Forcing a Linux Reboot

Linux zfs-fuse is an extremely useful piece of software, but this morning it crashed on me to the point where even 'reboot -f' was failing to reboot the server due to kernel confusion.

Fortunately, there is a way to use the Linux SysRq mechanism to force an immediate reboot. This won't sync the disks, and certainly won't wait for processes to terminate (which is why it works in this case), but it certainly saved me from going to the data center to manually intervene.

To do an emergency reboot on Linux, perform the following two steps as root:

echo 1 > /proc/sys/kernel/sysrq

echo b > /proc/sysrq-trigger

This causes an immediate reboot of the system. Of course, if the thing causing the problem was a corrupted root filesystem, the server may not boot, but that would be the case regardless :-)

More details on SysRq are available at the Linux Kernel site.