Removing Docker Images, Containers, and Volumes with Ease

Docker whales gobbling up all your memory, bruh?

Don’t have docker installed? Check out this previous post:

As of this write-up, I am currently using:

• Docker version 17.03.1-ce, build c6d412e on macOS Sierra Version 10.12.4

You can verify your version with:

$ docker version

Introduction

Docker makes it easy to wrap your applications and services in containers so you can run them anywhere. As you work with Docker, however, it’s also easy to accumulate an excessive number of unused images, containers, and data volumes that clutter the output and consume disk space.

Docker doesn’t provide direct cleanup commands, but it does give you all the tools you need to clean up your system from the command line. This cheat sheet-style guide provides a quick reference to commands that are useful for freeing disk space and keeping your system organized by removing unused Docker images, containers, and volumes.

TL;DR

Skip the foreplay and remove all unused containers, networks, images (both dangling and unreferenced), and optionally, volumes.

sudo docker system prune -a

Using the Cheat Sheet

• This guide is in cheat sheet format with self-contained command-line snippets.
• Jump to any section that is relevant to the task you are trying to complete.

The command substitution syntax:

command $(command)

This is available in many popular shells such as bash, zsh, and Windows PowerShell.

Removing Docker Images

Use the Docker images command with the -a flag to locate the ID of the images you want to remove. This will show you every image, including intermediate image layers. When you’ve located the images you want to delete, you can pass their ID or tag to Docker rmi:

List:

docker images -a

Remove:

docker rmi image

Remove Dangling Images

Docker images consist of multiple layers. Dangling images are layers that have no relationship to any tagged images. They no longer serve a purpose and consume disk space. They can be located by adding the filter flag, -f with a value of dangling=true to the Docker images command. When you’re sure you want to delete them, you can add the -q flag, then pass their ID to Docker rmi:

Note: If you build an image without tagging it, the image will appear on the list of dangling images because it has no association with a tagged image. You can avoid this situation by providing a tag when you build, and you can retroactively tag an images with the Docker tag command.

List:

docker images -f dangling=true

Remove:

docker rmi $(docker images -f dangling=true -q)

Removing Images According to a Pattern

You can find all the images that match a pattern using a combination of Docker images and grep. Once you’re satisfied, you can delete them by using awk to pass the IDs to Docker rmi. Note that these utilities are not supplied by Docker and are not necessarily available on all systems:

List:

docker ps -a | grep "pattern"

Remove:

docker images | grep "pattern" | awk '{print $1}' | xargs docker rm

Remove all Images

All the Docker images on a system can be listed by adding -a to the Docker images command. Once you’re sure you want to delete them all, you can add the -q flag to pass the Image ID to Docker rmi:

List:

docker images -a

Remove:

docker rmi $(docker images -a -q)

Removing Docker Containers

Use the Docker ps command with the -a flag to locate the name or ID of the containers you want to remove:

List:

docker ps -a

Remove:

docker rm ID_or_Name

Remove a Container Upon Exit

If you know when you’re creating a container that you won’t want to keep it around once you’re done, you can run Docker run — rm to automatically delete it when it exits.

Run and Remove:

docker run -rm image_name

Remove all Exited Containers

You can locate containers using Docker ps -a and filter them by their status: created, restarting, running, paused, or exited. To review the list of exited containers, use the -f flag to filter based on status. When you’ve verified you want to remove those containers, using -q to pass the IDs to the Docker rm command.

List:

docker ps -a -f status=exited

Remove:

docker rm $(docker ps -a -f status=exited -q)

Remove Containers Using More Than One Filter

Docker filters can be combined by repeating the filter flag with an additional value. This results in a list of containers that meet either condition. For example, if you want to delete all containers marked as either Created (a state which can result when you run a container with an invalid command) or Exited, you can use two filters:

List:

docker ps -a -f status=exited -f status=created

Remove:

docker rm $(docker ps -a -f status=exited -f status=created -q)

Remove Containers According to a Pattern

You can find all the containers that match a pattern using a combination of Docker ps and grep. When you’re satisfied that you have the list you want to delete, you can use awk and xargs to supply the ID to Docker rmi. Note that these utilities are not supplied by Docker and not necessarily available on all systems:

List:

docker ps -a | grep "pattern”

Remove:

docker ps -a | grep "pattern" | awk '{print $3}' | xargs docker rmi

Stop and Remove all Containers

You can review the containers on your system with Docker ps. Adding the -a flag will show all containers. When you’re sure you want to delete them, you can add the -q flag to supply the IDs to the Docker stop and Docker rm commands:

List:

docker ps -a

Remove:

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

Removing Docker Volumes

Use the Docker volume ls command to locate the volume name or names you wish to delete. Then you can remove one or more volumes with the Docker volume rm command:

List:

docker volume ls

Remove:

docker volume rm volume_name

Remove Dangling Volumes

Since the point of volumes is to exist independent from containers, when a container is removed, a volume is not automatically removed at the same time. When a volume exists, and is no longer connected to any containers, however, it’s called a dangling volume. To locate them to confirm you want to remove them, you can use the Docker volume ls command with a filter to limit the results to dangling volumes. When you’re satisfied with the list, you can add a -q flag to provide the volume name to Docker volume rm:

List:

docker volume ls -f dangling=true

Remove:

docker volume rm $(docker volume ls -f dangling=true -q)

Remove a Container and its Volume

If you created an unnamed volume, it can be deleted at the same time as the container using the -v flag. Note that this only works with unnamed volumes. When the container is successfully removed, its ID is displayed. Note that no reference is made to the removal of the volume. If it is unnamed, it is silently removed from the system. If it is named, it silently stays present.

Remove:

docker rm -v container_name

Conclusion

This guide covers some of the common commands used to remove images, containers, and volumes. There are many other combinations and flags that can be used with each. For a comprehensive guide to what’s available, see the Docker documentation for Docker rmi, Docker rm and Docker volume rm.

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