First of all, ensure Magic SysRq is enabled:
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
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 calls
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.