Halting a Hung System

If a system is hung, and commands cannot be entered into a shell on the console, then the key combination STOP-A can be used to halt the system and access the OpenBoot PROM monitor.

Caution  

If the system is halted and rebooted in this way, all data that has not been written to disk will be lost, unless the go command is used to resume the system s normal operation.

An alternative method of accessing a system if the console is locked is to telnet to the system as an unprivileged user , using the su command to obtain superuser status, and kill whatever process is hanging the system. Normal operation can then be resumed.