How to mirror the FreeBSD OS on two disks

[Warren Block]

On Thu, 12 Jul 2012, Wojciech Puchar wrote:

>>> 
>>> I am no expert at this however a quick Google search comes up with:
>>> 
>>> http://www.freebsd.org/doc/handbook/geom-mirror.html
>> 
>> The procedure shown there produces a mirror that will not boot on FreeBSD 
>> 9.
>
> no idea but my procedure certainly would work if you use installer
>
> 1) install to first disk
> 2) gmirror label system /dev/seconddisk
> 3) bsdlabel -w /dev/mirror/system
> 4) bsdlabel -e /dev/mirror/system - make partitions as required.
> 5) bsdlabel -B /dev/mirror/system
> 6) newfs all created partitions (/dev/mirror/systema etc...)
> 7) add
>
> vfs.root.mountfrom="ufs:mirror/systema"
>
> to loader.conf
>
> edit /etc/fstab and change all things to new places
> 8) mount and copy files using tar or dump/restore to new place
> 9) reboot. system will start from gmirror
> 10) gmirror insert system /dev/firstdisk
>
> all done.
>
> if installer is not used but bootable media with complete system, just create 
> gmirror then as usual.

The current Handbook procedure avoids the copy by using the existing 
disk as-is and just writing the gmirror metadata to the last block.  If 
that last block is already part of an MBR partition, the more strict 
checking stops booting in 9.0.