How to restore FreeBSD boot manager on GPT disk ?

[Warren Block]

On Tue, 8 Nov 2016, Ian Smith wrote:

> In freebsd-questions Digest, Vol 649, Issue 3, Message: 3
> On Tue, 8 Nov 2016 10:49:23 +0000 Manish Jain <bourne.identity at hotmail.com> wrote:
>
> > One thing I have loved about FreeBSD over the years is the superbly
> > designed Boot Easy boot manager. If any other OS overwrites the MBR, it
> > is straightforward to restore with 'boot0cfg -B /dev/ada0'
> >
> > That command only works on MBR disks though, as far as I know. Is there
> > any equivalent command on a GPT disk ?
>
> Sadly, no.  Noone has written a GPT equivalent of boot0cfg; perhaps it's
> too hard, or developers perceive no use for multi-booting; I don't know.
>
> Often people will suggest using the GPL'd GRUB; I suppose that works ok
> with GPT disks these days.  You could research rather more complicated
> Boot Environments, about which I know nothing, but I don't think these
> enable a choice between e.g. BSD/s|Linux/s|Window/s systems as boot0cfg
> does.  [ Corrections to any misperceptions are welcome! ]
>
> Jack L. offered:
>  gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 ada0
>
> which restores the PMBR and GPT bootblocks to ada0p1, but that's not
> (yet?) able to provide or restore multi-boot options as such.
>
> Are you forced to use GPT, because of UEFI-only motherboards?

If the machine is booting in BIOS from a GPT disk, it *should* work to 
put boot0 on there, replacing the PMBR.  I think, anyway, have not 
tested it.