d ubuntu
docker run -d nginx
docker run -d nginx

Output:

Step 2: Let’s try to delete all the containers at once as below:

Code:

docker rm gallant_volhard brave_borg reverent_bell

Output:

Explanation:

• In the above snapshot, we can see that the only exited container got deleted. However, the other two running containers did not get deleted. Therefore, we can see that those containers are still running in the below snapshot.

Code:

docker ps -a

Output:

We have now two ways to get rid of these containers, either we stop the container first and then delete it or use the ‘-f’ flag to remove the container forcefully.

Step 3: Let’s stop the ‘gallant_volhard’ container and delete it as below:

Code:

docker stop gallant_volhard && docker rm gallant_volhard

Output:

We got the container name two times because we have used two commands at the same, the one is to stop the container and the second one is to remove it.

Step 4: Let’s forcefully remove the container using the ‘-f’ flag as below:

Code:

docker rm -f brave_borg

Output:

Example #2

Remove linked containers and links.

Step 1: Let’s create a linked container using below the commands:

Code:

docker run -d --name my-db mysql sleep 3600
docker run -d -P --name my-web --link my-db:db nginx

Output:

Step 2: Delete the containers running under link /my-web and /my-db as shown below:

Code:

docker rm -f /my-web
docker rm -f /my-db

Output:

Explanation:

•  In the above snapshot, we can see that we have to the ‘-f’ flag as it is going to remove the container, and if we don’t use that flag, then it will throw an error that the running container cannot be removed.

Step 3: We can only delete the link between the containers as well using the below command:

Code:

docker rm -l /my-web/db

Output:

Explanation:

• In the above snapshot, we recreate the linked containers and checked that link using the ‘inspect’ command. After that, we removed the link using the ‘-l’ flag, and we can that there is no link available now; however, containers created earlier are still running.

Example #3

Delete the attached anonymous volume while deleting the container.

Step 1: First, we need to create a container with an anonymous volume attached to it to accomplish this scenario. Here is the command to create a container with anonymous volume:

Code:

docker run -d -v /root --name test-cont alpine

Step 2: Now, we can use the ‘-v’ option to delete the container as well as associated anonymous volume to the container as shown below:

Code:

docker rm -v test-cont

Output:

Explanation:

• In the above example, we can see that there was no volume before creating the container, and there is a volume created after container creation.
• That volume is anonymous volume, so we have used the ‘-v’ flag to remove the anonymous volume along with the container.

Example #4

Delete all containers that are in exited state.

We can use the ‘docker ps’ command to query the exited containers first, and then we can pass it to the ‘docker rm’ command as below:

Code:

docker ps -a

Output:

Code:

docker rm $(docker ps -a -q)

Output:

Explanation:

• In the above snapshot, we have a few stopped containers and one running container, and when we ran the command, it deleted all the stopped containers but not the running one; however, if we use the ‘-f’ option, then it will delete all the containers exits on the host.

Advantages of Docker rm

Given below are the advantages mentioned:

• It is an easy and quick way to remove containers as compared to the ‘docker container rm’ command.
• We do not have to clean up the anonymous volumes as it removes those volumes along with the container; if we use the ‘-v’ option, that is cool.

Rules and Regulations for Using a rm

Given below are the rules and regulations mentioned:

• First, it only removes stopped containers by default.
• Second, it only removes anonymous volumes attached to the container using the ‘-v’ flag, not the named volumes.
• Finally, it removes the link by using the ‘-l’ option and not the containers.

Conclusion

We have two commands to remove the containers in Docker, and the other one is the ‘docker container rm,’ and there is no difference between them; however, we can see that the ‘docker rm’ command is a little faster to work with.

Recommended Articles

This is a guide to Docker rm. Here we discuss the introduction, working, examples, advantages, rules, and regulations, respectively. You may also have a look at the following articles to learn more –

1. Docker Export
2. Docker Repositories
3. Dockerfile
4. Docker Essentials