Wednesday, January 16, 2008

Rebooting linux without reboot command

Just a sample of how you can reboot or shutdown linux without issuing reboot command, so called hard reboot. That means that system will just make a reset as if you pressed a reset button, without running any shutdown scripts, etc. A kind of dangerous staff, but can be helpful in some occasions.

echo 1 > /proc/sys/kernel/sysrq 
echo b > /proc/sysrq-trigger
If you want to force shutdown machine try this.

echo 1 > /proc/sys/kernel/sysrq
echo o > /proc/sysrq-trigger


Unknown said...

Don't forget to run sync before hard rebooting.
Or if you want 2 b h4ck3r again:
echo s > /proc/sysrq-trigger

Urgentissimo! said...

Great one!

I had "I/O errors" on a hard disk of a remote server but was still able to enter via ssh (almost any command failed with "disk I/O error").

After dumping the dmesg (that shows me some HDD Flush Cache failure) I was able to reboot using those two commands.

Pete said...

I always remember it as "busier" spelled backwards.
r - reset tty
e - exit all processes
i - kill all processes
s - sync hdd
u - unmount all hdd
b - reboot
That's using the actual alt-sysreq-? keys at the console, though. If you sent e or i to the proc via cli, you'd end your cli session...