What to Do If a System Hangs

A system may freeze or hang rather than crash completely if some software process is stuck. Follow these steps to recover from a hung system.

1. Determine whether the system is running a window environment and follow the suggestions listed below. If these suggestions don't solve the problem, go to step 2.

   • Make sure the pointer is in the window where you are typing the commands

   • Press Control-q in case the user accidently pressed Control-s, which freezes the screen. Control-s freezes only the window, not the entire screen. If a window is frozen, try using another window.

   • If possible, log in remotely from another system on the network. Use the ps command to look for the hung process. If it looks like the window system is hung, identify the process and kill it.

2. Press Control-\ to force a "quit" in the running program and (probably) write out a core file.

3. Press Control-c to interrupt the program that may be running.

4. Log in remotely and attempt to identify and kill the process that is hanging the system.

5. Log in remotely, become superuser and reboot the system.

6. If the system still does not respond, force a crash dump and reboot. See Chapter 69, Generating and Saving System Crash Information for information on forcing a crash dump and booting.

7. If the system still does not respond, turn the power off, wait a minute or so, then turn the power back on.

8. If you cannot get the system to respond at all, contact your local service provider for help.