There seems to be some confusion about EFI booting and Ubuntu ISOs.
Disclaimer: I don't know much about Macs, because I never happened to own or support one of these machines. But I want to help anyway.
Linux and Windows UEFI booting and Ubuntu Mac ISOs
Using Linux on Windows machines, my understanding is that to boot from external media via EFI you just copy the files from the ISO to a supported filesystem on the USB drive, which is usually FAT. ISOs that support UEFI booting contain a file called /efi/boot/boot{arch}.efi
, where {arch}
can be x64
for AMD64, ia32
for i386, arm
or a64
for ARM and so forth. On (older) Macs this may just be /efi/boot/boot.efi
.
Okay, that's that. The strange thing is that the Mac ISOs don't contain such files and instead boot and install in legacy BIOS mode, which was fine in 2006 – when Apple introduced Boot Camp – but isn't since 2012 when the rest of the industry moved to UEFI.
The answers from Chan-Ho Suh and Colin Watson on similar questions don't seem to reflect the current state accurately.
Fixing the problem with UEFI loaders for older Macs
I found a blog entry from AstroFloyd dealing with a very similar problem while being aware of the above.
His solution is to put an EFI loader that allows for loopback loading a UEFI-compatible ISO. Ideally you would just have to put two files on the FAT-formatted USB drive and that's it.
For clarity, all that is now on your USB drive is (relative to the root directory of that drive):
- /efi/boot/boot.iso
- /efi/boot/boot.efi
His instructions are written using Linux tools and dealing with advanced details like setting the partition type, but I guess Windows and off-the-shelf USB drives already provide this configuration by default.
To be clear: Do not use the amd64+mac ISO, use the latest standard one.
Related:
More background information
Rod Smith – who is also around here – has published a very detailed article about EFI-Booting Ubuntu on a Mac on his site. He explains why installing Linux in BIOS mode on a Mac by using a hybrid MBR is at least to say a bad idea and covers a few scenarios of installing Ubuntu on a drive with an existing Mac OS X installation.
He is using his tool Refind, but as far as I know systemd-boot is also capable of booting OS X and working with Macs. It's probably a bit more difficult to configure.