In the mid-2000ds, there eventually came a time when the xlock (Ex-lock) screen locker disappeared from the last university workstations that still had it. People routinely got puzzled when they could not run it. It was a fun prank to tell them that Ex-Cee-lock was the replacement for it (which would, of course, run the clock application). :)
Xlocking workstations became a problem at our university. People would claim a workstation, lock it, go do something else (lunch, lecture) and then come back to their reserved workstation. So the admins added a button that you could log someone out if the screen had been locked for more than half an hour.
They didn't want to ban xlock because they cared about security.
> So the admins added a button that you could log someone out if the screen had been locked for more than half an hour.
In our CS labs the PCs re-imaged themselves on boot⁰, from a choice of OS images¹, so you didn't have to worry about causing corruption of the machine by just power-cycling it to get around the locked status. This meant that locking a workstation to reserve it didn't work.
My workaround to that² was to set the wallpaper which displayed behind the unlock prompt to an image of a bluescreen indicating a hardware error and move the window containing the lock prompt to the for bottom right of the screen, so it was just a single pixel and not easily noticed. Hey presto: a locked machine that no one wanted to claim by restarting because it looked faulty. Obviously anyone with half a brain watching me unlock the machine a short while later would immediately work out the trick, so the knowledge spread soon enough and the ruse stopped being as effective. It was very effective for a while.
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[0] from the same shared network drive, which was initially a problem (this was the first year that lab had been in operation) if several machines re-imaged at the same time as head thrashing caused IO throughout to fall through the floor. Later revisions of the setup helped by tweaking cache settings, and giving the server more RAM, so that the second and subsequent read of an image in a given period would come from cache, also the images were compressed for the same reason and also to reduce the second bottleneck: the glut of traffic through the server's single 100mbit NIC.
[1] usually just Windows NT and the local Linux build, but sometimes other options were present
[2] which I used very occasionally, partly to not be a dick but mainly so as to not give the game away to quickly
Windows NT could always remotely log out the current user when part of a domain. We had tools in place for our lab administrators to logout users if they found locked workstations. With Windows 2000 you could automate this through group policy
In high school I'd reserve workstations for my friends by unplugging the keyboard. The PC would fail to boot with "Keyboard not found, press F1 to continue" which was enough to get it designated broken and avoided.
I did this unintentionally in college once by switching the keyboard layout to Dvorak, which for some reason persisted across logins. I came back later that day to the same lab and the station I had been using was marked "Out of Order". Huh, that's weird. Sat down at the station next to it. Next day both of them were marked "Out of Order". Oh, huh. Is there something weird with the keyboard? I might know what happened...
