Aug 3, 2019

FreeBSD 12.0: EFI dual-boot with GNU/Linux

The FreeBSD installation using the live installer was easy and smooth, except the disk partition part where I decided not to create an EFI partition for FreeBSD, because I hated having 2 EFI partitions on the same disk.

The trick here is to to copy EFI boot program BOOTx64.efi (i.e. from the live USB) to the existing EFI partition on my disk, and then use other system’s grub2 to automatically detect the EFI boot program and create a boot entry for our FreeBSD.

So we will use an existing Linux system that you want to dual-boot FreeBSD with to copy the EFI file to the EFI partition, the destination path in the FAT32 partition should be \EFI\FreeBSD\BOOTx64.efi.

As of writing this blog post, I was using Manjaro Linux, which mounts its EFI partition under /boot/efi, so I copied BOOTx64.efi to /boot/efi/EFI/FreeBSD/BOOTx64.efi.

Then I edited the 40_custom file in /etc/grub.d to look something like:

# [ /etc/grub.d/40_custom ]

# FreeBSD was installed without creating its own FAT32 EFI partition
# The EFI boot file in this case is located on disk 0, GPT partition 4
# The FreeBSD root filesystem is UFS

menuentry "FreeBSD" --class freebsd --class bsd --class os {
 insmod bsd
 insmod ufs2
 chainloader (hd0,gpt4)/EFI/FreeBSD/BOOTx64.efi
}

Then, update grub configuration file (on Arch Linux) with:

sudo update-grub;

Manjaro-shipped grub should detect FreeBSD installation as ‘unknown Linux distrobution’. Then reboot, and your grub menu should now present you with an entry for FreeBSD.

Note: this was written back in 2019 and may no longer be relevant.