Date: Fri, 27 Dec 2013 11:34:34 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: Warren Block <wblock@wonkity.com>, Mathieu Arnold <mat@freebsd.org>, Thomas Hoffmann <trh411@gmail.com>, freebsd-stable@freebsd.org Subject: Re: FreeBSD 10.0-RC3 Now Available Message-ID: <201312271134.34266.jhb@freebsd.org> In-Reply-To: <alpine.BSF.2.00.1312270859430.32365@wonkity.com> References: <20131226162521.GK2009@glenbarber.us> <38B0C411B75D7482B92033D2@ogg.in.absolight.net> <alpine.BSF.2.00.1312270859430.32365@wonkity.com>
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On Friday, December 27, 2013 11:08:08 am Warren Block wrote: > On Fri, 27 Dec 2013, Mathieu Arnold wrote: >=20 > > +--On 27 d=C3=A9cembre 2013 10:28:07 -0500 Thomas Hoffmann <trh411@gmai= l.com> > > wrote: > > | All the examples I've seen for updating bootcode assume GPT. If one h= as > > | MBR (as I do) and assuming the following basic scheme: > > | > > | gpart show ada0 > > | =3D> 63 976773105 ada0 MBR (466G) > > | 63 976773105 1 freebsd [active] (466G) > > | > > | gpart show ada0s1 > > | =3D> 0 976773105 ada0s1 BSD (466G) > > | 0 943218736 1 freebsd-zfs (450G) > > | 943218736 33554369 2 freebsd-swap (16G) > > | > > | would the equivalent bootcode statement be: > > | > > | gpart bootcode -b /boot/pmbr -p /boot/zfsboot ada0s1 >=20 > No, the PMBR is for GPT partitioning only. >=20 > > | where the boot code is /boot/zfsboot (rather than /boot/gptzfsboot) a= nd > > | ada0s1 is the slice on which FreeBSD is installed? > > > > Hum, no, if you're using MBR and not GPT, you can't use gpart, >=20 > Why not? gpart is not GPT-specific. It handles MBR and BSDlabel=20 > bootcode correctly. >=20 > > you have to > > do something aweful like this : > > # dd if=3D/boot/zfsboot of=3D/dev/ada0 count=3D1 >=20 > That will overwrite the MBR partition table. >=20 > > # sysctl kern.geom.debugflags=3D0x10 > > # dd if=3D/boot/zfsboot of=3D/dev/ada0 skip=3D1 seek=3D1024 >=20 > That seems dangerous. I have not tried with zfsboot, but this should be= =20 > close: >=20 > # gpart bootcode -b /boot/zfsboot ada0 > # gpart bootcode -b /boot/zfsboot ada0s1 No, the ZFS MBR bootstrap doesn't use the "standard" boot block areas. The only "standard" boot block area for ada0 is the MBR itself, but ZFS uses a larger bootloader that installs one part into the MBR and another part a few sectors later in the disk. gpart has no knowledge of that AFAIK. =2D-=20 John Baldwin
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