Today I’ve had some spare time and felt adventurous and decided to try out the linux device mapper snapshots eventhough I couldn’t find any documentation about it. Neither how it works in urbackup nor in general. When looking for general documentation, I always only find information about lvm. Anyway.
After installing the urbackup client, it offered, to change the root device to a dm device (or something similar) to which I said yes. That worked so far, also after reboots. I don’t really now what exactly it did, and how I could undo those changes.
Then after some mainly unsuccessful tests and restarts I realized that I had no disk space left.
As it seems there where quite a lot of /.overlay_2fefd007-* files of 5GB size which filled up my complete disk space.
When the machine does a restart while doing a backup, those files just stay. Also when the backup fails the file stays (not always but often, more testing needed there).
The annoying part about is, you can’t just delete those files.
First you need to execute
chattr -i .overlay_2fefd007*
Which is easy enough, if you know it…
Also a lot of times the backup just gets stuck for hours in indexing, seemingly not doing anything (the overlay file was already created then) while when it works, the indexing only takes a few minutes.
I’ve managed to get a debug log from the backupclient when that happens. I’ve truncated it, it just continues like that for hours…
urb.log (19.4 KB)
My best guess is that something fails in /usr/local/share/urbackup/dm_create_snapshot and urbackup doesn-t properly handle that.
But without proper documentation about what is supposed to exactly happen and debug output from urbackup, it’s difficult to debug for me.
Anyway, it would be a cool features if it worked properly. I’d be willing to do some further testing, but would need some help there…