As you work with containers, many containers are created, tested, and abandoned during their lifecycle. In due course of time, you may be piling up containers and images in your workspace in host system. Therefore it is important to identify unnecessary containers and images to clean them up every now and then from your work environment. Otherwise, docker can gradually eat up the disk space of host machine.
You will learn how to clean up your unwanted containers and images that you no longer need them.
Containers are still persisted, even though they are stopped.
If you want to delete them from your server you need to use the docker container rm command.
docker container rm can take either the CONTAINER ID or NAME as seen above. Try to remove the hello-world container:
$ docker container ls -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6a9246ff53cb hello-world "/hello" 18 seconds ago Exited (0) 16 seconds ago ecstatic_cray
$ docker container rm 6a9246ff53cb # container with STATUS marked as exited
The container is now gone when you execute ls -a command to check the current situation.
what if there are several such containers to be deleted? Well, you can list those container IDs with the following command:
docker rm <container-id1> <container-id2> ...
or you can use filter flag to remove exited containers:
docker rm $(docker ps -qa –filter status=exited)
more useful commands:
docker stop $(docker ps -a -q) # stops all running containers
docker rm $(docker ps -a -q). # removes all running containers
You deleted the container instance above, but not the image of hello-world itself. Real-world docker images comprise multiple layers to run code within a container. Old and outdated images can clutter your system, taking up storage space and making searches more cumbersome. In our case, you do not need e.g., hello-world image anymore so let us delete it.
First of all, list all the images you have downloaded to your computer:
$ docker image ls
REPOSITORY TAG IMAGE ID CREATED SIZE
alpine latest 053cde6e8953 9 days ago 3.97MB
hello-world latest 48b5124b2768 10 months ago 1.84kB
Here you can see the images downloaded as well as their sizes.
To remove the hello-world image use the docker image rm command together with the id of the docker image.
sofus@praq-sal:~$ docker image rm 48b5124b2768
Untagged: hello-world:latest
Untagged: hello-world@sha256:c5515758d4c5e1e838e9cd307f6c6a0d620b5e07e6f927b07d05f6d12a1ac8d7
Deleted: sha256:48b5124b2768d2b917edcb640435044a97967015485e812545546cbed5cf0233
Deleted: sha256:98c944e98de8d35097100ff70a31083ec57704be0991a92c51700465e4544d08
and obviously, you can remove multiple images as below:
docker rmi
Normally these images are unused and only use up disk space. We can find them by using the -f filter option with the string dangling=true. They can be purged afterwards.
To view dangling images use the below command:
$ docker images –f dangling=true
to delete or remove dangling images use
$ docker images purge
In the process of pulling, building and running images for our daily needs, we often end-up downloading several of images. These images will not be deleted as docker takes a very conservative approach to clean up. Docker provides a prune command, taking all dangling containers/images/networks/volumes.
docker container prunedocker image prunedocker network prunedocker volume pruneThe docker image prune command allows you to clean up unused images. By default, docker image prune only cleans up dangling images. A dangling image is one that is not tagged and is not referenced by any container. To remove all unused resources, resources that are not directly used by any existing containers, use the -a switch as well.
If you want a general cleanup, then docker system prune is your friend.
We have seen how to identify the unused docker containers/images and clean them up from working space.