I've (mostly) switched to using a Logitech k400r wireless keyboard for most
of the time with the linux box that feeds AV to our TV, etc. However it
doesn't have a key which is labelled as the sysreq. And when I tried the
'print screen' key to see if that could be used for this purpose it didn't
work.

So, anyone know which key on this model of keyboard will deliver the
sysreq? Or how I can check to find out?

I tried a websearch but couldn't find any specific answer to this.

Jim

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On Sat, 14 Aug 2021 10:16:00 +0100
Jim Lesurf <noise@audiomisc.co.uk> wrote:
> I've (mostly) switched to using a Logitech k400r wireless keyboard for most
> of the time with the linux box that feeds AV to our TV, etc. However it
> doesn't have a key which is labelled as the sysreq. And when I tried the
> 'print screen' key to see if that could be used for this purpose it didn't
> work.
>
> So, anyone know which key on this model of keyboard will deliver the
> sysreq? Or how I can check to find out?

I think keyboards deliver "scancodes" and an application uses a library to
translate from the scancode to a human readable symbol like a letter or a
number , etc. How an application does things also depends on whether it uses
the X Windows API or the Wayland API (or something else ?) and that of course
will also depend on what is running on the Linux box in question. I don't
know if different keyboards will necessarily deliver the same scancode for
the same letter on the keyboard or <X Windows / Wayland / library /
whatever> has some way of doing an appropriate translation depending on the
model of keyboard and possibly other factors.
www.win.tue.nl/~aeb/linux/kbd/scancodes-1.html has some information.

This is all a bit esoteric of course and perhaps will set you towards the
wrong path. A more productive approach may be the following : on the Linux
box in question what application is responsible for reading sysreq (when it
exists) and do the operation you want to achieve ? The documentation of that
application may provide a clue.

> I tried a websearch but couldn't find any specific answer to this.

Have you tried the old and trusted method of pressing random keys and see
if any do what you want ? Obviously this isn't something you should do if
the results can be catastrophic like for example if the same Linux box
controls the self-destruct mechanism of your house.

On Sat, 14 Aug 2021 10:16:00 +0100, Jim Lesurf wrote:

> I've (mostly) switched to using a Logitech k400r wireless keyboard for
> most of the time with the linux box that feeds AV to our TV, etc.
> However it doesn't have a key which is labelled as the sysreq. And when
> I tried the 'print screen' key to see if that could be used for this
> purpose it didn't work.
>
> So, anyone know which key on this model of keyboard will deliver the
> sysreq? Or how I can check to find out?
>
> I tried a websearch but couldn't find any specific answer to this.
>
Does running 'showkey -a' help?

--
--
Martin | martin at
Gregorie | gregorie dot org

In article <VkuwifgCL6SOnqv9H@bongo-ra.co>, Spiros Bousbouras
<spibou@gmail.com> wrote:

> This is all a bit esoteric of course and perhaps will set you towards
> the wrong path. A more productive approach may be the following : on the
> Linux box in question what application is responsible for reading
> sysreq (when it exists) and do the operation you want to achieve ? The
> documentation of that application may provide a clue.

AIUI the purpose of SysKey is that the 'OS' picks this up as a trigger that
what follows is to deal with something like a 'kernel panic'. i.e. it
bypasses (or should) the GUI and apps.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/intro/electron.htm
biog http://jcgl.orpheusweb.co.uk/history/ups_and_downs.html
Audio Misc http://www.audiomisc.co.uk/index.html

On Sun, 15 Aug 2021 14:57:17 +0100
Jim Lesurf <noise@audiomisc.co.uk> wrote:
> In article <VkuwifgCL6SOnqv9H@bongo-ra.co>, Spiros Bousbouras
> <spibou@gmail.com> wrote:
>
> > This is all a bit esoteric of course and perhaps will set you towards
> > the wrong path. A more productive approach may be the following : on the
> > Linux box in question what application is responsible for reading
> > sysreq (when it exists) and do the operation you want to achieve ? The
> > documentation of that application may provide a clue.
>
> AIUI the purpose of SysKey is that the 'OS' picks this up as a trigger that
> what follows is to deal with something like a 'kernel panic'. i.e. it
> bypasses (or should) the GUI and apps.

Is the information at
https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html of any use ?

It might also help if you explain what operation you want to achieve with
sysreq .

--
According to quantum mechanics there exists an alternative universe where there
are movies "Silence of the wolves" and "Dancing with lambs".