I recently had a need to install Linux on a 2014 Mac Mini. Naturally I chose Centos! 😄 I had some trouble finding a straightforward HOWTO to follow, so for the benefit of others wanting to do the same thing, here are the steps I took:

• download the latest Centos 7 minimal ISO, and transfer that to a USB stick using dd e.g.

sudo dd if=CentOS-7-x86_64-Minimal-1708.iso of=/dev/sdb bs=8M

• insert the USB stick into the Mac Mini
• (re)boot the Mac Mini and hold the C key (or Alt/Option) down immediately after power on - this will take you to a boot disk selection screen
• select the USB stick (labelled ’efi’) and proceed to boot from it
• from here is a standard Centos install routine, with the exception of disk partitions:
  • peform a manual disk partition setup.
  • You should see 3 existing logical partitions: the EFI partion, the partition holding the existing MacOS install, and a recovery partition of around 600MB.
  • wipe the MacOS partition and add your Centos mountpoints there as required. (keep the MacOS recovery partition in case you want to revert back in future)
  • ensure that the existing EFI partition gets mounted to /boot/efi
• proceed with Centos install

Something odd I noticed was that the onboard NIC did not show any link light when plugged in, however the network was connected (after I ran dhclient to get an IP).