I've been trying to set up a BTRFS system with snapshots similar to the layout that OpenSUSE has, and encountered somewhat of a roadblock. My current subvolume layout is nearly identical to OpenSUSE's, with @var being a separate subvolume (so anything in /var/ is not snapshotted).

However, this has led to some difficulties such as uninstalled packages showing as installed after reverting to a pre-installation snapshot (despite the files no longer being on the system). I assume this is due to /var/lib/pacman being excluded from snapshots.

Another issue I had was installed packages not present in the installed and local repo databases after reverting to a pre-uninstallation snapshot, leading to the package being present on my system but not showing in pacman -Qs <package> nor pacman -Ss <package> (searching the local repo). The only way I could uninstall said package was to reinstall it forcefully, using the --overwrite flag in pacman, and then uninstalling it.

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For reference, the local repository and its .db file that I use to contain my AUR packages is located at /var/cache/pacman/aur-local, alongside the pacman /pkg cache directory, where pacman packages go in /pkg and my built AUR packages go in /aur-local. My cloned PKGBUILDs go into ~/.cache. With my current setup where the entirety of /var is a subvolume, this is excluded from snapshots.

I've seen some example layouts in the Arch wiki and forums, with some citing to make subvolumes for /var/cache, /var/log, /var/spool, /var/tmp, and /var/machines. Does anyone know what layout is most recommended (in regards to /var) to prevent the issues I described above?