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I have some VM on qemu, which occasionally freezes.
Thus I need some way to send sysrq to my VM. I use both TigerVNC and picocom, but the appropriate hotkeys (e.g. Alt + PrtScr + B) don't work. Obviously, in this case Alt + PrtScr + B sends sysrq to my host Linux, not VM.

So is there a way to send sysrq to VM through the picocom terminal or TigerVNC?

Seem that it's related to somehow sending "break" in case of picocom.

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  • As a quick pointer, I believe that sending this keystroke may likely be possible using the Qemu monitor, using -telnet so the Qemu software acts as a telnet server (which can be set to listen to only localhost).
    – TOOGAM
    May 3, 2020 at 19:22
  • @TOOGAM it would be nice to see a brief example..
    – red0ct
    May 3, 2020 at 19:31

1 Answer 1

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Here's the linux kernel documentation on SysRq.

per the document On the serial console it says

You send a BREAK, then within 5 seconds a command key.

In the picocom man page we see

C-backslash

         Generate a break sequence on the serial line.

so for sending SIGTERM to all processes it'd be

ctrl+a+ctrl+\+e

Note when picocom shows you ** break sent ** that's a picocom output and not a response from linux.

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