Re: FreeBSD 10.0-RC3 Now Available

From: Warren Block <wblock_at_wonkity.com>
Date: Fri, 27 Dec 2013 09:08:08 -0700 (MST)
On Fri, 27 Dec 2013, Mathieu Arnold wrote:

> +--On 27 décembre 2013 10:28:07 -0500 Thomas Hoffmann <trh411_at_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 
close:

   # gpart bootcode -b /boot/zfsboot ada0
   # gpart bootcode -b /boot/zfsboot ada0s1

Untested!  The first one may need to use /boot/mbr.  A better way to do 
this, provided the system does not have a broken BIOS, would be to 
backup, repartition with GPT, and restore, avoiding the complication of 
multiple partitioning schemes.
Received on Fri Dec 27 2013 - 15:08:11 UTC

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