Upgrade to Ubuntu 14.04 failed on my 2012 late iMac

I should not click 'Yes' while it prompted 'A new version found, do you want to upgrade.'

The whole upgrade process seemed ok, only except some compile errors about out of memory with fontconf....

But at the end of upgrade, it reported the upgrade failed, and it could not roll back to the old 13.04.

I reboot the machine into ubuntu anyway, it brought up everything, and seems a new version already installed, only that the desktop resolution abit low.

But i wouldn't bother myself to figure that out, since I don't know what other potential issues there. Don't want to take any risk and put myself into a even worse situation.

So, after googling a little, I decided to give it a fresh installation with 14.04, for sake of it's a LTS version.

And shame that couldn't find image for mac on ubuntu official download site, finally found it from a forum:

http://cdimage.ubuntu.com/releases/trusty/release/ubuntu-14.04-desktop-amd64+mac.iso
(MD5: 0bc7243aacd5f80f8110dcf3165dffd0)

Downloading now, and hope no other issues with the installation upcoming...