Re: Keeping NetBSD disklabel up to date

[Wolfgang Solfrank <Wolfgang%Solfrank.net@localhost>]

Hi,

Michael van Elst schrieb:
> beaker%sdf.org@localhost writes:
>
> > So it sounds like mbrlabel by itself would not have been sufficient for
> > avoiding this scenario; it's output still needs to be applied via the
> > disklabel tool; is that correct?
>
> Yes.

No, this is not fully correct. See below.

> > I'm sort of surprised as the mbrlabel(8)
> > manpage says
>
> >   "mbrlabel is used to update a NetBSD disk label from the Master Boot
> >    Record (MBR) label and Extended Boot Record (EBR) label(s) found on
> >    disks that were previously used on DOS/Windows systems (or other MBR
> >    using sys tems)."
>
> > Perhaps it's grammatically correct but not literally correct -- it is
> > used to update the disklabel but doesn't actually do it itself?
>
> mbrlabel does the following:
>
> - read the current disklabel from disk
> - enumerate the MBR partitions, for each partition

Note that this includes any extended partitions on the disk.

>    - ignore if a disklabel entry with the same offset and size exists.
>    - ignore if a disklabel entry exists that overlaps
>    - otherwise add a corresponding disklabel entry

Just for the record, there has to be space in the disklabel for the
new entry.

> - with -w option, write back the modified disklabel to disk

No, the -w options updates the in-core disklabel only.  You'll
have to add a -r as well in order to write the label to the disk, too.

> So the best thing that can happen is that the modified partitions
> are appended. But usually it will just clash with with a previous
> entry.
>
> You can remove the previous disklabel entries for the non-NetBSD
> partitions, and then run mbrlabel -w to append the new entries.
>
> Or you can run mbrlabel (without -w) and replace the previous entries
> accordingly.

No, without -w, mbrlabel will just print out the modified disklabel,
but will neither change the in-core label nor the one on disk.

Ciao,
Wolfgang
--
Wolfgang%Solfrank.net@localhost				Wolfgang Solfrank