dd copy of FreeBSD-7.2 won't boot

[jflowers]

I wound up using kraduk's suggestion except for using a snapshot instead of a
live file system.  Because the source disk had suffered DMA errors and a few
files lost to SOFT UPDATE errors, I built a full system first and then let
rsync merge the two.

mount -u -o snapshot /snapshot/snap1 /
mdconfig -a -t vnode -f /snapshot/snap1 -u 4
mount -r /dev/md4 /mnt
mount /dev/ad4s1a /mnt_t
rsync -aPH --exclude=usr/dumps/** /mnt/* /mnt_t
umount /mnt
mdconfig -d -u 4
umount /mnt_t

repeated for all partitions (/ /tmp /var /usr).

Also had to edit transferred fstab to reflect new device name (ad4) and
install a new boot0.

mount /dev/ad4s1a /mnt_t
vi /mnt_t/etc/fstab
umount /mnt_t

fdisk -B -b /boot/boot0 /dev/ad4

18 GB took about 20 minutes to complete snapshots and another 25 minutes to
transfer via rsync.

Thanks for all the help.

On Thu, 25 Jun 2009 10:49:50 -0500, Rick C. Petty wrote
> On Wed, Jun 24, 2009 at 11:11:21PM +0100, krad wrote:
> > Personally id stay away from dd. Create the partitions and file systems
> > manually, and install the boot loader, then rsync the data across. It will
> > be a lot faster in most cases, as unlike dd you wont be copying unused
> > space. Something like this should do the job
> 
> I wouldn't say rsync is faster than dd, unless you have a lot of 
> empty space or are migrating across a network.  The nice thing about 
> rsync is it if you restart it, it picks up where it left off so to 
> speak.  With dd you have to add two arguments.
> 
> > Rsync -aPH --exclude=/mnt/** / /mnt
>   ^
> 
> I often use:
> 
> 	rsync -avHSPx / /mnt
> 
> The "x" means don't cross file system boundaries, which is generally 
> what you want when migrating file systems.
> 
> > I'm assuming you weren't migrating due to a bad disk
> 
> Actually using rsync to migrate a bad disk is preferrable over dd
> 
> (presuming you have no backup), since rsync will skip and warn you aboud
> bad files, but "dd conv=noerror" could leave you in a bad situation 
> if it skips over critical metadata blocks.  I always try rsync first,
>  with the source filesystem mounted read-only, and if that fails 
> I'll fall back to dd.  Actually if you have the space and it was a 
> bad disk, I'd probably dd to a new disk or file, then mount that 
> disk or file read-only, and then use rsync.
> 
> -- Rick C. Petty
> 
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--
Jim Flowers <jflowers at ezo.net>