Ubuntu – Will Ubuntu run fine in EFI mode on a Macbook that needs to run Windows 10 in legacy (BIOS) mode


I'm wondering about potential issues with installing Ubuntu in EFI mode on a mid-2012 Macbook Air. From what I could gather from this page earlier Macbooks aren't UEFI compliant:

  • 2012 and older models only support legacy BIOS Mode. There is varying degree of 'EFI'ness in these, but they are not UEFI-compliant.
  • Late 2013-2014 models support both EFI and BIOS, and default is BIOS. These are the first models which are UEFI.
  • 2015 and later models only support EFI and UEFI-compliant.

I don't know if that is accurate nor if it has any impact on an Ubuntu install.

Quick facts about this machine:

  • macOS Mojave (i.e. APFS)
  • GPT partitioned drive (a Samsung SSD)
  • Windows 10 64-bit installed through BootCamp Assistant
  • Windows 10 runs in Bios/legacy mode judging from that…
    • Windows sees the drive as MBR
    • Windows only installs to MBR drives in legacy mode
    • The drive has a hybrid MBR

I'm trying to determine whether it's worth creating a GPT-only partition for Ubuntu and whether to install it in EFI or legacy mode (assuming I have a choice between the two), because regenerating a hybrid MBR would be moderately risky.

Best Answer

  • Some early Intel Macs with 64 bit processors had only a 32 bit EFI in the firmware. There used to be versions of Ubuntu installers which would create a BIOS booting GRUB. However, GRUB still recognized and used the GPT partitioning table. In these cases, the drives were hybrid partition only because the Mac firmware would not BIOS boot unless there was hybrid partitioning. Once Ubuntu was booted by GRUB, Ubuntu would ignore then hybrid partitioning and only use the GPT.

    At least since 2007, all Intel Macs have a 64 bit EFI. For these Macs, Ubuntu should be installed to 64 bit EFI boot even if the EFI is not UEFI compliant. Any hybrid partitioning is ignored by GRUB and Ubuntu.

    In conclusion, there is no good reason to hybrid partition for the sole purpose of installing Ubuntu on a 2012 Mac. If you already have Window installed to BIOS boot, then Ubuntu can be installed to EFI boot and will ignore the hybrid partitioning.