feat: add zfs-scrub systemd units (#146)

Co-authored-by: Benjamin Sherman <[email protected]>

README.md

@@ -532,6 +532,20 @@ If you do forget to specify the mountpoint, or you need to change the mountpoint
 # zfs set mountpoint=/var/tank tank
 ```
 
+#### ZFS scrub timers
+
+It's good practice to run a `zpool scrub` periodically on ZFS pools to check and repair the integrity of data. This can be easily configured with ucore by enabling the timer. There are two timers available: weekly and monthly.
+
+```bash
+# Substitute <pool> with the name of the zpool
+systemctl enable --now zfs-scrub-weekly@<pool>.timer
+
+# Or to run it monthly:
+systemctl enable --now zfs-scrub-monthly@<pool>.timer
+```
+
+This can be enabled for multiple storage pools by enabling and starting a timer for each.
+
 #### Sanoid/Syncoid
 
 sanoid/syncoid is a great tool for manual and automated snapshot/transfer of ZFS datasets. However, there is not a current stable RPM, rather they provide [instructions on installing via git](https://github.com/jimsalterjrs/sanoid/blob/master/INSTALL.md#centos).

ucore/usr/lib/systemd/system/zfs-scrub-monthly@.timer

@@ -0,0 +1,12 @@
+[Unit]
+Description=Monthly zpool scrub timer for %i
+Documentation=man:zpool-scrub(8)
+
+[Timer]
+OnCalendar=monthly
+Persistent=true
+RandomizedDelaySec=1h
+Unit=zfs-scrub@%i.service
+
+[Install]
+WantedBy=timers.target

ucore/usr/lib/systemd/system/zfs-scrub-weekly@.timer

@@ -0,0 +1,12 @@
+[Unit]
+Description=Weekly zpool scrub timer for %i
+Documentation=man:zpool-scrub(8)
+
+[Timer]
+OnCalendar=weekly
+Persistent=true
+RandomizedDelaySec=1h
+Unit=zfs-scrub@%i.service
+
+[Install]
+WantedBy=timers.target

ucore/usr/lib/systemd/system/zfs-scrub@.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=zpool scrub on %i
+Documentation=man:zpool-scrub(8)
+Requires=zfs.target
+After=zfs.target
+ConditionACPower=true
+ConditionPathIsDirectory=/sys/module/zfs
+
+[Service]
+EnvironmentFile=-@initconfdir@/zfs
+ExecStart=/bin/sh -c '\
+if /usr/sbin/zpool status %i | grep -q "scrub in progress"; then\
+exec /usr/sbin/zpool wait -t scrub %i;\
+else exec /usr/sbin/zpool scrub -w %i; fi'
+ExecStop=-/bin/sh -c '/usr/sbin/zpool scrub -p %i 2>/dev/null || true'