[vox-tech] magic sysreq key

[Mike Simons]

On Tue, Mar 18, 2003 at 01:33:38PM -0800, Peter Jay Salzman wrote:
> begin Mike Simons <msimons@moria.simons-clan.com> 
> >   Keep in mind sysrq works form inside X too... 
[...]
> >   X can not trap or block those key sequences...
> 
> that is what it looks like when i type "alt-sysreq-h" from within X.
> 
> i would say that X is definitely catching the key sequence.  or else the
> scancode is changing for some reason...

I wrote:
#   The output goes into the kernel message buffer, which will appear on
# the console, in dmesg, and some /var/log files depending on how you have
# klogd setup...
#   After hitting A-S-h you should see something like:
# 
# dmesg | tail -1
# ===
# SysRq : HELP : loglevel0-8 reBoot tErm kIll saK showMem Off showPc unRaw
# Sync showTasks Unmount
# ===

from the documentation:
% *  What is the magic SysRq key?
% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
% It is a 'magical' key combo you can hit which the kernel will respond to
% regardless of whatever else it is doing, unless it is completely locked up.

Pete,

  Type your Alt-Sysrq combo, then look at dmesg or 
tail -f /var/log/kern.log.  The command sequence is being run.

  The sysrq keys would be rather useless if they didn't work inside X...
since most people live in X.

  The kernel owns the keyboard input devices, and is always the thing 
interpreting the keystrokes to pass to the application running on the
"active" console.

  This option's user interface is rather crude, which is why it's under 
"Kernel Hacking" in the configuration menus... it's not meant to be used
by everyone, Linux isn't supposed to be unstable, and you only need
it if something breaks.  

  So test it out inside X, and let me know if it doesn't work.

    Later,
      Mike