Recovering from Linux freezes with “Raising Skinny Elephants Is Utterly Boring”

04 Jun 2009 3 Comments

In the rare cases that a Linux machine freezes, it can usually be rebooted with the Ctrl-Alt-Backspace key combination. However, if this doesn’t work you can try raising the elephant:

To be able to use this functionality, your kernel needs to be compiled with the CONFIG_MAGIC_SYSRQ option on. If your kernel was compiled with this option, entering the following command on the command line should cause the same path to be echoed out:

ls /proc/sys/kernel/sysrq

A simple mnemonic to remember the combination of keys to raise the elephant is “Raising Skinny Elephants Is Utterly Boring” (RSEIUB). Hold down the left Alt and the SysRq (sometimes labelled “Print Screen“) keys and press the following letters in this order, making sure that you give a few seconds pause between keystrokes:

  • R – put keyboard in raw mode
  • S – sync the disk
  • E – terminate all processes
  • I – kill all processes
  • U – remount all filesystems read-only
  • B – reboot the system

If your system uses an ext3 or ReiserFS filesystem and it requests to do a filesystem check while rebooting, you should let it automatically recover the journal by not pressing any key when you are prompted to press “Y“.

 

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3 Responses to “Recovering from Linux freezes with “Raising Skinny Elephants Is Utterly Boring””

  1. Custom Distros Reply 05 Jun 2009 at 03:30

    This looks quite interesting. I’ve never tried anything outside of CTRL + ALT + Backspace before. Might have to see about adding this to my setup.

  2. Warren Reply 06 Feb 2010 at 03:38

    > …Hold down the left Alt and the SysRq (sometimes
    > labelled “Print Screen“) keys and press the
    > following letters in this order…

    Press [ALT][SYSREQ] and release or continue holding them while you press the other keys?

    Sounds like one might need a 3rd appendage…if you don’t already have one. :)

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