I'd recently used the general approach from the Ubuntu wiki to set up an old Intel iMac with dual-boot Leopard/Intrepid, and everything went like clockwork:
- Boot from the Leopard install DVD
- Early in the OS X install process, use Disk Utility to create a small HFS Plus partition and a big partition I would later snuff for use by Ubuntu, then install Leopard.
- Install rEFIt.
- Use a GParted LiveCD to turn the partition from step 2 into free space.
- Install Ubuntu Intrepid from a LiveCD.
That was odd, since lots of people have reported successfully installing various Ubuntu versions on Mac Pros.
Now, black screens for Ubuntu are not unusual; they generally indicate some kind of driver or X configuration mismatch. I routinely run into them when doing kernel updates on one of my boxen, and the usual search engines offer lots of hits for solutions. But none of the usual techniques worked on this particular Mac Pro.
To cut to the chase, here's the solution. Starting after Step 3 above...
- From the Mac System Profiler, determine the manufacturer and details of your video card. (Mine was an ATI Radeon HD 2600 with 256 MB RAM.)
- Start the installation from the Ubuntu Alternate CD, which uses an old DOS-style text mode for its user interface. (If you use the LiveCD or LiveDVD, it will try to go into graphics mode and you're toast.)
- Zap that big partition you made as part of the installation process. You may also have to manually specify the size of your swap space. You can look up details on how to do this using the usual search engines.
- When you reboot at the end of your Ubuntu install, you'll get the black screen. Press command-control-F1 to switch to a command prompt. (The meta-keys may be different if you picked a non-Macintosh keyboard during install.)
- Use sudo apt-get to update everything, and reboot.
- When the screen goes black, use the key combo again to get a command prompt. Use sudo apt-get to install envyng-gtk. Then do sudo envyng -t.
- Pick the manufacturer of your video card from the envyng list, then reboot.