I have a Mac Pro 1,1 and I replaced the original hard drive with a new 3TB hard drive (just got, never initialized). I try to install ubuntu by a bootable USB stick which I crated on my Mac When I fellow the instruction on [https://help.ubuntu.com/community/MacPro] However I find out it does not work. And in this instruction, it mentioned Mac pro 1,1 is EFI incompatibilities, That is also the reason I can not install rEFind. This instruction has a link [http://cdimage.ubuntu.com/releases/11.04/release/] seems can help my situation, but that page is not available. Now the bootable USB stick never show up when I restart my Mac pro with pressing the option button. I appreciate any answer can help me out.
Look for the ISO's with "amd64+mac" in the name. There are both Desktop and Server versions.
Go to this page: http://cdimage.ubuntu.com/releases/14.04/release/ to see the full list of available ISO's for download. Again, look for the "amd64+mac." It's faster to download them as torrents if you can.
My aim is to convert three of these Mac Pros into Ubuntu servers along with an XServe 1,1 as their master for a private cloud at work. All of them have 32GB RAM installed, and these machines are still in great condition. I'd hate to have to discard them just because Apple will no longer update Mac OS X Lion when Yosemite is released.
The Mac Pro 1,1 is special in that it has a 32-bit EFI. Later models have a 64-bit EFI which does not have as many issues installing linux.
The easiest way to run Ubuntu (or any linux, really) on a Mac Pro 1,1 (2006) is installing VirtualBox on your MacOsX, and running linux in a virtual machine.
The alternative is described here: https://wiki.debian.org/DebianOnIntelMacPro
But, again, save yourself a lot of hassle and just run linux in a virtual machine.
What I had to do is install the amd64 version of Ubuntu 12.04, and then go through the upgrade to 14.04, and then 16.04. Pain in the posterior extremus, but it worked, and much more satisfactory than what I had to do before, which was run 32-bit Ubuntu (on a Mac Pro with dual quad-core 64-bit processors.)