When using Unraid, one has a docker.img file that’s usually housed at /mnt/cache/docker.img. This file is 20 GB by default and is responsible for

If this image ever uses all the allocated storage, your Docker containers will begin to act unexpectedly and eventually Unraid will be unable to start the service. You’ll experience some error like:

Docker service failed to start

Before you attempt to reduce the size of your docker.img file, you should root cause what caused it to inflate.

Once done stop Docker by going to Settings > Docker and turning it off. Then we’ll backup the existing docker.img:

$ cd /mnt/cache

$ cp docker.img docker.img.backup

At this point we can delete the docker.img by using the Settings > Docker

Delete Image File


Now we have to restart our Docker containers. Fortunately our container’s settings are saved, so we just have to apply the forms for each container we want to start. My advice is to use the

Previous Apps

page to get a list of all your previously installed apps.

At this point you should have a fresh docker.img and be able to start and stop your Docker containers.