alt-sysrq to linux guest

[SPelly]

Hi, I'm using Parallels (build: 7.0.15050) to run a Linux guest on my MacBook Pro. Part of my workflow requires sending an Alt-PrintScreen immediately followed by a command key to the guest. My kernel seems to be configured correctly. I tested that by sending the command key to /proc/sysrq-trigger. When I do, Linux produces the expected result.

When I try from the keyboard using: Devices=>Keyboard=>Alt+PrintScreen followed by command key, I get nothing (not even echoing of the command key).

Has anyone done this from a keyboard?

note: my guest os does not have Parallels tools installed. Does anyone know if they are required for the guest to see the Alt+PrintScreen?

 

[SPelly]

After some closer examination I figured out what's happening.

Linux expects to see:
[alt key down] [PrintScreen key down] [PrintScreen key up] [command key down] [command key up] [alt key up]

The important thing is that the alt key is down until the end of the sequence.

The Devices=>Keyboard=>Alt+PrintScreen menu item releases the alt key before there is an opportunity to type the command key.

Holding the alt key while selecting Devices=>Keyboard=>PrintScreen from the menu doesn't work either. Turns out that the keyboard scan codes are completely different for PrintScreen vs. Alt+PrintScreen.

I wish the Devices=>Keyboard=>PrintScreen menu selection understood that the alt key was down, and sent the Alt+PrintScreen scan codes but waited to send the "Alt key up" scan code until the key was released.

Plugging an external USB keyboard that has a real PrintScreen key works around the problem but isn't very portable. (the keyboard is bigger than my MBP. it is lighter, though.)