howto/upgrades.md

@@ -400,6 +400,9 @@ entered at boot time, either through the initramfs (if it has the
 the case for the `mandos-01` server itself, for example, as it
 currently can't unlock itself, naturally.
 
+Note that you can cancel a reboot with `--kind=cancel`. This also
+cascades down Ganeti nodes.
+
 ## Batch rebooting multiple hosts
 
 IMPORTANT: before following this procedure, make sure that only a