Comment 13 for bug 191514

A good point in a comment earlier:

"A small warning dialog like "Warning: the package manager is working right now, it is strongly recommended to wait for it to finish." and the user's options could be like "proceed anyways / wait and proceed / cancel".
Of course this could also be a text-based dialog if you're going to call poweroff, reboot or pm-whatsoever from shell."

Unattended upgrades is often the update method of choice on the computers of numerous non-computer-savvy desktop users - the more informed friends/relatives turn it on to keep the security up-to-date without user interaction, which may not be possible because the user doesn't know the superuser password required for the upgrade.

In this case, a clear warning for the user would be useful, in order to prevent the confused user from forcibly shutting down the computer (by pulling the plug, for example). The easiest way to do this would probably be a LOCALIZED uppercase message in the stdout. Something like "ATTENTION! THE COMPUTER IS PERFORMING AUTOMATIC SECURITY UPDATES, AND WILL SHUT DOWN AUTOMATICALLY AFTER HAVING FINISHED. PLEASE DON'T TURN THE COMPUTER OFF MANUALLY!"

(For a possible more GUIly way of printing the message, see a deferred Karmic spec: https://wiki.ubuntu.com/FoundationsTeam/Specs/KarmicUpdatesOnShutdown )