Magic Linux Reboot
What if your Linux system hangs in between ? Your keyboard stops responding, mouse stops moving, programs freezed. Most of you will think of unplugging your PC or force shutdown it using the Power button. That results in lot of troubles. Your hard disk may crash and lead to other such troubles also because so many processes would be working behind and they will suddenly go to a halt. Well if you have such a situation, which is rare only in some cases and that too because of hardware compatibility in Linux, Linux Kernel inbuilt feature REISUB provides you a wonderful magic linux restart.
This feature is inbuilt in the linux kernel, so it common to all linux distributions. Whenever you feel that your PC is hanged, and you have no choice except shutting your system down forcefully, you can try this last resort.
SysRq key ?
You need to find the Magic SysRq key in your keyboard. In some systems you have this key with the name SysRq but in other systems, this key can be activated by pressing Fn with PrintScr key. A combination of both Fn and PrintScr produces the effect of SysRq key.
Press the Alt key and hold it. Now Press the sysRq key ( either directly or indirectly if you don't have a sysRq key in your keyboard as mentioned above). Now while holding Alt + sysRq (Alt + fn + sysRq) type the following letters slowly, to reboot your system:
R E I S U B
On pressing B , your system will reboot.
Or else try this, to shutdown your system safely:
R E I S U O
On pressing O, your system will shutdown safely.
All those sequence of keys before that do the following tasks :
R: Take the control of keyboard back from the Window manager. E: Send the SIGTERM signal to all processes except init I: Send the SIGKILL signal to all processes except init S: Sync all mounted filesystems U: Remount all mounted filesystems in read-only mode B: Immediately reboot the system, without unmounting partitions or syncing. O: Shutdown the system.
After this your system should successfully restart itself. There are other combinations also like this that does almost the same but in a slightly different manner.