grub-macbless

grub-macbless [OPTION]... [DIRECTORY]

--file=FILE
    use FILE as EFI binary (default: EFI/GRUB/grubx64.efi)

--bootdir=DIR
    bless DIR/EFI/BOOT/BOOTX64.EFI (default: no)

--label=LABEL
    set volume name to LABEL (default: GRUB)

--shortform
    use folder alias instead of full path

--devicepath
    print device path

--folder=DIR
    bless DIR (default: System\Library\CoreServices)

-h, --help
    display this message

-V, --version
    print version information

grub-macbless is a GRUB2 utility for blessing the GRUB EFI bootloader on macOS volumes, enabling the Apple firmware to recognize and boot it. On Macintosh hardware, EFI volumes require a 'blessed' file—typically in System/Library/CoreServices—to be selected as bootable. This command automates the process using macOS's native bless tool, setting boot flags, labels, and paths for HFS+ or APFS filesystems.

It supports installing GRUB to standard EFI/GRUB/grubx64.efi locations or custom files, and can bless EFI/BOOT/BOOTX64.EFI for removable media. Common after grub-install to EFI partitions on external drives or internal macOS volumes for dual-booting Linux.

Run as root (sudo) on the volume's mountpoint. Ensures GRUB appears in Startup Manager (Cmd+Opt+R at boot). Supports x86_64 EFI only.

Requires macOS/Darwin, root privileges, HFS+/APFS volumes. x86_64 EFI only; ARM Macs unsupported. May need volume unmount/remount.

sudo grub-macbless /Volumes/GRUB
sudo grub-macbless --file=grub.efi --label='Linux Boot' /Volumes/MyVolume

GRUB EFI binary present; target volume mounted read-write.

Added in GRUB 2.02 (2012) for refind/rEFIt users; enhanced in later GRUB2 releases for APFS and better EFI handling.

bless(8), grub-install(8), efibootmgr(8)