There are various options available for notifying end users about software update installations, installation progress, and restarts.
Patch Management 8.x
Information on configuring installations and restart notifications and be found in our Tech Docs page, Default Software Update Plug-in Policy Page.
Note that changes were introduced in 8.7.1 that give the option to restart automatically or not if no user is logged in. Prior to 8.7.2, computers will restart if needed automatically if no user is logged in.