Not-very-well-thought-out-examples:
http - Always returns 404.
https - Always returns 404.
ipp - Returns whatever IPP says for "printer not found" or equivalent.
lpd - Takes data, does nothing with it.
dns - Always returns NXDOMAIN.
ident - Always returns nobody:nogroup
telnet - Accepts any username/password/credentials, returns "This account is not available" and immediately exits.
ssh - Accepts any username/password/credentials, returns "This account is not available" and immediately exits.
smtp - Accepts message, doesn't do anything with it.
pop3/imap - Accepts any login, always has 0 messages.
irc - Accepts any nick, PRIVMSG or other commands, commands don't actually do anything. Returns null list of channels and users when queried.
vnc - ?
rdp - ?
Etc.
Of course it was never meant as a place to store users files temporarily, it was always for programs that needed to write a temporary file.
We had a BSD system and an Ultrix system. For convenience I temporarily NFS mounted the root of the Ultrix system into /tmp/foo on the BSD machine. After I was done I forgot to umount the volume.
The next day, the Ultrix machine behaved really weird. Things seemed to work fine, but a lot of files were missing. It took a bit of troubleshooting before we figured out what had happened.
As it turns out, the nightly /tmp cleanup script had run on the BSD machine, and this script deleted all files which had not been accessed in a week. Of course the script had traversed the NFS mount and cleaned up everything on the root disk of the other machine. This meant that all the files that were commonly used were still there, so things seemed fine until you tried to do anything that involved files that hadn't been touched in the last week.
That's when I learned never to use /tmp for anything important.
https://www.reddit.com/r/talesfromtechsupport/comments/22ke8...
https://www.reddit.com/r/talesfromtechsupport/comments/c24q2...
https://www.reddit.com/r/talesfromtechsupport/comments/flgsn...
https://www.reddit.com/r/talesfromtechsupport/comments/65cam...
https://www.reddit.com/r/talesfromtechsupport/comments/bks9e...
https://www.reddit.com/r/talesfromtechsupport/comments/9wrsc...
> IT: This is the trash bin, you would move files here to delete them off of your computer.
> CW: IT IS NOT A TRASH CAN, IT IS A RECYCLING BIN! IT SAYS SO RIGHT UNDER THE ICON!
Ok, now wait a second, why the hell is it called a recycling bin anyway?
"Recycling" doesn't mean "plan to throw this away later, but maybe I'll still grab it out of the trash can in case I made a mistake." Who came up with this metaphor?
The word you are looking for is "copying".
I'd honestly prefer if the policy would at least excempt reasonably small files or textfiles.