Essential System Administration, 3rd Edition

Troubleshooting Terminal Problems

Messed-up terminals are an occasional problem that system administrators have to deal with. When a terminal is hung (when it won’t respond to any input) or seems to have gone crazy, here are some things to try that address the most common causes:

• If the user knows what she did last, try to undo it. For example, if she was experimenting with stty options, try a stty sane command.

• If the terminal doesn’t respond at all, the user might have accidentally hit Ctrl-S, the pause key, the hold screen key, or something else that temporarily stops output. Try entering Ctrl-Q and then these other keys to see if things get going again.

• Check the terminal settings via its setup menu. In particular, is its baud rate set correctly?

• Try entering the reset command. If it doesn’t work, try preceding and following it with a line feed (Ctrl-J if the terminal has no line feed key):

                    ^Jreset^J

  Substituting stty sane in place of reset can also work. Running either command twice in succession is frequently necessary.

• If the user has turned the power off and back on, check other settings like the emulation mode. If the user hasn’t cycled power, try this yourself; there are some conditions that only cycling the power will clear. Leave the terminal off for about 10 seconds to allow the internal capacitors to discharge completely.

• Next, go to another terminal and try to kill the program that was running on the hung terminal. It may be that the program—and not the terminal—is hung. ...