The University of Minnesota has an Acceptable Use Policy. It is unreadable legalese except for an appendix of Acceptable Use Guidelines. For emphasis we repeat some of this here and also add some UNIX-specific guidelines.

• Choose a good password for your account.
• Do not let other people use your account. Do not reveal your password to anyone for any reason (this includes the system administrators).
• Security attacks on our computers or anyone else's are strictly forbidden.
• You are responsible for understanding how UNIX file permissions work and using them to protect the privacy of information in your account.
• Regardless of any other considerations, cheating on exams and plagarism are unacceptable. It is not a defense to claim that any files read in the process of cheating or plagarism had file permissions that made them publically readable.
• Regardless of any other considerations, reading e-mail of other users is unacceptable. File permissions prevent this if set correctly, but it is wrong to attempt this even if file permissions are not set correctly.
• Tying up a computer for long periods of time is unacceptable.
  • Don't leave a computer with the screen lock on for a long time.
  • Run big jobs at low priority using the UNIX nice and renice commands. Use the lowest possible priority (nice +19 or renice -n 19) unless there are other competing background jobs.
  • Get permission before running big jobs on any of the faculty machines.
  • Do not run multiple jobs simultaneously on any machine. Use a shell script that runs them consecutively.