How to install Linux 64-bit Distro on older 32-bit EFI booting Macs (tested with MacPro model 1,1)

The MacPro 1,1 along with other legacy models from around 2006 (the Core2Duo era) are capable of running 64-bit operating systems and applications, but were produced with a 32-bit EFI ROM. This means the installation process requires conversion of an official ISO into 32-bit EFI compliant media.

Instructions

Boot Media Creation

• Download desired Linux ISO (Note: I've only had success with Ubuntu 2̶0̶.̶0̶4̶.̶1̶ ̶L̶T̶S̶, 16.04.7 AMD 64Bit version)
• Verify the ISO with SHA256 checksum, see instructions here
• Download the enclosed isomacprog.c script
• Doublecheck the script, never run anything without doublechecking! ;)
• Compile the script: cc -g -Wall isomacprog.c -o isomacprog
• Make a copy of the ISO as a backup: cp <original-iso-name>.iso macversion.iso
• Run the compiled script against the copy of the ISO ./isomacprog macversion.iso
• Check terminal/console for errors, although only basic error handling is included.
• burn the macversion.iso to CD/DVD Disk Utility is fine: right click the macversion.iso file and click burn to disk

Installation

• Boot your mac up, and insert the DVD
• Restart the mac and hold the 'option' key
• The boot media will be called 'Windows' and have a disk icon, click this to start the install
• When the boot loader asks 'what would you like to do?', identify the disk you want to install ubuntu on, and select 'erase entire disk'
• IMPORTANT In Device for boot loader installation, change this to match the same disk identifier as the Ubuntu disk (I.e. /dev/sdb)
• Click continue, and follow the remaining prompts.
• When wanting to boot up in Ubuntu, simply hold the Option key and select the Hard Drive labelled 'Windows'

Acknowledgements

^{Matt Gadient's Linux DVD images and how-to for 32-bit EFI Macs late 2006 models link
Thomas Schmitt: 64-bit to 32-bit ISO conversion script link}