On Friday, December 27, 2013 11:08:08 am Warren Block wrote:
> On Fri, 27 Dec 2013, Mathieu Arnold wrote:
> > +--On 27 décembre 2013 10:28:07 -0500 Thomas Hoffmann <trh...@gmail.com>
> > wrote:
> > | All the examples I've seen for updating bootcode assume GPT. If one has
> > | MBR (as I do) and assuming the following basic scheme:
> > |
> > | gpart show ada0
> > | => 63 976773105 ada0 MBR (466G)
> > | 63 976773105 1 freebsd [active] (466G)
> > |
> > | gpart show ada0s1
> > | => 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
> No, the PMBR is for GPT partitioning only.
> > | where the boot code is /boot/zfsboot (rather than /boot/gptzfsboot) and
> > | ada0s1 is the slice on which FreeBSD is installed?
> > Hum, no, if you're using MBR and not GPT, you can't use gpart,
> Why not? gpart is not GPT-specific. It handles MBR and BSDlabel
> bootcode correctly.
> > you have to
> > do something aweful like this :
> > # dd if=/boot/zfsboot of=/dev/ada0 count=1
> That will overwrite the MBR partition table.
> > # sysctl kern.geom.debugflags=0x10
> > # dd if=/boot/zfsboot of=/dev/ada0 skip=1 seek=1024
> That seems dangerous. I have not tried with zfsboot, but this should be
> # 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.
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