howto/upgrades.md

@@ -141,6 +141,27 @@ Logging into the LDAP server (currently `alberti`) and killing all the
    
    pkill -u sshdist ssh
 
+## systemd user manager services
+
+The `needrestart` tool [lacks](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=843778)
+the ability to restart user-based systemd daemons and services. Example
+below, when running `needrestart -rl`:
+
+    User sessions running outdated binaries:
+     onionoo @ user manager service: systemd[853]
+     onionoo-unpriv @ user manager service: systemd[854]
+
+To restart these services, this command may be executed:
+
+    systemctl restart user@$(id -u onionoo) user@$(id -u onionoo-unpriv)
+
+Sometimes an error message similar to this is shown:
+
+    Job for user@1547.service failed because the control process exited with error code.
+
+The solution here is to run the `systemctl restart` command again, and
+the error should no longer appear.
+
 ## Ganeti
 
 The `ganeti.service` warning is typically an OpenSSL upgrade that