Added an update-protocol section to alpine-server-setup.

docs/alpine-server-setup/post-install/update-protocol.md

@@ -0,0 +1,52 @@
+# Update protocol
+
+ZFS opens up new methods to safely update the system. These methods are described in this section in combination with general practises to maintain ZFS filesystems.
+
+## Pre-update
+
+To be able to rollback the system after a system update one may create a snapshot of the root filesystem. 
+
+```
+# zfs snapshot tank/root/alpine@previous
+```
+
+> Tip: `zfs destroy` can be used to remove snapshots and `zfs list -t snapshot` can be used to list them.
+
+## Update
+
+Perform a system update.
+
+```
+# apk upgrade
+# reboot
+```
+
+If the system does not behave accordingly after reboot, one may rollback to the previous snapshot and further investigate from there.
+
+```
+# zfs rollback -r tank/root/alpine@previous
+```
+
+## Post-update
+
+To maintain the performance of the SSDs in the system, perform a trim on the zfs-pool.
+
+```
+# zpool trim --secure --wait tank
+```
+
+> Some devices may not support the option `--secure`, remove it then, if necessary.
+
+Thereafter, perform a scrub on the zfs-pool which checks and repairs the data in the pool.
+
+```
+# zpool scrub tank
+```
+
+This may take a while, the progress can be checked with:
+
+```
+# zpool status tank
+```
+
+> A ZFS scrub only repairs if mirror or a zraid mode is used in the pool.

mkdocs.yml

@@ -79,6 +79,7 @@ nav:
       - 'Logging': alpine-server-setup/post-install/logging.md
       - 'Swap': alpine-server-setup/post-install/swap.md
       - 'Users': alpine-server-setup/post-install/users.md
+      - 'Update protocol': alpine-server-setup/post-install/update-protocol.md
       - 'Containers': alpine-server-setup/post-install/containers.md
 
   - 'Void-desktop setup':