https://bugs.launchpad.net/ubuntu-release-upgrader/+bug/1674661

As a long-time Ubuntu fan and proponent, I have always thought this wouldn't be an issue anymore, but it apparently is: The OS and GUI are active and appear to be visibly "working" to most people during a major system upgrade, and there are no major warnings presented to the user *not* to use his or her PC while in this major upgrade process.

This, as I was getting to, is a problem that needs to be addressed and therefore fixed.

Reason being:
When major system components and apps are being upgraded while the user is still in full (UI) control of his or her PC, the user is prone to opening the wrong programs at the wrong time, rebooting or shutting down the PC unnecessarily, unintentionally breaking his or her system(s).
Furthermore, opening a wrong program at the wrong time or attempting to change settings can cause issues during the upgrade, unwanted program access and file access locks (either locks the user or locks the upgrader package), all which can lead to dpkg errors, apt-get problems, aptitude crashes, and (most importantly) broken systems.

I'm proposing the Ubuntu development team devise a way for "ubuntu-release-upgrader" to put a lock on the "Ubuntu-Desktop" UI , desktop manager, and window manager during the upgrade process to prevent the user from accidentally causing an upgrade malfunction.