Random blank/black X sessions with GDM on a Dell GX280 running CentOS 5

While upgrading a lab of Dell GX280 systems to CentOS 5 today I ran into a bit of a snag. Seemingly at random when the system initially started or returned to the GDM login screen the user would get a black screen. The system still responded on the network, could be switched to VTs and the GDM screen would correctly display after a few gdm-restart commands. I found this bug report but no solution. I did notice that when the screen was blank if the mouse was moved up, till it the cursor (were it visible) would hit the top of the screen, the GDM screen would pop up and function normally.

I fully realize that this is very hackish and should not be used as a long term solution but it works in this case to eliminate user confusion until a real fix is found. All instructions assume file paths and conventions in CentOS but should work with minor modifications anywhere else this problem is encountered.

A bit of searching turned up xdotool, a command for simulating keyboard and mouse input using the X11 XTEST module.

I created an RPM spec file that will download and build and xdotool package, available here: http://pastie.textmate.org/162710

Once xdrtool is installed do the following:

  1. Edit your /etc/X11/xorg.conf, add Load "xtest" to the Module section
  2. Copy /etc/gdm/Init/Default to /etc/gdm/Init/:0
  3. Edit /etc/gdm/Init/:0 to include something similar to this towards the bottom: 
    (sleep 1 ; xdotool mousemove 0 0 ; sleep 1 ; xdotool mousemove 640 450) &

This will cause the pointer to jump to the upper left corner of the screen and then back to the center just after GDM starts. At the moment this appears to reliably work around the problem.

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