Upgrading boot from GPT(BIOS) to GPT(UEFI)

[Eric van Gyzen]

On 12/16/2016 11:08, Fernando Herrero Carrón wrote:
> Hi everyone,
> 
> A few months ago I got myself a new box and I have been happily running
> FreeBSD on it ever since. I noticed that the boot was not as fast as I had
> expected and I've realized that, while my disk is GPT partitioned, the boot
> process is still BIOS based:
> 
> % gpart show
> =>       34  976773101  ada0  GPT  (466G)
>          34          6        - free -  (3.0K)
>          40       1024     1  freebsd-boot  (512K)
>        1064        984        - free -  (492K)
>        2048   67108864     2  freebsd-swap  (32G)
>    67110912  909662208     3  freebsd-zfs  (434G)
>   976773120         15        - free -  (7.5K)
> 
> I am reading uefi(8) and it looks like FreeBSD 11 should be able to boot
> using UEFI straight into ZFS, so I am thinking of converting that
> freebsd-boot partition to an EFI partition, creating a FAT filesystem and
> copying /boot/boot.efi there.
> 
> How good of an idea is that? Would it really be that simple or am I missing
> something? My only reason for wanting to boot with UEFI is faster boot,
> everything is working fine otherwise.

I would recommend creating another partition for EFI instead of replacing your
freebsd-boot partition, in order to have a working fallback in case EFI boot
doesn't work.  You would need to steal some space from your swap partition.

Otherwise, it's a good idea, and it really is that simple.  I did exactly that
when I updated a machine to 11 and switched to EFI.

$ gpart show ada0
=>       34  500118125  ada0  GPT  (238G)
         34          6        - free -  (3.0K)
         40       1024     1  freebsd-boot  (512K)
       1064       1600     2  efi  (800K)
       2664   10485144     4  freebsd-swap  (5.0G)
   10487808  489629696     3  freebsd-zfs  (233G)
  500117504        655        - free -  (328K)

$ sysctl machdep.bootmethod
machdep.bootmethod: UEFI

Eric