Thanks to some of the hints, I got a mirror setup (both CRT + LCD) to work properly on an iBook. I'll give a presentation on Wednesday so that's pretty cool.
Here's the way to go: - startup normally * booting with closed lid not required (1) * booting into OSX first not required - startup XFree86 without UseFBDev (2) * using Option "Monitor" "CRT" * using MonitorLayout ... not required - now, the CRT displays the desktop, and the LCD does but improperly (3) - shutting down XFree86, restarting with UseFBDev - voil�, doing something productive (4) Remarks: (1) When booting with lid closed, the LCD is turned on but doesn't display anything. The CRT only displays the OF menu, yaboot menu and the first stage of Linux booting until the frame buffer appears. Then it switches off because the hsync is out of range (180.9 Hz), while vsync is ok (80.6 kHz). (2) When starting with UseFBDev first, the monitor is not recognized. However, (3) ... when starting without UseFBDev, the LCD displays weird lines, and switching to the console does not work (similar experience than what the default woody setup gives) (4) One common task is running OpenOffice. While a relocation error happens when running it as user, this doesn't happen when running as root and then issung su -c "startx" - $user. (Yes, login shell required, otherwise the effect won't take place.) See bug #170044, message from Matthias Urlichs. So having to log in as root is justified anyway, at least for the moment. (5) A bit unrelated, but still interesting: When calling startx & (forking into the background) from within a shell script, I'm told: X: user not authorized to run the X server, aborting. I can start X this way from the bash directly, or from a script without forking, but not a combination of the two. Using 2.4.20-ben1 and dri-trunk packages. Josef -- Free operating systems. Free software. Free games.

