Actually not bad advice. I could see that all of these datasets have been created on 17.02.2021. I checked my .bashhistory and could not find anything. I have not logged that I installed any software on this day and the next Manjaro update was only a few days later.
I just mounted one of them and it contains this:
[[email protected] mount]$ ls -al
drwxr-xr-x 23 root root 26 17. Feb 22:05 .
drwxr-xr-x 8 root root 8 5. Mär 12:58 ..
drwxr-xr-x 3 root root 3 16. Feb 20:18 app
drwxr-xr-x 2 root root 289 16. Feb 07:30 bin
drwxr-xr-x 2 root root 2 16. Feb 07:30 config
drwxrwxr-x 2 root root 3 16. Feb 20:15 defaults
drwxr-xr-x 4 root root 5 17. Feb 22:05 dev
-rwxr-xr-x 1 root root 0 17. Feb 22:05 .dockerenv
-rwxrwxr-x 1 root root 3625 16. Feb 07:29 docker-mods
drwxrwxr-x 28 root root 55 17. Feb 22:05 etc
drwxr-xr-x 2 root root 2 16. Feb 07:30 home
-rwxr-xr-x 1 root root 389 13. Mai 2020 init
drwxr-xr-x 6 root root 30 16. Feb 20:18 lib
drwxr-xr-x 2 root root 5 12. Mai 2020 libexec
drwxr-xr-x 5 root root 5 16. Feb 07:30 media
drwxr-xr-x 2 root root 2 16. Feb 07:30 mnt
drwxr-xr-x 2 root root 2 16. Feb 07:30 opt
dr-xr-xr-x 2 root root 2 16. Feb 07:30 proc
drwx------ 3 root root 3 16. Feb 20:17 root
drwxr-xr-x 2 root root 2 16. Feb 07:30 run
drwxr-xr-x 2 root root 69 16. Feb 07:30 sbin
drwxr-xr-x 2 root root 2 16. Feb 07:30 srv
drwxr-xr-x 2 root root 2 16. Feb 07:30 sys
drwxrwxrwt 2 root root 2 16. Feb 20:18 tmp
drwxrwxr-x 9 root root 9 16. Feb 20:18 usr
drwxr-xr-x 12 root root 13 16. Feb 07:30 var
The .dockerenv file as well as the fact that some of the files are dated may 2020 let me think that docker my be the culprit. My system has not been running since may and this seems like some imported filesystem.
I think it is docker, just reading up on it and found this:
The btrfs and zfs storage drivers are used if they are the backing filesystem (the filesystem of the host on which Docker is installed). These filesystems allow for advanced options, such as creating “snapshots”, but require more maintenance and setup. Each of these relies on the backing filesystem being configured correctly. - Docker storage drivers | Docker Documentation
Edit: Yes it is indeed docker. If you leave it unconfigured it defaults to the zfs driver and just creates new datasets in the same dataset where /var/lib/docker is located at. Since the docker folder was located in my root dataset it started to create it’s own legacy datasets there. I stopped docker, recursivly removed all legacy datasets, created a new dataset with mountpoint set to /var/lib/docker and pulled an image. This is the result:
I can’t mark it as a solution. I can make it a wiki and report it, but marking it as a solution is not an option for me .
Edit: Additionally I will have to think about if I want to keep the zfs docker driver or switch back to another one. On the one hand I can imagine docker utilizing the ZFS feature set can be a huge performance plus, on the other hand the more I use docker every time I list my datasets I will have a cluttered output.