Docker Remove Unused Volumes

In this guide, we'll walk through various use cases on how to handle and remove unused Docker volumes.

Why is Removing Unused Volumes Important? 

Reclaim Disk Space: Unused volumes, especially those containing old logs or data, can eat up disk space. 

Maintain Docker Environment: A tidy workspace aids in effective management and reduces potential conflicts. 

Enhanced Performance: Removing unnecessary volumes can lead to faster backup times and container operations. 

Removing Single Unused Volume 

Before removing all unused volumes, it might be beneficial to review and delete individual volumes. Here’s how you can do that:

docker volume rm VOLUME_NAME_OR_ID

If the volume is in use or doesn't exist, Docker will throw an appropriate error. 

Safely Removing All Unused Volumes 

Docker provides a straightforward command to delete all volumes not associated with any container:

docker volume prune

Upon executing this command, Docker will prompt you for a confirmation, as the data inside these volumes will be irreversibly deleted.

For example:

$ docker volume prune
WARNING! This will remove all local volumes not used by at least one container.
Are you sure you want to continue? [y/N] y

Deleted Volumes:
unused_volume2, unused_volume3, unused_volume4

Total reclaimed space: 1.5GB

Identifying Unused Volumes 

Before you decide to prune, it might be beneficial to list the volumes and check which ones aren’t in use. This can be done using:

docker volume ls -f dangling=true

For example:

$ docker volume ls -f dangling=true
DRIVER    VOLUME NAME
local     unused_volume5
local     unused_volume6

The -f flag with the dangling=true filter shows only the unused volumes.

What if I have a Volume Attached to a Stopped Container? 

Volumes attached to stopped containers are considered "used" by Docker. So, the docker volume prune won't remove such volumes. If you're certain you want to delete such volumes, you'd need to delete the associated container first.

Conclusion

Managing storage in Docker involves more than just allocating space for your containers. Periodic reviews and cleanups ensure your Docker environment remains efficient, organized, and primed for performance. Always remember to take necessary backups and ensure you aren't deleting essential data. Happy Dockering!

Related Volume Management Guides

• Docker Create Volume
• Docker List Volumes
• Docker Remove Volumes
• Docker Remove Unused Volumes
• All Docker Tutorials and Guides