I want to install Ubuntu on my Intel mac and I don't want any data lost. I also want to completely uninstall Ubuntu if necessary. I'm wondering if this is possible. I have a backup made (with Time Machine) just in-case.
"It won't erase anything".
Partitioning your disk with OS X tools won't erase anything. Open up Disk Utility and click on the 'top-level' of the hard disk in the left-hand side panel. In my case it says:
320.07 GB WDC WD3200BEKT-00F3T0 Media
Then over to the right in the main panel you'll notice five tabs up the top:
Click on 'Partition'. Under 'Volume Scheme' there's a column partially coloured in blue, indicating how much data resides on your HDD. Underneath that you'll see a '+' and a '-' button. Press the '+'. You'll notice you now have two partitions. (Nothing's been written or changed yet. You can still change your mind.) Between the two partitions there's a little handle which you can drag up and down. Move that so you've got enough room for an Ubuntu install. I'd say 20 GB is sufficient but it's very subjective. It's certainly enough to get started, and if you feel you need more down the track you just repeat this procedure.
Click on the new proposed white partition. There's a drop-down box to the right. Choose format as 'Free Space'. Have one last look to make sure you're satisfied and click 'Apply'.
Disk Utility will do its thing and very soon you'll have a brand new empty bit of HDD to install Ubuntu on.
Incidentally, the Live CD is much slower than a native install but it gives you some idea of what to expect.
I note your picture. Did your Disk Utility screen look like this immediately prior to your picture being taken?
Use BootCamp Assistant to create new partition, then remove Windows partition leaving free space for Ubuntu. It's described in detail here:
It should be. Depending on what kind of mac you have you'll need different versions (if it's an intel mac you can use any of the ubuntu live cds, I think you'll be able to run x64, but I don't remember if all macs have 64-bit processors. If you're on an PPC mac you'll need to find a powerpc build).
I've had Ubuntu installed on an iMac G5 just fine. Granted we weren't trying to save OSX when we did it, but it works fine.
As for a newer mac, I've gotten an 11.04 x32 Beta 1 running on a newer Mac Pro tower. It didn't have unity, but I think that's a problem with the liveCD, I also attribute the slowness of the system to the LiveCD (which has been a problem on non-apple machines too). I would assume it would work fine.
To uninstall it, use an OSX install cd, delete the non-osx partition and resize the osx partition to be the full drive.