How to Remove Docker Images, Containers, and Volumes

As a fellow Docker user, I‘m sure you know how easy it is for old images, stopped containers, and unused volumes to accumulate, slowly eating away at your disk space. After running Docker for a while, you may discover GBs worth of old artifacts that aren‘t being used for anything useful.

Not to worry! In this guide, I‘ll show you how to thoroughly clean up Docker and free up space by removing old images, containers, volumes, networks and more. By the end, you‘ll have a lean and mean Docker installation.

Here‘s what we‘ll cover:

• Common sources of Docker disk bloat
• Deleting stopped containers
• Removing unused images
• Pruning volumes, networks, and build cache
• Preventing future Docker buildup
• Advanced cleanup commands

Follow these tips, and you can reclaim tens of gigabytes of space easily. Let‘s dive in!

Common Causes of Docker Disk Usage Buildup

Before cleaning up Docker, it helps to understand what‘s typically eating up all your disk space in the first place:

Dangling images – These are layers and intermediate images that were built during the image creation process but are no longer associated with an image tag. They sit around taking up space.

Unused volumes – Volumes created but not mounted to any active containers.

Stopped containers – Exited containers still retain their full filesystem and configuration.

Build cache – Docker caches image layers to speed up subsequent builds, but these cache layers pile up.

Intermediate containers – Containers created as part of a build process but not committed to an image.

A single Docker image may consist of dozens of layers totalling GBs. So even with just a moderate number of images, your Docker host can be bloated with huge amounts of unused data.

Now let‘s go through how to effectively clean each of these up.

Delete Stopped Containers

When you stop a container, it retains its full filesystem and configuration by default. So all those stopped containers from testing or development can really add up.

List all containers, running and stopped:

Delete a specific container by ID:

To remove all stopped containers:

This will delete all containers in an Exited status. Confirm the deletion when prompted.

As a point of reference, deleting all stopped containers on my Docker host recently freed up 26GB! So it‘s always good to prune your stopped containers periodically.

Pro tip: To have Docker automatically delete stopped containers, use --rm when starting the container:

Now let‘s move onto removing unused images taking up space.

Removing Unused and Dangling Docker Images

Unused images, sometimes called dangling images, are intermediate image layers and build cache created when building an image. They sit around hogging disk space unless you explicitly delete them.

To list your images:

Delete specific images by ID:

But to really remove unused and dangling images, use Docker‘s pruning commands:

When I ran these on my machine, they freed up 9GB andDeleted over 500 unused images!

You can also filter images by age or label to clean up:

Repeatedly pruning old or dangling images ensures you only maintain the images you actually need.

Prune Unused Volumes and Networks

Two other sources of Docker disk bloat are unused local volumes and networks.

List all volumes:

Remove specific volumes by name:

Prune all unused volumes:

You can do the same for networks:

Pruning removed 5 unused volumes and 4 orphan networks for me, freeing up a non-trivial amount of space.

Remove Build Cache with Docker Builder Prune

Intermediate containers created during builds and the cache Docker uses to speed up subsequent builds contribute to disk usage.

Use the docker builder prune command to clean up just this build cache:

Note this will not remove any running containers.

In my case, removing the build cache freed up 2GB alone!

Prevent Docker Disk Usage Build Up

Now that you‘ve cleaned up your Docker host, let‘s talk about some general strategies to prevent future buildup:

• Use --rm when running containers – This automatically deletes containers when stopped.
• Delete containers manually – Don‘t just stop containers. Delete them after use.
• Assign tags – Tag images so they aren‘t removed during prune commands.
• Limit volume mounts – Avoid mounting more volumes than needed.
• Leverage .dockerignore – Exclude files not needed in images.
• Use multi-stage builds – Reuse layers and minimize intermediate layers.
• Don‘t store data in containers – Use volumes for stateful container data.
• Remove build cache – Clean up cache once builds complete.
• Containerize apps only where useful – Avoid overusing containers where not needed.

Following Docker best practices prevents wasted space from piling up in the first place.

Advanced Docker Prune and Cleanup Commands

Here are a few more advanced Docker cleanup commands to really scrub things down.

Delete just dangling images not used by any containers:

Remove containers created more than a certain time threshold:

Delete images without at least one container associated:

Remove just unused volumes:

Clean up after Docker Compose by removing associated containers and images:

So in summary, here are some key Docker cleanup commands:

• docker system prune – Remove all unused containers, networks, images, and build cache
• docker container prune – Delete stopped containers
• docker image prune – Remove dangling images
• docker network prune – Delete unused networks
• docker volume prune – Remove unused volumes
• docker builder prune – Delete build cache

Conclusion

I hope these Docker removal and pruning commands give you the knowledge to thoroughly clean up your Docker system.

Keeping Docker lean improves performance, saves disk space, and makes it easier to manage your whole Docker installation.

The key is periodically removing stopped containers, dangling images, unused volumes and networks, and build cache with Docker‘s built-in prune commands.

Combine these prune commands with habits to prevent future buildup, and you‘ll have a slim, optimized Docker host in no time!