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

[Fernando Herrero Carrón]

2016-12-16 23:56 GMT+01:00 Warner Losh <imp at bsdimp.com>:

> On Fri, Dec 16, 2016 at 11:00 AM, Dimitry Andric <dim at freebsd.org> wrote:
> > On 16 Dec 2016, at 18:53, Antony Uspensky <uspensky at x-art.ru> wrote:
> >>
> >> On Fri, 16 Dec 2016, Eric van Gyzen wrote:
> >>> On 12/16/2016 11:39, Slawa Olhovchenkov wrote:
> >>>> On Fri, Dec 16, 2016 at 06:08:34PM +0100, Fernando Herrero Carr?n
> 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 would shrink ada0p1 down to 128K (size of gptzfsboot = 88K now) and
> place efi partition (~800K) on free space between new p1 and p2. No need to
> touch swap partition.
> >
> > Yes, this is almost exactly what I have done on a machine that was
> > originally installed with gptzfsboot on the first partition, which was
> > 512K.  Since all the partitions on this SSD were aligned to 1M, I
> > reduced the size of the first partition to 224K, freeing up a hole of
> > exactly 800K for an EFI partition:
> >
> > =>       40  976773088  ada0  GPT  (466G)
> >          40       2008        - free -  (1.0M)
> >        2048        448     1  freebsd-boot  (224K)
> >        2496       1600     4  efi  (800K)
> >        4096   33554432     2  freebsd-swap  (16G)
> >    33558528  943214592     3  freebsd-zfs  (450G)
> >   976773120          8        - free -  (4.0K)
> >
> > Then I wrote the preformatted boot1.efifat image to it, using: gpart
> > bootcode -p /boot/boot1.efifat -i 4 ada0.  You can also use dd of
> > course, but I prefer using gpart for these kinds of manipulations.
> >
> > This way, you can choose between booting in old school BIOS mode, or
> > UEFI mode.  If the UEFI mode works flawlessly, you can always decide
> > later to dump the freebsd-boot partition, and use only an EFI partition.
> >
> > -Dimitry
> >
> > P.S.: The only thing that triggers my OCD here is that the EFI partition
> > has index 4, but is physically the second.  But I can live with that,
> > until I finally delete the freebsd-boot partition. :)
>
>
> You likely want to carve out more like 50MB instead of 800k for UEFI
> partition. 800k is the minimum, but it also precludes many things you
> may need to do with UEFI applications down the line.
>
> Warner
>

Thanks guys for all the answers,  I think I will just nuke freebsd-boot and
create a smallish efi where I can place boot1.efifat as suggested by
Dimitry. If this works, I can always shrink swap if I really need to later
on.

Just out of curiosity, what other functionality will UEFI provide that
takes up 50M?

Best regards,
Fernando