Zero-Fill format before installation

[Jeremy Chadwick]

On Tue, Oct 28, 2008 at 10:21:00AM +0000, Bullet 446 wrote:
> I have a remote machine with KVM access that I'd like to format and
> reinstall FreeBSD 7.0. I've succeded in formatting /dev/ad6 but not the main
> drive, /dev/ad4.
> Is it possbile to zero-fill format during the installation instead of simply
> deleting and recreating partitions?
> 
> I've tried booting into single user mode without any success:
> # umount -a
> umount: /cdrom: not a file system root directory
> umount: /var: not a file system root directory
> umount: /usr: not a file system root directory
> umount: /tmp: not a file system root directory
> # dd if=/dev/zero of=/dev/ad4
> dd: /dev/ad4: Operation not permitted

You need to tell GEOM to allow you to overwrite the MBR at the start
of the disk.

sysctl kern.geom.debugflags=16 then do the dd again.

I STRONGLY recommend you add "bs=64k" to that dd statement, or else it's
going to take a million years.  :-)

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |