howto/upgrades.md

@@ -354,13 +354,16 @@ those services directly in needrestart.
 # Reboots
 
 Sometimes it is necessary to perform a reboot on the hosts, when the
-kernel is updated. Nagios will warn about this, with something like
-this:
+kernel is updated. Prometheus will warn about this with the
+`NeedsReboot` alert, which looks like:
 
-    WARNING: Kernel needs upgrade [linux-image-4.9.0-9-amd64 != linux-image-4.9.0-8-amd64]
+    Servers running bookworm neeeds to reboot
 
-TODO: the above is the old way, the needrestart check has a different
-output. document it above.
+You can see the list of pending reboots with this Fabric task:
+
+    fab fleet.pending-reboots
+
+See below for how to handle specific situations.
 
 ## Rebooting a single host