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Getting out of lockups - SysRq key.See it on your keyboard?!
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jago25_98
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Joined: 23 Aug 2002
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PostPosted: Wed Jul 23, 2003 12:06 am    Post subject: Getting out of lockups - SysRq key.See it on your keyboard?! Reply with quote

Assuming you have in your kernel - Kernel Hacking :: Magic SysRq Key
compiled in...

Gentoo gives you the chance to use unstable everything, especially those gaming kernels with experimental modules, so this can be useful.

To get out of some lock ups you can use the system rescue key.

It's on your keyboard, honest.

Found it?

Ok, it doubles as the print screen key.

To use it hold alt+sysRq+ ->

R (raw)
S ?
E (kill current process, very useful)
I ?
U (unmount mounted filesystems to avoid damage)
B (force reboot)

To remember that sequence - "Raising Silly Elephants Is Utterly Boring"

Reply highlights:

K: Kills all processes in current VC.
R: unRaw keyboard
S - syncs all filesystem (i believe this means that all pending changes are written to the disc).

E - sends SIGTERM to processess.
I - sends SIGKILL to finish of the remaining stubborn processes.


Last edited by jago25_98 on Tue Dec 14, 2004 11:12 am; edited 1 time in total
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jeffrice
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Joined: 25 Jun 2003
Posts: 89
Location: New York, USA

PostPosted: Wed Jul 23, 2003 12:42 am    Post subject: Re: Getting out of lockups - SysRq key.See it on your keyboa Reply with quote

jago25_98 wrote:
Assuming you have in your kernel - Kernel Hacking :: Magic SysRq Key
compiled in...

Gentoo gives you the chance to use unstable everything, especially those gaming kernels with experimental modules, so this can be useful.

To get out of some lock ups you can use the system rescue key.

It's on your keyboard, honest.

Found it?

Ok, it doubles as the print screen key.

To use it hold alt+sysRq+ ->

R (raw)
S ?
E (kill current process, very useful)
I ?
U (unmount mounted filesystems to avoid damage)
B (force reboot)

To remember that sequence - "Raising Silly Elephants Is Utterly Boring"


Woah... you just blew my mind. I'm gonna have to try that... if only I get could my machine to lockup. ppppt.
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Garbz
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Joined: 02 Jul 2003
Posts: 260
Location: Brisbane, Australia

PostPosted: Thu Jul 24, 2003 11:09 am    Post subject: Reply with quote

that is mad i love that.

Judging by what the RSEIUB keys do it appears to very similar to a normal shutdown procedure.

Also from the documentation:

S - syncs all filesystem (i believe this means that all pending changes are written to the disc).

E - sends SIGTERM to processess.
I - sends SIGKILL to finish of the remaining stubborn processes.


All in all it's a great way to get a to reboot a locked system without any filesystem problesm

With that said RSEI is a will drop you to a login screen which will allow you to login with nothin running except a few proceeses started by init. i.e. the gettys, devfsd, and kernel level programs like kapmd kswapd kupdated kreiserfsd and a few others.

At this leve ths sytem is useable. But any programs in the default run level will most likely need to be manually restarted because the system still thinks they are running.

Some options are to "rc boot" and "rc default" but this will generate errors and some services will still not restart. the other option is "for i in /etc/runlevels/boot/*; do /etc/runlevels/boot/$i restart; done

But this will also generate errors.

Any other input is appreciated.
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shash
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Joined: 18 Apr 2003
Posts: 220
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PostPosted: Tue Dec 14, 2004 12:56 am    Post subject: Reply with quote

K: Kills all processes in current VC.
R: unRaw keyboard.

And H (or for that matter, any unrecognized key) will show you all possible combos. Remember, it's the capitalized one there. :)
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Xamindar
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Joined: 03 Oct 2004
Posts: 1155
Location: California

PostPosted: Tue Dec 14, 2004 1:01 am    Post subject: Reply with quote

This is amazing! I'll have to try that when I get home. It's like you just discovered the Roman Empire!
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Garbz
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Location: Brisbane, Australia

PostPosted: Tue Dec 14, 2004 1:33 am    Post subject: Reply with quote

8O 1 Year and six months. A new record of necromancy :lol:
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