How to recover from a Frozen System

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Re: How to recover from a Frozen System

Postby z06gal on Tue Dec 27, 2011 7:35 pm

rdanner3 wrote:What's funny is that I accidentally used KISUB once, and it worked. Now, if the GUI locks, I just Alt-PrtScr + K and it restarts.

The Wikipedia article is pretty informative and gives functions I had no idea of that could be quite useful, too.



Mine froze yesterday and the REISUB did nothing. Next time I'll try what you did and see what happens :wink:
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Re: How to recover from a Frozen System

Postby j0x on Wed Mar 07, 2012 10:08 pm

jxgreat wrote:Well good.
But while completing typing it unmounted all the drives and terminated the tasks but it doesn't restart my computer. I have to manually press the power button to shutdown it.


well in my case i have to press an additional key combos of CTRL+ALT+DELETE to restart Linux Mint

or is their anything we are missing or doing wrong? i like to know, any experts reading please let us know :)
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Re: How to recover from a Frozen System

Postby Thinker on Wed Apr 25, 2012 4:52 am

Is this recovery? All data will be lost. This is of no use for a common user. "Safe way to restart" is better name for this article.

Presing Alt+Print Scr + K will cause logout by Killing X-server. Although this will not save any data but it is much better and time saving than REISUB
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Re: How to recover from a Frozen System

Postby ElMugroso on Sat May 05, 2012 3:28 am

Does it matter upper or lower case in REISUB?
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Re: How to recover from a Frozen System

Postby rdanner3 on Sat Jun 09, 2012 12:07 am

ElMugroso wrote:Does it matter upper or lower case in REISUB?
No. But you must hold down ALT and PrtScn (also labeled SysReq on some keyboards) throughout. That's why it takes both hands to successfully use.

ALT+PrtScrn+B should shut down the system. Do not recall the letter to restart.

Incidentally, if you happen to be in a terminal while using the magic-key combos, you might well see some statements fly by. Or you might not. It seems to be a tad random, at least in my experience.
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Re: How to recover from a Frozen System

Postby donec on Sun Jun 17, 2012 2:08 pm

Why can't this problem be fixed?

I have had this happen on 3 different computers with LM 10, LM 11 and LM 12. Still no fix?

This is almost like the Blue Screen of Death except it doesn't give a code that can't be understood.
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Re: How to recover from a Frozen System

Postby Absolutis on Mon Jun 18, 2012 7:54 am

Great trick. But does it work on mac keyboards, with f14, f15, f16 instead of print screen, scroll lock and pause/break?
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Re: How to recover from a Frozen System

Postby spacer on Tue Jul 24, 2012 6:09 pm

D'oh! I pressed ctrl+alt+backspace to see what it did while i was updating my computer. I thought it was gonna open up system monitor or something
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Re: How to recover from a Frozen System

Postby rdanner3 on Thu Aug 02, 2012 2:14 am

Thinker wrote:Is this recovery? All data will be lost. This is of no use for a common user. "Safe way to restart" is better name for this article.
Tend to agree here.

Thinker wrote:Pressing Alt+Print Scr + K will cause logout by Killing X-server. Although this will not save any data but it is much better and time saving than REISUB
Also note that CTRL-ALT+BKSP will also do that. Have had both fail, though, forcing use of REISUB anyway. (BTW: REISUO will (IIRC) shut the machine off, not restart. Sometimes, if you're just this side of throwing the machine out the window, that might be the wiser choice.)
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Re: How to recover from a Frozen System

Postby Shredded on Thu May 23, 2013 11:03 am

Thank you, i force restarted the pc yesterday and it completely broke ny mint. Definitely saving this on my tablet.
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Re: How to recover from a Frozen System

Postby SilverNexus on Fri Jul 26, 2013 6:39 pm

Used this handy trick to restart my computer when Banshee froze my whole computer upon me unmounting a USB disk (I haven't recreated it yet, so I'll not create a post for this issue). I probably could have gotten away with killing X server, but I had Ctrl-Alt-Bksp disabled (as is default), so along came this shutdown method. Worked like a charm, I must say.
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Re: How to recover from a Frozen System

Postby deminted on Sun Jan 19, 2014 12:08 am

I see this is rather an old post, but I thought it might save some people puzzlement & angst if I add an update.

Firstly
NOTE: for 'magic keys', recent versions of Mint no longer use SysRq with Alt (left), they use: SysRq with Alt (right) plus whatever (lower case)

A while back, some joker decided to disable the 'magic keys' by default, preventing orderly recovery in a stuck emergency.
I have no idea what the logic of this was, if any. What would I know? Probably a very wise person.
I expect there's a discussion somewhere saying how uttrerly pointless it would be to disable these key features by default if someone is going to have access to the main keyboard anyway, but no doubt there are other wiser views prevailing.

One doesn't really notice until one gets into problems, and finds sysrq-ralt isn't available, then starts muttering curses.

When I start a new system I use the following steps to inject some common sense.
(Just after going to System Settings > Regional settings > options > set 'sequence to kill X-server' , presumably disbabled by default by the same wiseperson)

Maybe not the most elegant way, but it works for me.

enable the whole idea:
Code: Select all
echo 1 | sudo tee /proc/sys/kernel/sysrq


which one might think was enough, but it seems one must also edit /etc/sysctl.d

use file manager nemo, go to 'Filesystem' then select /etc/sysctl.d
(or Filesystem > /etc > sysctl.d ... heading there directly from /home/mint seems not to work)

right-click, [open as root]

use gedit to edit 10-magic-sysrq.conf
change the last line from " kernel.sysrq = 176 " (which disables all the useful emergency commands)
to
Code: Select all
# kernel.sysrq = 176
kernel.sysrq = 1


Now the 'magic keys ' will work when you need them.

(Remember to close the priviledged panels before something silly happens.)

If you use magic commands from a terminal screen ( ctl+alt+F2, say), you will see them respond. Some give interesting if not useful info.
Some are pretty weird and seem to take for ever, or flood the console (not useful!), but SysRq+Alt(rt)+ r e i s u b (typed in slowly with circumspection) often allows an orderly stop & reboot.
It will not work if there is kernel panic.
In a 'live' system, it will ensure that most files are 'sync'd to disc before stopping (if one waits or that to complete), but it will not restart one's live system as tinkered-with; instead it will take you back to a new live install base menu so you can start all over again. Oh, joy.

to quote WikiPedia http://en.wikipedia.org/wiki/Magic_SysRq_key
...unraw (take control of keyboard back from X),
.... terminate (send SIGTERM to all processes, allowing them to terminate gracefully),
.. ..kill (send SIGKILL to all processes, forcing them to terminate immediately),
......sync (flush data to disk),
_ _ _ _ _ wait!
......unmount (remount all filesystems read-only),
....reboot

I hope that's helpful.

If someone has a better way (especially with regard to a live system), I would be interested to hear it.
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