[systemd-devel] Bind key combination to isolate emergency mode

[Thomas Meyer]

Am Samstag, den 20.06.2015, 18:01 +0300 schrieb Mantas Mikulėnas:
> On Sat, Jun 20, 2015 at 5:26 PM, Thomas Meyer <thomas at m3y3r.de> 
> wrote:
> > Hi,
> > 
> > Is it possible to bind a key combination in systemd to perform a 
> > switch into emergency mode or another target?
> > 
> > And would this key binding also work in situations where the system 
> > is under heavy cpu load and heavy swapping?
> Sort of. There's a single key combination (Alt+ArrowUp by default) 
> which maps to kbrequest.target, though it only works on the console 
> and not within Xorg & the likes. You can pull in emergency.target via 
> that.
> 
> Also don't forget the magic SysRq keys – Alt+SysRq+F will run the OOM 
> killer in case of heavy swapping, Alt+SysRq+E/I will sigterm/sigkill 
> all programs (systemd will restart gettys afterwards), and 
> Alt+SysRq+N will renice high-priority processes. You need to enable 
> this via sysctl.conf though.

Hi Mantas,

thanks for the hint. I will try this.
I remember that SysRq was once always enabled? It now seems to be
disabled in current Fedora releases. I think enabling F key should be
default. At least it shouldn't be possbile to do something bad with it,
or is it?

> 
> -- 
> Mantas Mikulėnas <grawity at gmail.com>