documentation of GEOM data structures needed

[Erich Dollansky]

Hi,

On Mon, 11 Nov 2013 08:19:57 -0700 (MST)
Warren Block <wblock at wonkity.com> wrote:

> On Mon, 11 Nov 2013, Erich Dollansky wrote:
> 
> > I would need a documentation of the GEOM data structure. A disk got
> > damages in a strange way during the process of backing up data. It
> > was partitioned with gpart as all my disks using the MBR schema.
> > When creating the backup, the system crashed. The disk was not
> > usable anymore. I found out that the MBR was overwritten before the
> > backup was started while the beginning of the first partition seems
> > to be ok.
> 
> MBR does not have any specific GEOM structure.  It's just a standard 
> MBR: http://en.wikipedia.org/wiki/Master_boot_record

this I knew. It points then to the container for the FreeBSD slices.
> 
> See the end of the mdconfig(8) man page for an example of using it
> and gnop(8) to skip over an arbitrary length of data at the start of
> a disk.
> 
I did not tell you the other effect I have with this disk. It boots
until FreeBSD wants to mount /. So, the loaders somehow find the kernel
etc. All seems to be there except the proper entries in the data
structures defining the container and the individual partitions.

> With that and file -s, you can attempt to find mountable filesystems
> on the whole disk.  A script would be the fastest way.  The first one 
> should be relatively easy.  After that, guessing approximate
> locations would speed it up a lot.

This is the alternative if my assumptions are wrong.

Erich