OSX Bootloader
From wikinotes
Mounting the EFI Dir
sudo mkdir /Volumes/esp sudo mount -t msdos /dev/disk0s1 /Volumes/esp
Blessing a boot loader
Disable System Integrity Protection. Restart the computer, then while booting, hold down Command-R to boot into recovery mode. Once booted, navigate to the “Utilities > Terminal” in the top menu bar. Enter csrutil disable in the terminal window and hit the return key.
# first mount your efi partition sudo mkdir /Volumes/esp sudo mount -t msdos /dev/disk0s1 /Volumes/esp # then bless the new boot loader sudo bless --mount /Volumes/esp --setBoot --file /Volumes/esp/EFI/BOOT/bootx64.efi