Archlinux provides a set of systemd units for automating regular btrfs scrubs on local file systems: https://git.archlinux.org/svntogit/packages.git/tree/trunk?h=packages/btrfs-progs Currently we need to manually write (or copy) these systemd units to automate regular file system scrubs. It would be nice if we could do the same with a USE=systemd flag on btrfs-progs.
Why would one want to pollute packages with arbitrary services? Then you could do the same for cron users. And if you want other scrub intervals, you have to edit the files yourself anyway.
The same argument could be said for many packages which provide helpful systemd units, for example zfs. They are included with USE=systemd and it's your prerogative to use them.
All of this is in sys-fs/btrfsmaintenance. Which contains all these services: /lib64/systemd/system/btrfs-balance.service /lib64/systemd/system/btrfs-defrag.service /lib64/systemd/system/btrfs-scrub.service /lib64/systemd/system/btrfs-trim.service /lib64/systemd/system/btrfsmaintenance-refresh.service /lib64/systemd/system/btrfs-balance.timer /lib64/systemd/system/btrfs-defrag.timer /lib64/systemd/system/btrfs-scrub.timer /lib64/systemd/system/btrfs-trim.timer
That looks great. Maybe the better fix is to instead emit a message when emerging with USE=systemd alerting that sys-fs/btrfsmaintenance exists if needed.