First of all, ensure Magic SysRq is enabled:

$ cat /proc/sys/kernel/sysrq

0 means “disabled”, 1 means “everything enabled” and >1 is a bitmask of allowed keys. If you are using Ubuntu, you can modify the `/etc/sysctl.d/10-magic-sysrq.conf` file to set this value at boot time.

You invoke SysRq by hitting “Alt + SysRq + Key” on your keyboard. If you can’t find the “SysRq” key on your keyboard, it is usually the same as the “Print Screen” key.

If your Linux computer is acting crazy and you want to safely reboot it, this is the mnemonic to remember: “Raising Elephants Is So Utterly Boring”:

  • R: unRaw (take control of the keyboard back from X)
  • E: tErminate (send SIGTERM to all processes)
  • I: kIll (send SIGKILL to all processes except init)
  • S: Sync (flush filesystem buffers)
  • U: Unmount (remount all filesystems read-only)
  • B: reBoot

Another good key to keep in mind is ‘f’. This call `oom_kill()` which finds and kills a “big” process in order to give back some RAM to your system. If your system is slowing to a crawl, this is something that can save your skin.

More information here.

I work as a freelancer, so if you don’t want to do that kind of things yourself or don’t have the time, just drop me a line to hire me.