howto/upgrades.md

@@ -321,8 +321,9 @@ The above covers all upgrades that are automatically applied, but some
 are blocked from automation and require manual intervention.
 
 Others do upgrade automatically, but require a manual
-restart. Normally, [needrestart](https://github.com/liske/needrestart) runs after upgrades and takes care
-of restarting services, but it can't actually deal with everything. 
+restart. Normally, [needrestart](https://github.com/liske/needrestart) runs
+after upgrades and takes care of restarting services, but it can't actually deal
+with everything. 
 
 Our alert in Alertmanager only shows a sum of how much hosts have pending
 restarts. To check the entire fleet and simultaneously discover which hosts are
@@ -330,6 +331,9 @@ triggering the alert, run this command in [Fabric](howto/fabric):
 
     fab fleet.pending-restarts
 
+Note that you can run the above in debug mode with `fab -d
+fleet.pending-restarts` to learn exactly which service is affected on each host.
+
 If you cannot figure out why the warning happens, you might want to
 run `needrestart` on a particular host by hand: