Shortcut Keys – Alt + Sysrq + REISUB Doesn’t Reboot Laptop

rebootshortcut-keyssysrq

On occasion, my laptop has become stuck so I've used the magic key combination of Alt + SysRq + REISUB to perform a safe reboot. However, it doesn't seem to work for me as when I press the B key to complete the magic key command it simply says, "resetting…" and doesn't do anything.

All of the other keys seem to work fine as it resets the keyboard layout, kills all tasks etc., but it doesn't seem to complete with a reboot.

I was under the impression that my laptop should reboot after the magic keys have all been pressed in the order of REISUB.

Best Answer

Alt+SysRq has been disabled to fix a bug. The disabling of Magic-SysRq was considered a bug itself and it has since been re-enabled (#1025467). If it is still disabled for you, you can re-enable it:

Ubuntu 12.04 and older

Edit the file /etc/sysctl.conf to include the line

kernel.sysrq=1

Ubuntu 12.10 and newer

Starting with Ubuntu 12.10 a more fine-grained control of which Magic-SysRq features are enabled is possible. Just edit the file /etc/sysctl.d/10-magic-sysrq.conf.

The file is well documented and tells you exactly how to enable which features. The current default was picked for security purposes and should only be changed if you know why you need to (for security implications see #194676).

Related Solutions

Ubuntu – ALT+SysRq+REISUB hangs at “resetting” (without actually resetting/restarting)

Alt + SysRq +

R - takes keyboard and mouse control from the X server. This can be useful if the X-Server crashed, you can change to a console and kill the X-Server or check the error log. NOTE:- The documentation refers to this key's task as "Turns off keyboard raw mode and sets it to XLATE", but I suppose it's safe enough to assume that it takes back control from X.

E - sends SIGTERM to all processes except init. This means that an attempt is done to end the current processes except init, safely, e.g. saving a document.

I - sends SIGKILL to all processes except init. This means that all the processes except for init are killed, any data in processes that are killed will be lost.

S - writes all data from the disc cache to the hard-discs, it is a sync and is necessary to reduce the chances of data corruption.

U - remounts all mounted filesystems read-only. After using this key, you can reboot the system with Alt+SysRq+B without harming the system.

B - restarts the system without making steps to ensure that the conditions are good for a safe reboot, using this key alone is like doing a cold reboot.

Try without pressing R at begining of your sequence or just do it in another seq.. give a litle time between those keystrokes and do this..

Alt + SysRq + R S E I U B

and better you enable Magic SysRq by entering..

echo 1 > /proc/sys/kernel/sysrq

shortcut-keys – Get Alt+SysRq Working on Dell Latitude E6530

The Dell E6420 works as follows

Press/hold both Fn and Alt
Press/hold Home/Sysrq
Release Fn
Press key (tested with T)