Suddenly having backup failures

I’ve started having backup failures after a recent update. Looking through the log, it seems that the issue is caused by a lack of disk space:

[2023-09-18 20:30:34] EXCEPTION: /var/www/discourse/lib/discourse.rb:138:in `exec': Failed to gzip archive.

gzip: /var/www/discourse/public/backups/default/aoda-forum-2023-09-18-202648-v20230913194832.tar.gz: No space left on device

However, df -h gives 7.5GB free. I’m backing up to AWS, and user uploads are at 5.9GB. Digging a little deeper, I did find that /var/lib/docker/aufs is using 15GB while /var/discourse uses 12GB. There are no other containers, services, etc on this machine.

I have, of course, already run launcher cleanup.

In short, my questions are:

  1. What is going on with the backups? Is it really disk space related or something else?
  2. /var/aufs/ seems to be using a lot of space. Is there a safe way to clean that up?

You need enough space to hold the uncompressed database and the images.