Stupid KVM tricks

I needed to install Red Hat Enterprise Linux 4 on a machine at work today; normally, that’s a very simple process, marked only by tedium.

Not this time. When I first tried running the install CD-ROM, the screen blanked and I couldn’t wake it up; a friend suggested using the text-mode installer to get around the problem. And, indeed, that did get me through the install — but then when the system booted, the screen went blank and I couldn’t wake the system up.

So I tried reinstalling, with no change; I even tried to use Ubuntu, but it died in the same way.

I thought it must be a hardware problem, but before punting, I asked for help. My colleague came down and walked me through the install, and we had the same results. But then she had a brainstorm — we booted into single-user mode successfully and compared the xorg.conf file on my machine with one that worked. And, sure enough, there were significant differences.

Apparently the KVM on this bank of systems lied to anaconda, so that the installer wrote a configuration file claiming that the display could work at frequencies which were far in excess of what it could really handle. I edited the file to specify horizontal rates around 35 and vertical rates of around 60, and all was well.

Then I changed /etc/inittab to only come up in runlevel 3, which would have worked, too; since I never plan to use the physical console again (it’s in a very loud and very cold machine room), there’s no sense in starting X there.

Moral of the story: don’t panic. And wear earplugs.