Ubuntu – Alt + sysrq + REISUB doesn’t reboot the laptop


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


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).