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Date:      Tue, 8 Nov 2016 07:46:00 -0700 (MST)
From:      Warren Block <wblock@wonkity.com>
To:        Ian Smith <smithi@nimnet.asn.au>
Cc:        Manish Jain <bourne.identity@hotmail.com>, freebsd-questions@freebsd.org
Subject:   Re: How to restore FreeBSD boot manager on GPT disk ?
Message-ID:  <alpine.BSF.2.20.1611080742440.74332@wonkity.com>
In-Reply-To: <20161108231123.T41537@sola.nimnet.asn.au>
References:  <mailman.140.1478606402.80500.freebsd-questions@freebsd.org> <20161108231123.T41537@sola.nimnet.asn.au>

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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@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.



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