The recurring scrambled screen in ARD

This has happened to me twice, and I’m not the only one.

While I think there are probably multiple causes, for me, this is the 100% cause and fix.

You have a machine which repeatedly presents in ARD (or your favourite VNC client) with the screen scrambled, in a pretty classic “it thinks this pictures a different size” angled lines look (below is just a simulation):

scrambledsim

You can restart ARD via SSH, and the problem goes away, only to return on your next reboot

Trawling the interweb reveals two schools of thought: you’ve either got something wrong with ARD, or loginwindow. We’re not at a flame war yet, but folks for whom a solution doesn’t work are getting anxious

Me, I think it’s both – sometimes deleting loginwindow.plist fixes it, sometimes it is more deep seated. So My fix is:

  • Do what you have to do to connect to the machine (restart ARD; delete loginwindow.plist and ARDAgent.plist and restart ARD; plug a screen into the thing)
  • Dump the two plists if you haven’t already
  • Change resolution on the monitor and back (if you’re ARD/VNC connected you may have to do the above frigmarole again). This writes new prefs files for anything interested in screen resolution.
  • Restart – not 100% necessary, but gurantees prefs files are written to disk for everything.

Bob’s your uncle.

(As I said, this is the second time I’ve had to fix this. And, naturally, now that I’ve written this, I found our solution to it the first time. Jakub was actually a little more succinct…)

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  1. I can shed a little more light on this.
    The problem is actually fixed in OSX 10.5 for starters.

    It occurs if a 10.4 or earlier machine is sitting at a login prompt, and you log-in via ARD.
    When the OS does it’s “detect displays” function during login, it often causes this problem.

    As long as you are on a gigabit connection to the client, the easiest way to resolve it is to send an UPGRADE CLIENT SOFTWARE command from your ARD console. This will basically trigger an ARD kickstart (after sending the latest client version package).

    You will notice as soon as you upgrade a machine to OSX 10.5, if you are connected via ARD and login, as soon as the desktop of the user is displayed, ARD disconnects for a few seconds.
    Not the cleanest fix, but this is Apple’s way of dealing with the issue.

  2. Absolutely fantastic mind blowing thing

    • bruno domingues
    • December 6th, 2010

    Hi there,

    I have that kind of scrumbled screen on my Safari every day!!! I use all the time “Chicken for VNC”, do you think is related? But then why does scramble my Safari ONLY and not the rest of the things, not even my VNC connection?

    Weird, it’s annoying me!

    Cheers

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