[ubuntu-uk] Server shutting itself down or going into a deep sleep

[Johnathon Tinsley]

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>> <snip>
>> Have you tried using the Magic SysRq key on the keyboard?
>> ...
>> The meanings of the keys, IIRC:
>> R - raw keyboard mode (stop X grabbing the key presses)
>> E - send SIGTERM to all processes
>> I - send SIGTERM to init
>> S - sync the disks
>> U - unmount the mounted partitions
>> B - reboot
> 
> It's probably worth mentioning that you need to wait a second or 2 
> between each key press. If you do it too quickly I have noticed it 
> doesn't always work.
> 

Almost got all the meanings.
I sends SIGKILL to all processes, killing anything that hasn't yet
terminated itself. You should wait at least 5-10 seconds after hitting
'e' to hit 'i', because it's effectively kill -9, so will stop all
processes without letting them gracefully stop.
(In fact, it sends SIGKILL to everything *but* init :-) )

U doesn't just un-mount the partitions, it remounts them read-only.
Useful if you need to quickly stop writes hitting a corrupted disk, but
don't want to take the system offline!

And no, you don't need to take your fingers off of the ALT + SYSRQ keys
every time you hit a letter. Many a time have I used "raising elephants
is so" at 3am at our datacentre ;)

Johnathon
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