2:55 p.m.
It is hard to know where to start with the problems with the use of the
SysReg key.. Since acording to the Wikipedia notes in order to get these
Magic SysReg features to work you have tp add the Ctrl button. So to
reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
workstation Keyboard this is nearly impossible to do because of the
position of the SysReg key in the upper right corner of the keyboard.
On my laptop where I can hit the keys the function fails to work.
Without the Ctrl all you get is screen shots which I do get.
With the alternate approach of:
echo key > /proc/sysreq-trigger the reboot works but I can't detect
anything else working.
So how does one use these magic keys ?
--
=======================================================================
You have a deep appreciation of the arts and music.
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
11:52 a.m.
On 08/22/2012 06:20 AM, Aaron Konstam uttered this comment:
On Wed, 2012-08-22 at 22:32 +0930, Tim wrote:
> On Tue, 2012-08-21 at 15:27 -0500, Aaron Konstam wrote:
>> Theree seems to be general agreement if you don't include the CTRL key
>> only a snapshopt is genrqated the function is not executed.
>
> Depends on your user interface... If you're using something like Gnome,
> it's assigned its own function to ALT and PrintScreen (to screengrab the
> current active window), versus PrintScreen (by itself, to screengrab the
> whole desktop).
>
> Whereas, at a basic text-only console, it may be ignoring presses of the
> PrintScreen/SystemRequest key, and pass it along, for something else to
> deal with.
>
> The same goes for other hotkeys. Outside of Gnome, for instance, you
> can switch between terminals simply by pressing ALT and one of the
> Function keys. Inside Gnome, it's using those key combinations for its
> own purposes, so another key sequence is used. Again, adding CTRL to
> it, does the job.
>
I did all these things in a alt-f2 console (no Gnome). And they still
did not work. I want some one to tell me they hit: cntl+alr+sysrq b and
got a reboot.
Running F17/x86_64, fully updated, XFCE/xwfm4 on my Dell N7110 laptop:
1. echo "1" >/proc/sys/kernel/sysrq
2. CTRL+ALT+F2 to get a text console
3. Logged in as root
4. LEFT-ALT+PRSCR+"b" = reboot
To reiterate, that was the left ALT key.
So it works for me, Aaron.
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, AllDigital ricks(a)alldigital.com -
- AIM/Skype: therps2 ICQ: 22643734 Yahoo: origrps2 -
- -
- Change is inevitable, except from a vending machine. -
----------------------------------------------------------------------
3:36 p.m.
On 08/20/2012 01:24 PM, Aaron Konstam wrote:
Ok, it can be reached when you use both hands but it still does not
work
for me. Does it matter which Ctrl key you use?
I've always used the left one.
Just to be clear, in /etc/sysctl.conf I changed: kernel.sysrq to 1
from
0.
If you've rebooted since doing that, you've turned it off.
4:48 p.m.
On 08/20/2012 02:27 PM, Aaron Konstam uttered this comment:
On Mon, 2012-08-20 at 13:20 -0700, Rick Stevens wrote:
> On 08/20/2012 01:05 PM, Joe Zeff uttered this comment:
>> On 08/20/2012 12:55 PM, Aaron Konstam wrote:
>>> It is hard to know where to start with the problems with the use of the
>>> SysReg key.. Since acording to the Wikipedia notes in order to get these
>>> Magic SysReg features to work you have tp add the Ctrl button. So to
>>> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
>>> workstation Keyboard this is nearly impossible to do because of the
>>> position of the SysReg key in the upper right corner of the keyboard.
>>> On my laptop where I can hit the keys the function fails to work.
>>> Without the Ctrl all you get is screen shots which I do get.
>>>
>>> With the alternate approach of:
>>> echo key > /proc/sysreq-trigger the reboot works but I can't detect
>>> anything else working.
>>>
>>> So how does one use these magic keys ?
>>>
>>
>> I can't speak for anybody else, but when I've experimented with it, I
>> used both hands.
>
> It's supposed to be a simultaneous press of ALT, SYSRQ (or PRINTSCREEN)
> and the command key (B in your case). Note it only works if
> /proc/sys/kernel/sysrq contains a non-zero value. To enable ALL
> functionality, first set /proc/sys/kernel/sysrq to the value "1":
>
> echo "1" >/proc/sys/kernel/sysrq
>
> Then hit your key combo. Some keyboards may have issues with so many
> simultaneous keypresses. In those cases hold down ALT, then press and
> release SYSRQ, then press and release your command key and finally
> release ALT.
>
> It's been a while since I futzed with it. If you have the kernel-doc
> RPM installed, it's explained in
>
> /usr/share/doc/kernel-doc-(version)/Documentation/sysrq.txt
I appreciate all these tips but none make the sysrq suctions work. I'll
just give up.
Worked for me on my Dell laptop. Process:
1. Did 'echo "1" >/proc/sys/kernel/sysrq'
2. Held down left-ALT, held down PRNTSCR, pressed "h"
3. Released all three keys
4. Ran "dmesg" and saw this:
[111065.967134] SysRq : HELP : loglevel(0-9) reBoot Crash
terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I)
thaw-filesystems(J) saK show-backtrace-all-active-cpus(L)
show-memory-usage(M) nice-all-RT-tasks(N) powerOff show-registers(P)
show-all-timers(Q) unRaw Sync show-task-states(T) Unmount force-fb(V)
show-blocked-tasks(W) dump-ftrace-buffer(Z)
5. Did 'echo "0" >/proc/sys/kernel/sysrq' to disable SYSRQ.
Fully updated F17, 3.5.2-1.fc17.x86_64, XFCE and xfwm4 window manager.
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, AllDigital ricks(a)alldigital.com -
- AIM/Skype: therps2 ICQ: 22643734 Yahoo: origrps2 -
- -
- To err is human. To forgive, a large sum of money is needed. -
----------------------------------------------------------------------
3:30 p.m.
On 20 August 2012 21:29, Hakan Koseoglu <hakan(a)koseoglu.org> wrote:
to do CTRL-ALT-DEL, he fell off laughing when one of his students
held
CTRL using one finger on one hand, ALT using an other finger on the
other hand and then hit the ALT using his nose...
Of course, that should have been,
CTRL, DEL and ALT in that order.
Idiot me. :) Can't even tell a story straight.
2:39 p.m.
On 08/22/2012 06:26 AM, Reindl Harald wrote:
i explained you in my last mail that CTRL+ALT+PRINT+B is plain
stoopid, so nobody will do this - i CONFIRMED multiple
times that STRG+ALT+PRINT+S does a sync, i hear the drives and
i get messages in dmesg, /var/log/messages AND also in a ALT-F2
console independent if there is a login or not, if there is the
login-prompt i get
SysRq : Emergency Sync
Emergency Sync complete
directly below the prompt
That's exactly what I saw when I tried it. I've never tried following
it with b, except when (as it turned out) the system wasn't responding
to anything, but maybe I will next time I need to reboot anyway.
12:25 p.m.
On Wed, Aug 22, 2012 at 03:17:30PM +0200, Reindl Harald wrote:
Am 22.08.2012 15:13, schrieb Aaron Konstam:
> Well please try b and let me know if the reboot occurs. The problem is b
> is the only one where the results are obvious. I am willing to believe
> that people see the output in dmesg or /var/log/messages, but they don't
> really know if the action is executed.
sure
S: you hear the emegency.sync on a RAID10 device
K: i see that if KDE freezes a come back to Login
B: you SHOULD NEVER use it alone because you could also use hardware-reset
posted many times but nobody reads docs people telling:
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),
Unmount (remount all filesystems read-only),
reBoot.
Hold down the Alt and SysRq (Print Screen) keys.
While holding those down, type the following keys in order, several seconds apart:
REISUB
Computer should reboot.
A mnemonic that helps me remember the above is that REISUB spells
BUSIER, backwards.
--
---- Fred Smith -- fredex(a)fcshome.stoneham.ma.us -----------------------------
"Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of
heaven, but only he who does the will of my Father who is in heaven."
------------------------------ Matthew 7:21 (niv) -----------------------------
5:05 p.m.
On 08/22/2012 02:17 PM, jdow wrote:
Even with the reminders I've seen people keep forgetting that
most
modern keyboards are two key roll-over keyboards. The keys are matrix
scanned in a fashion that any two keys pressed at the same time can
be detected but more than two keys pressed at the same time is very
iffy. You guys may be fighting an inherent keyboard problem rather
than an OS deficiency.
That may be why some of the instructions for this call for pressing
Alt-SysRq (pause) Command, and why I've had best luck with pressing the
keys one at a time and holding them down until all are pressed.
4:17 p.m.
On 2012/08/22 06:02, Tim wrote:
On Tue, 2012-08-21 at 15:27 -0500, Aaron Konstam wrote:
> Theree seems to be general agreement if you don't include the CTRL key
> only a snapshopt is genrqated the function is not executed.
Depends on your user interface... If you're using something like Gnome,
it's assigned its own function to ALT and PrintScreen (to screengrab the
current active window), versus PrintScreen (by itself, to screengrab the
whole desktop).
Whereas, at a basic text-only console, it may be ignoring presses of the
PrintScreen/SystemRequest key, and pass it along, for something else to
deal with.
The same goes for other hotkeys. Outside of Gnome, for instance, you
can switch between terminals simply by pressing ALT and one of the
Function keys. Inside Gnome, it's using those key combinations for its
own purposes, so another key sequence is used. Again, adding CTRL to
it, does the job.
Even with the reminders I've seen people keep forgetting that most
modern keyboards are two key roll-over keyboards. The keys are matrix
scanned in a fashion that any two keys pressed at the same time can
be detected but more than two keys pressed at the same time is very
iffy. You guys may be fighting an inherent keyboard problem rather
than an OS deficiency.
I have an animatronics programming application that can use the number
keys on a keyboard for controlling the actions of selected channels of
the animations. I had to find a true N-Key rollover keyboard to prove
it actually worked as advertised with a proper keyboard. Erm, that
keyboard was a gaming keyboard from <gisp> Microsoft, in case anybody
is wondering.
{^_^}
3:38 p.m.
On 08/21/2012 01:27 PM, Aaron Konstam wrote:
First everyone seems to agree that it is the ALT button on the right
that needs to be used Theree seems to be general agreement if you don't
include the CTRL key only a snapshopt is genrqated the function is not
executed. I got the same output as you did but when I uswed b instead of
h I goot output about a reboot but it did not occur..
I've found that if I add Ctrl, I can use either Alt key, and that
pressing them sequentially, but not letting go until all are pressed
works best for me. I've not, as yet, tried using b.
8:26 a.m.
Am 22.08.2012 15:20, schrieb Aaron Konstam:
On Wed, 2012-08-22 at 22:32 +0930, Tim wrote:
> On Tue, 2012-08-21 at 15:27 -0500, Aaron Konstam wrote:
>> Theree seems to be general agreement if you don't include the CTRL key
>> only a snapshopt is genrqated the function is not executed.
>
> Depends on your user interface... If you're using something like Gnome,
> it's assigned its own function to ALT and PrintScreen (to screengrab the
> current active window), versus PrintScreen (by itself, to screengrab the
> whole desktop).
>
> Whereas, at a basic text-only console, it may be ignoring presses of the
> PrintScreen/SystemRequest key, and pass it along, for something else to
> deal with.
>
> The same goes for other hotkeys. Outside of Gnome, for instance, you
> can switch between terminals simply by pressing ALT and one of the
> Function keys. Inside Gnome, it's using those key combinations for its
> own purposes, so another key sequence is used. Again, adding CTRL to
> it, does the job.
>
I did all these things in a alt-f2 console (no Gnome). And they still
did not work. I want some one to tell me they hit: cntl+alr+sysrq b and
got a reboot.
i explained you in my last mail that CTRL+ALT+PRINT+B is plain
stoopid, so nobody will do this - i CONFIRMED multiple
times that STRG+ALT+PRINT+S does a sync, i hear the drives and
i get messages in dmesg, /var/log/messages AND also in a ALT-F2
console independent if there is a login or not, if there is the
login-prompt i get
SysRq : Emergency Sync
Emergency Sync complete
directly below the prompt
8:20 a.m.
On Wed, 2012-08-22 at 22:32 +0930, Tim wrote:
On Tue, 2012-08-21 at 15:27 -0500, Aaron Konstam wrote:
> Theree seems to be general agreement if you don't include the CTRL key
> only a snapshopt is genrqated the function is not executed.
Depends on your user interface... If you're using something like Gnome,
it's assigned its own function to ALT and PrintScreen (to screengrab the
current active window), versus PrintScreen (by itself, to screengrab the
whole desktop).
Whereas, at a basic text-only console, it may be ignoring presses of the
PrintScreen/SystemRequest key, and pass it along, for something else to
deal with.
The same goes for other hotkeys. Outside of Gnome, for instance, you
can switch between terminals simply by pressing ALT and one of the
Function keys. Inside Gnome, it's using those key combinations for its
own purposes, so another key sequence is used. Again, adding CTRL to
it, does the job.
I did all these things in a alt-f2 console (no Gnome). And they still
did not work. I want some one to tell me they hit: cntl+alr+sysrq b and
got a reboot.
--
=======================================================================
It's multiple choice time... What is FORTRAN? a: Between thre and fiv
tran. b: What two computers engage in before they interface. c:
Ridiculous.
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
8:17 a.m.
Am 22.08.2012 15:13, schrieb Aaron Konstam:
Well please try b and let me know if the reboot occurs. The problem
is b
is the only one where the results are obvious. I am willing to believe
that people see the output in dmesg or /var/log/messages, but they don't
really know if the action is executed.
sure
S: you hear the emegency.sync on a RAID10 device
K: i see that if KDE freezes a come back to Login
B: you SHOULD NEVER use it alone because you could also use hardware-reset
posted many times but nobody reads docs people telling:
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),
Unmount (remount all filesystems read-only),
reBoot.
Hold down the Alt and SysRq (Print Screen) keys.
While holding those down, type the following keys in order, several seconds apart:
REISUB
Computer should reboot.
8:15 a.m.
On Wed, 2012-08-22 at 07:46 +0200, Heinz Diehl wrote:
On 22.08.2012, Reindl Harald wrote:
> why should reboot turn it off?
Because he turned off the option in sysctl.conf, and a reboot will
activate it.
Huh, I turned it on not off.
--
=======================================================================
Chicken Little only has to be right once.
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
8:13 a.m.
On Tue, 2012-08-21 at 13:38 -0700, Joe Zeff wrote:
On 08/21/2012 01:27 PM, Aaron Konstam wrote:
> First everyone seems to agree that it is the ALT button on the right
> that needs to be used Theree seems to be general agreement if you don't
> include the CTRL key only a snapshopt is genrqated the function is not
> executed. I got the same output as you did but when I uswed b instead of
> h I goot output about a reboot but it did not occur..
I've found that if I add Ctrl, I can use either Alt key, and that
pressing them sequentially, but not letting go until all are pressed
works best for me. I've not, as yet, tried using b.
Well please try b and let me know if the reboot occurs. The problem is b
is the only one where the results are obvious. I am willing to believe
that people see the output in dmesg or /var/log/messages, but they don't
really know if the action is executed.
--
=======================================================================
If you flaunt it, expect to have it trashed.
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
8:02 a.m.
On Tue, 2012-08-21 at 15:27 -0500, Aaron Konstam wrote:
Theree seems to be general agreement if you don't include the
CTRL key
only a snapshopt is genrqated the function is not executed.
Depends on your user interface... If you're using something like Gnome,
it's assigned its own function to ALT and PrintScreen (to screengrab the
current active window), versus PrintScreen (by itself, to screengrab the
whole desktop).
Whereas, at a basic text-only console, it may be ignoring presses of the
PrintScreen/SystemRequest key, and pass it along, for something else to
deal with.
The same goes for other hotkeys. Outside of Gnome, for instance, you
can switch between terminals simply by pressing ALT and one of the
Function keys. Inside Gnome, it's using those key combinations for its
own purposes, so another key sequence is used. Again, adding CTRL to
it, does the job.
--
[tim@localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686
Don't send private replies to my address, the mailbox is ignored. I
read messages from the public lists.
3:27 p.m.
On Mon, 2012-08-20 at 14:48 -0700, Rick Stevens wrote:
On 08/20/2012 02:27 PM, Aaron Konstam uttered this comment:
> On Mon, 2012-08-20 at 13:20 -0700, Rick Stevens wrote:
>> On 08/20/2012 01:05 PM, Joe Zeff uttered this comment:
>>> On 08/20/2012 12:55 PM, Aaron Konstam wrote:
>>>> It is hard to know where to start with the problems with the use of the
>>>> SysReg key.. Since acording to the Wikipedia notes in order to get
these
>>>> Magic SysReg features to work you have tp add the Ctrl button. So to
>>>> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
>>>> workstation Keyboard this is nearly impossible to do because of the
>>>> position of the SysReg key in the upper right corner of the keyboard.
>>>> On my laptop where I can hit the keys the function fails to work.
>>>> Without the Ctrl all you get is screen shots which I do get.
>>>>
>>>> With the alternate approach of:
>>>> echo key > /proc/sysreq-trigger the reboot works but I can't
detect
>>>> anything else working.
>>>>
>>>> So how does one use these magic keys ?
>>>>
>>>
>>> I can't speak for anybody else, but when I've experimented with it,
I
>>> used both hands.
>>
>> It's supposed to be a simultaneous press of ALT, SYSRQ (or PRINTSCREEN)
>> and the command key (B in your case). Note it only works if
>> /proc/sys/kernel/sysrq contains a non-zero value. To enable ALL
>> functionality, first set /proc/sys/kernel/sysrq to the value "1":
>>
>> echo "1" >/proc/sys/kernel/sysrq
>>
>> Then hit your key combo. Some keyboards may have issues with so many
>> simultaneous keypresses. In those cases hold down ALT, then press and
>> release SYSRQ, then press and release your command key and finally
>> release ALT.
>>
>> It's been a while since I futzed with it. If you have the kernel-doc
>> RPM installed, it's explained in
>>
>> /usr/share/doc/kernel-doc-(version)/Documentation/sysrq.txt
> I appreciate all these tips but none make the sysrq suctions work. I'll
> just give up.
Worked for me on my Dell laptop. Process:
1. Did 'echo "1" >/proc/sys/kernel/sysrq'
2. Held down left-ALT, held down PRNTSCR, pressed "h"
3. Released all three keys
4. Ran "dmesg" and saw this:
[111065.967134] SysRq : HELP : loglevel(0-9) reBoot Crash
terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I)
thaw-filesystems(J) saK show-backtrace-all-active-cpus(L)
show-memory-usage(M) nice-all-RT-tasks(N) powerOff show-registers(P)
show-all-timers(Q) unRaw Sync show-task-states(T) Unmount force-fb(V)
show-blocked-tasks(W) dump-ftrace-buffer(Z)
5. Did 'echo "0" >/proc/sys/kernel/sysrq' to disable SYSRQ.
Fully updated F17, 3.5.2-1.fc17.x86_64, XFCE and xfwm4 window manager.
First everyone seems to agree that it is the ALT button on the right
that needs to be used Theree seems to be general agreement if you don't
include the CTRL key only a snapshopt is genrqated the function is not
executed. I got the same output as you did but when I uswed b instead of
h I goot output about a reboot but it did not occur..
Ther lies the problem. I have 2 Della, a workstation and a laptop and
neither work the way they should.
Whne you use b instead of h do you get a reboot?.
--
=======================================================================
It is not doing the thing we like to do, but liking the thing we have to
do, that makes life blessed. -- Goethe
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
10:19 a.m.
On Tue, 2012-08-21 at 07:55 +0200, Heinz Diehl wrote:
Now press the right ALT key together with PrtScrn...
With qualifier keys, such as CTRL, SHIFT, ALT, which change the
behaviour of other keys (a becomes A, etc.), it's usually best to press
the qualifier key first before the next key, so that you get the
alternative function rather than the usual one.
e.g. Try pressing SHIFT & A together, versus hold SHIFT down and press
A, and see if you always get a capital A. You don't, always. It may
depend on luck, and how your keyboard is scanned. And, depending on
what you're trying to do, you may *need* to do exactly what you want,
first go.
I've just done this on my laptop, repeatedly, and this is the result:
AAAAaAAAAAaaAaAAAAAAAaaAAA
Just the same way as the A key can produce "a" or "A," depending on
you
using it with the shift key. The PrintScreen/SystemRequest key is a
dual purpose key, and which function you get depends on the qualifier
key used with it.
So... if you don't quite get the behaviour you expect, press and hold
down ALT, first.
--
[tim@localhost ~]$ uname -r
2.6.27.25-78.2.56.fc9.i686
Don't send private replies to my address, the mailbox is ignored. I
read messages from the public lists.
12:55 a.m.
On 21.08.2012, Aaron Konstam wrote:
> /usr/share/doc/kernel-doc-(version)/Documentation/sysrq.txt
I appreciate all these tips but none make the sysrq suctions work. I'll
just give up.
1. Look into your kernel .config if m-sysrq is in your kernel:
CONFIG_MAGIC_SYSRQ=y
Standard Fedora kernels have it compiled in, but it is disabled by default.
2. Set "kernel.sysrq = 1" in /etc/sysctl.conf and do a "sysctl -p".
3. Now press the right ALT key together with PrtScrn, keep
holding this combination and press e.g. "s". Now you should see this
in /var/log/messages:
Aug 21 07:53:07 wildsau kernel: [ 1541.017462] SysRq : Emergency Sync
Aug 21 07:53:07 wildsau kernel: [ 1541.017702] Emergency Sync complete
4:27 p.m.
On Mon, 2012-08-20 at 13:20 -0700, Rick Stevens wrote:
On 08/20/2012 01:05 PM, Joe Zeff uttered this comment:
> On 08/20/2012 12:55 PM, Aaron Konstam wrote:
>> It is hard to know where to start with the problems with the use of the
>> SysReg key.. Since acording to the Wikipedia notes in order to get these
>> Magic SysReg features to work you have tp add the Ctrl button. So to
>> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
>> workstation Keyboard this is nearly impossible to do because of the
>> position of the SysReg key in the upper right corner of the keyboard.
>> On my laptop where I can hit the keys the function fails to work.
>> Without the Ctrl all you get is screen shots which I do get.
>>
>> With the alternate approach of:
>> echo key > /proc/sysreq-trigger the reboot works but I can't detect
>> anything else working.
>>
>> So how does one use these magic keys ?
>>
>
> I can't speak for anybody else, but when I've experimented with it, I
> used both hands.
It's supposed to be a simultaneous press of ALT, SYSRQ (or PRINTSCREEN)
and the command key (B in your case). Note it only works if
/proc/sys/kernel/sysrq contains a non-zero value. To enable ALL
functionality, first set /proc/sys/kernel/sysrq to the value "1":
echo "1" >/proc/sys/kernel/sysrq
Then hit your key combo. Some keyboards may have issues with so many
simultaneous keypresses. In those cases hold down ALT, then press and
release SYSRQ, then press and release your command key and finally
release ALT.
It's been a while since I futzed with it. If you have the kernel-doc
RPM installed, it's explained in
/usr/share/doc/kernel-doc-(version)/Documentation/sysrq.txt
I appreciate all these
tips but none make the sysrq suctions work. I'll
just give up.
-
----------------------------------------------------------------------
--
=======================================================================
"Tell the truth and run." -- Yugoslav proverb
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
3:19 p.m.
On Tue, 2012-08-21 at 00:00 +0400, Hiisi wrote:
On 20 August 2012 23:55, Aaron Konstam <akonstam(a)sbcglobal.net>
wrote:
> It is hard to know where to start with the problems with the use of the
<--SNIP-->
>
> So how does one use these magic keys ?
> --
Could you please post the link to the wikipedia?
--
Hiisi.
Registered Linux User #487982. Be counted at: http://counter.li.org/
--
Spandex is a privilege, not a right.
link Is:
http://en.wikipedia.org/wiki/Magic_SysRq_key
--
=======================================================================
Ha. For once you're both wrong but not where you are thinking. - Larry
McVoy to Linus Torvalds on linux-kernel
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
3:34 p.m.
On 08/20/2012 01:20 PM, Rick Stevens wrote:
It's supposed to be a simultaneous press of ALT, SYSRQ (or
PRINTSCREEN)
and the command key (B in your case).
I've had good results from pressing the keys sequentially, but not
releasing any of them until they're all pressed. YMMV, of course, but
it's worth a try.
3:33 p.m.
On Mon, 2012-08-20 at 13:26 -0700, Rick Stevens wrote:
On 08/20/2012 01:24 PM, Aaron Konstam uttered this comment:
> On Mon, 2012-08-20 at 13:05 -0700, Joe Zeff wrote:
>> On 08/20/2012 12:55 PM, Aaron Konstam wrote:
>>> It is hard to know where to start with the problems with the use of the
>>> SysReg key.. Since acording to the Wikipedia notes in order to get these
>>> Magic SysReg features to work you have tp add the Ctrl button. So to
>>> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
>>> workstation Keyboard this is nearly impossible to do because of the
>>> position of the SysReg key in the upper right corner of the keyboard.
>>> On my laptop where I can hit the keys the function fails to work.
>>> Without the Ctrl all you get is screen shots which I do get.
>>>
>>> With the alternate approach of:
>>> echo key > /proc/sysreq-trigger the reboot works but I can't detect
>>> anything else working.
>>>
>>> So how does one use these magic keys ?
>>>
>>
>> I can't speak for anybody else, but when I've experimented with it, I
>> used both hands.
>
> Ok, it can be reached when you use both hands but it still does not work
> for me. Does it matter which Ctrl key you use?
It shouldn't, but it's not "CTRL", it's "ALT".
ALT-SYSRQ-commandkey
> Just to be clear, in /etc/sysctl.conf I changed: kernel.sysrq to 1 from
> 0.
Did you "sysctl -p" or reboot after doing that?
-
yes I did.
--
=======================================================================
To fear love is to fear life, and those who fear life are already three
parts dead. -- Bertrand Russell
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
3:29 p.m.
On 20 August 2012 21:24, Aaron Konstam <akonstam(a)sbcglobal.net> wrote:
> I can't speak for anybody else, but when I've
experimented with it, I
> used both hands.
Ok, it can be reached when you use both hands but it still does not work
for me. Does it matter which Ctrl key you use?
Offtopic: Almost 20 years ago one of
my friends used to teach
computing to 10 year olds (DOS days). When he was trying to teach how
to do CTRL-ALT-DEL, he fell off laughing when one of his students held
CTRL using one finger on one hand, ALT using an other finger on the
other hand and then hit the ALT using his nose...
Try that method in doubt. :)
(Hint, if it's a laptop, you might have to use the so-called function key)
--
Hakan (m1fcj) - http://www.hititgunesi.org
"What part of 'ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl
fhtagn'
don't you understand?"
3:26 p.m.
On 08/20/2012 01:24 PM, Aaron Konstam uttered this comment:
On Mon, 2012-08-20 at 13:05 -0700, Joe Zeff wrote:
> On 08/20/2012 12:55 PM, Aaron Konstam wrote:
>> It is hard to know where to start with the problems with the use of the
>> SysReg key.. Since acording to the Wikipedia notes in order to get these
>> Magic SysReg features to work you have tp add the Ctrl button. So to
>> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
>> workstation Keyboard this is nearly impossible to do because of the
>> position of the SysReg key in the upper right corner of the keyboard.
>> On my laptop where I can hit the keys the function fails to work.
>> Without the Ctrl all you get is screen shots which I do get.
>>
>> With the alternate approach of:
>> echo key > /proc/sysreq-trigger the reboot works but I can't detect
>> anything else working.
>>
>> So how does one use these magic keys ?
>>
>
> I can't speak for anybody else, but when I've experimented with it, I
> used both hands.
Ok, it can be reached when you use both hands but it still does not work
for me. Does it matter which Ctrl key you use?
It shouldn't, but it's not "CTRL", it's "ALT".
ALT-SYSRQ-commandkey
Just to be clear, in /etc/sysctl.conf I changed: kernel.sysrq to 1
from
0.
Did you "sysctl -p" or reboot after doing that?
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, AllDigital ricks(a)alldigital.com -
- AIM/Skype: therps2 ICQ: 22643734 Yahoo: origrps2 -
- -
- Physics is like sex ... it may give some practical results, but -
- that's not why we do it. -- Richard Feynman
----------------------------------------------------------------------
3:25 p.m.
On 08/20/2012 01:12 PM, Konstantin Svist wrote:
In non-graphical mode it's just Alt+SysRq (not Ctrl, and not
Alt+Ctrl),
but the GUI can choose to ignore the combination - there used to be some
X keyboard setting you could set globally, but it doesn't work anymore.
I think there's some workaround for gnome, but I never did figure out
how to make it work right in XFCE.
I've found on my desktop that if I'm at an alternate terminal, without
the GUI being active, I can usually get it to work if I use the right
Alt key, but not the left; if start with the Control key, however, it
works just fine with either Alt key. So far, I've not tried it on my
laptop.
3:24 p.m.
On Mon, 2012-08-20 at 13:05 -0700, Joe Zeff wrote:
On 08/20/2012 12:55 PM, Aaron Konstam wrote:
> It is hard to know where to start with the problems with the use of the
> SysReg key.. Since acording to the Wikipedia notes in order to get these
> Magic SysReg features to work you have tp add the Ctrl button. So to
> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
> workstation Keyboard this is nearly impossible to do because of the
> position of the SysReg key in the upper right corner of the keyboard.
> On my laptop where I can hit the keys the function fails to work.
> Without the Ctrl all you get is screen shots which I do get.
>
> With the alternate approach of:
> echo key > /proc/sysreq-trigger the reboot works but I can't detect
> anything else working.
>
> So how does one use these magic keys ?
>
I can't speak for anybody else, but when I've experimented with it, I
used both hands.
Ok, it can be reached when you use both hands but it still does not work
for me. Does it matter which Ctrl key you use?
Just to be clear, in /etc/sysctl.conf I changed: kernel.sysrq to 1 from
0.
--
=======================================================================
"He flung himself on his horse and rode madly off in all directions."
=======================================================================
Aaron Konstam telephone: (210) 656-0355 e-mail: akonstam(a)sbcglobal.net
3:20 p.m.
On 08/20/2012 01:05 PM, Joe Zeff uttered this comment:
On 08/20/2012 12:55 PM, Aaron Konstam wrote:
> It is hard to know where to start with the problems with the use of the
> SysReg key.. Since acording to the Wikipedia notes in order to get these
> Magic SysReg features to work you have tp add the Ctrl button. So to
> reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
> workstation Keyboard this is nearly impossible to do because of the
> position of the SysReg key in the upper right corner of the keyboard.
> On my laptop where I can hit the keys the function fails to work.
> Without the Ctrl all you get is screen shots which I do get.
>
> With the alternate approach of:
> echo key > /proc/sysreq-trigger the reboot works but I can't detect
> anything else working.
>
> So how does one use these magic keys ?
>
I can't speak for anybody else, but when I've experimented with it, I
used both hands.
It's supposed to be a simultaneous press of ALT, SYSRQ (or PRINTSCREEN)
and the command key (B in your case). Note it only works if
/proc/sys/kernel/sysrq contains a non-zero value. To enable ALL
functionality, first set /proc/sys/kernel/sysrq to the value "1":
echo "1" >/proc/sys/kernel/sysrq
Then hit your key combo. Some keyboards may have issues with so many
simultaneous keypresses. In those cases hold down ALT, then press and
release SYSRQ, then press and release your command key and finally
release ALT.
It's been a while since I futzed with it. If you have the kernel-doc
RPM installed, it's explained in
/usr/share/doc/kernel-doc-(version)/Documentation/sysrq.txt
Your mileage may vary. Batteries not included. Void where prohibited.
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, AllDigital ricks(a)alldigital.com -
- AIM/Skype: therps2 ICQ: 22643734 Yahoo: origrps2 -
- -
- When in doubt, mumble. -
----------------------------------------------------------------------
3:12 p.m.
On 08/20/2012 12:55 PM, Aaron Konstam wrote:
It is hard to know where to start with the problems with the use of
the
SysReg key.. Since acording to the Wikipedia notes in order to get these
Magic SysReg features to work you have tp add the Ctrl button. So to
reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
workstation Keyboard this is nearly impossible to do because of the
position of the SysReg key in the upper right corner of the keyboard.
On my laptop where I can hit the keys the function fails to work.
Without the Ctrl all you get is screen shots which I do get.
With the alternate approach of:
echo key > /proc/sysreq-trigger the reboot works but I can't detect
anything else working.
So how does one use these magic keys ?
You have to enable the sysrq key in /etc/sysctl.conf:
kernel.sysrq = 1
In non-graphical mode it's just Alt+SysRq (not Ctrl, and not Alt+Ctrl),
but the GUI can choose to ignore the combination - there used to be some
X keyboard setting you could set globally, but it doesn't work anymore.
I think there's some workaround for gnome, but I never did figure out
how to make it work right in XFCE.
Lastly, on the laptop the SysRq key might only be usable with Fn
modifier (Ctrl+Alt+Fn+SysRq+...), though Alt+PrintScreen has worked for
me on all laptops I've tried (in text mode)
3:05 p.m.
On 08/20/2012 12:55 PM, Aaron Konstam wrote:
It is hard to know where to start with the problems with the use of
the
SysReg key.. Since acording to the Wikipedia notes in order to get these
Magic SysReg features to work you have tp add the Ctrl button. So to
reboot you would have to use the Ctrl+Alt+SysReg+ b button. On my
workstation Keyboard this is nearly impossible to do because of the
position of the SysReg key in the upper right corner of the keyboard.
On my laptop where I can hit the keys the function fails to work.
Without the Ctrl all you get is screen shots which I do get.
With the alternate approach of:
echo key > /proc/sysreq-trigger the reboot works but I can't detect
anything else working.
So how does one use these magic keys ?
I can't speak for anybody else, but when I've experimented with it, I
used both hands.
4:59 a.m.
On Wednesday, 22. August 2012. 15.05.05 Joe Zeff wrote:
On 08/22/2012 02:17 PM, jdow wrote:
> Even with the reminders I've seen people keep forgetting that most
> modern keyboards are two key roll-over keyboards. The keys are matrix
> scanned in a fashion that any two keys pressed at the same time can
> be detected but more than two keys pressed at the same time is very
> iffy. You guys may be fighting an inherent keyboard problem rather
> than an OS deficiency.
That may be why some of the instructions for this call for pressing
Alt-SysRq (pause) Command, and why I've had best luck with pressing the
keys one at a time and holding them down until all are pressed.
Umm, no, you are *supposed* to keep them pressed. The problem with two-key
rollover keyboard is that it will not detect a third keypress until one of the
previous two was released. And that is the dealbreaker in using the MagicSysRq
functionality.
It is a good thing to understand how this sysrq thing actually works, and for
that one needs to know how a keyboard actually works (on a fairly low level).
When a key is pressed, the press-scancode of that key is sent to the keyboard
buffer. When the key is released, the release-scancode of that key is sent.
Note that press-scancode and release-scancode are different things. If you
press the key and keep it pressed, eventually the keyboard-repeat
functionality kicks in, and the press-scancode starts being sent over and
over. All keys on the keyboard work that way (and I mean *all*, bar maybe the
"Fn" key on some laptops).
The press- and release-scancodes in the keyboard buffer are being interpreted
by the kernel, translated via a table into keypress/keyrelease combinations,
and then sent down to everything else, including X and stuff. Now, the kernel
can react (independently of anything else) to some specific scancode
combinations, before any other app even gets the idea that something was
pressed on the keyboard. That's where the MagicSysRq functionality kicks in.
The trick is that this specific scancode combo that needs to be sent to the
kernel needs to be convoluted enough so that it cannot occur accidentally.
Therefore, it is a sequence of *press-scancodes*, corresponding to the
combinations such as ctrl+alt+sysrq+b, and no release-scancodes in between.
This means the following:
(1) you need to press the buttons in *that* particular *order* , one by one,
(2) you must not release any of them until all have been pressed,
(3) you must be fast enough so that keyboard-repeat doesn't kick in (most
commonly this means faster than 1/4 of a second),
(4) your keyboard hardware must be able to detect four keys pressed in a row
(without releasing any of them).
Various cheap keyboards cannot satisfy (4), various people are not fast enough
for (3), and various instruction manuals do not emphasize (1) and (2) well-
enough.
In addition to this, note that left-ctrl/shift/alt have *different* scancodes
than right-ctrl/shift/alt. I am not sure if the kernel is designed to watch
out for all combinations (ll, lr, rl, rr), nor the interchange in order of
ctrl and alt. So it is best to try out all combinations, to be certain.
Finally, the "b" key is where "b" is meant to be on a QWERTY keyboard.
If you
have a keyboard with a different layout (DVORAK for example), this key will
likely be labbeled as something else, so watch out for that.
There is a nice table with all keys and their functions in sysrq mode here:
http://en.wikipedia.org/wiki/Magic_SysRq_key
As a side note, I've also seen keyboards with a spacebar that has two
"key"-
mechanisms beneath (on the left and right side), so that two different press-
scancodes are being sent when you press the spacebar, detecting whether you
have pressed it from the left or right side. This was exploited in some
pinball games, with options "kick the pinball machine with the left/right
foot" were simulated by pressing the spacebar from the left or from the
right... ;-)
If you want to experiment with scancodes and keycodes, read "man showkey" and
try it out in the text terminal (outside X).
HTH, :-)
Marko
3 p.m.
On 20 August 2012 23:55, Aaron Konstam <akonstam(a)sbcglobal.net> wrote:
It is hard to know where to start with the problems with the use of
the
<--SNIP-->
So how does one use these magic keys ?
--
Could you please post the link to the wikipedia?
--
Hiisi.
Registered Linux User #487982. Be counted at: http://counter.li.org/
--
Spandex is a privilege, not a right.
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34 comments
12 participants
participants (12)
-
Aaron Konstam -
Fred Smith -
Hakan Koseoglu -
Heinz Diehl -
Hiisi -
jdow -
Joe Zeff -
Konstantin Svist -
Marko Vojinovic -
Reindl Harald -
Rick Stevens -
Tim