GNU/Linux: Emergency Restart

#1

Post by nicolasbrailo » Tue, May 18, 2010, 2:02 PM UTC

GNU/Linux: Emergency Restart
nicolasb.com.ar

Re: GNU/Linux: Emergency Restart

#2

Post by code_duck » Tue, May 18, 2010, 3:05 PM UTC

This can be handy, no doubt. I have a monitor that flips out blinking if you knock the cord, which my cat has seen fit to do a couple of times.

Don't forget the mnemonic - Raising Elephants Is So Utterly Boring.

There are a couple of variations:

REISUO will shutdown rather than reboot.

Some prefer RSEIUB, syncing earlier in the process - aka Rasing Skinny Elephants Is Unusually Bland. You may wish to throw another Sync in there to make RSEISUB.

Re: GNU/Linux: Emergency Restart

#3

Post by [deleted] » Tue, May 18, 2010, 3:23 PM UTC

[deleted]

Re: GNU/Linux: Emergency Restart

#4

Post by yigit » Tue, May 18, 2010, 3:43 PM UTC

most easy way of remembering is : BUSIER, only backwards.

Re: GNU/Linux: Emergency Restart

#5

Post by [deleted] » Tue, May 18, 2010, 3:46 PM UTC

[deleted]

Re: GNU/Linux: Emergency Restart

#6

Post by nicolasbrailo » Tue, May 18, 2010, 3:47 PM UTC

[deleted] wrote: post #3

[deleted]

The order of the keys is really not that important but the order of the functions each one performs indeed matters. Usually you don't wan't to reboot before you sync :P

Re: GNU/Linux: Emergency Restart

#7

Post by johnswamps » Tue, May 18, 2010, 4:15 PM UTC

It's usually worth trying to ssh into the machine when X locks up (if you don't want to just reboot). Depending on what caused the problem, this will often still work even when it's unresponsive locally.

Re: GNU/Linux: Emergency Restart

#8

Post by Jach » Tue, May 18, 2010, 4:57 PM UTC

code_duck wrote: post #2

This can be handy, no doubt. I have a monitor that flips out blinking if you knock the cord, which my cat has seen fit to do a couple of times. Don't forget the mnemonic - Raising Elephants Is So Utterly Boring. There are a couple of variations: REISUO will shutdown rather than reboot. Some prefer RSEIUB, syncing earlier in the process - aka Rasing Skinny Elephants Is Unusually Bland. You may wish to throw another Sy…

I still prefer the mnemonic "Reboot Even If System Utterly Broken", plus it describes what it does. :)

Re: GNU/Linux: Emergency Restart

#9

Post by bcl » Tue, May 18, 2010, 5:26 PM UTC

IIRC the kernel needs to be compiled with the magic sysreq keys enabled, so if this doesn't work for you you will likely need to rebuild your kernel. Or grow a couple extra digits.

Re: GNU/Linux: Emergency Restart

#10

Post by cnvogel » Tue, May 18, 2010, 6:01 PM UTC

Further information about how and what to trigger things with the Magic-Sysrq-Key is documented in $KERNEL/Documentation/sysrq.txt, which you can access for example in Linus' GIT tree at...

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6...

One very useful function, for example, is to force a hard reboot when ssh'ed into a server:

echo b >/proc/sysrq-trigger