SysRq, The magic key

This key is rather useful for linux kernel developers, it enable you to communicate with the kernel regardless of what else it is doing.

This key can be enabled via the CONFIG_MAGIC_SYSRQ (Kernel hacking –> Magic SysRq key), and you need to turn on this option with below command:

echo 1 > /proc/sys/kernel/sysrq

Key Command Description

SysRq-b                Reboot the machine.

SysRq-e                Send a SIGTERM to all processes except init.

SysRq-h                Display SysRq help on the console.

SysRq-i                 Send a SIGKILL to all processes except init.

SysRq-k                Secure Access Key: Kill all programs on this console.

SysRq-l                 Send a SIGKILL to all processes including init.

SysRq-m               Dump memory information to console.

SysRq-o                Shutdown the machine.

SysRq-p                Dump register to console.

SysRq-r                 Turn off keyboard raw mode.

SysRq-s                 Sync all mounted file systems to disk.

SysRq-t                 Dump task information to console.

SysRq-u                Unmount all mounted file systems.