alt-sysrq to linux guest

Discussion in 'Linux Virtual Machine' started by SPelly, Nov 2, 2011.

  1. SPelly

    SPelly Member

    Messages:
    27
    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?
     
  2. SPelly

    SPelly Member

    Messages:
    27
    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.)
     

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