Sysreq

De whats Wiki

x86 ALT-SYSRQ-[command key] SPARC ALT-STOP-[command key] PowerPC ALT-Print Screen-[command key]

The command keys are as follows: s Attempts to sync all mounted file systems u Attempts to remount all mounted file systems to read-only b Attempts to immediately reboot your system (This is effectively like hitting the reset switch or power button on your box; processes will not be given the chance to shut down.) p Prints the current set of registers and flags to the console t Prints the list of current tasks and related information to the console e Sends a SIGTERM to all processes, with the exception of init i Sends a SIGKILL to all processes, with the exception of init l Sends a SIGKILL to all processes

http://www-106.ibm.com/developerworks/linux/library/l-magic.html