I have an iMac 7.2, with OS X 10.5.8. I am thinking of installing Ubuntu, but was told by an Apple-certified repairman that Ubuntu would damage my hardware. Is this true?
No that repairman is making you stick to using macs if you have to ask someone ask a computer rapairman that work on pcs and macs
Installing Ubuntu on a Mac should not damage the hardware.
generally you won't find any trouble on installing Ubuntu on iMac. the repairman told you those kind of thing so Apple can monopolize your life (and money of course). I always hate how Apple play.
Short answer : no.
Tid bit longer answer : There really is no reason for it to damage your hardware.
It may not work as well with your hardware (because your iMac software was designed in parallel with your hardware. They were made to work together)... at first, because of compatibility issues. But there's nothing that can't be solved.
The best way to do it is to run virtual os like im doing. Wm seems to do it and selects all the drivers automaticly
Without having it tested I agree with the others that there should be no problem installing Ubuntu on a Mac. As far as I know it works out of the box without any modifications necessary.
The only warning I want to give you is not to do or try to change anything to the EFI firmware using some Linux tool - just stay away from any EFI/BIOS tool.
The Apple supplied EFI has an overheat protection that will "fire up" the fans in case it gets hot. If this protection get's broken and Ubuntu does not properly control the fans you could end up damaging your hardware.
Sorry, I just wanted to add that you can of course use BIOS emulation and EFI boot managers like rEFIt
EFI-Booting Ubuntu on a Mac
well you can loose warranty, also you can face some damage because incompatibity or wrong installation; Some are lucky and some are not, plan ahead what you want to do.
Yes, you can. The repairman was wrong. I'm running a late 2011 iMac with i7, 4GB memory and Ubuntu 12.04- it runs like a charm without any hardware programs. Ubuntu is actually more reliable than 10.5
My advice- go for it.