Why is 'disklabel'ng a new drive so difficult?

Jerry McAllister jerrymc at msu.edu
Wed Mar 28 22:13:32 UTC 2007


On Wed, Mar 28, 2007 at 10:49:15PM +0100, RW wrote:

> On Wed, 28 Mar 2007 17:19:12 -0400
> Jerry McAllister <jerrymc at msu.edu> wrote:
> 
> > Then, the only thing wrong is that your offsets should start at 0.
> > They mean within the slice, not raw disk sector 0.
> 
> I was just looking at the bsdlable manpage, and it says:
> 
> "For partition `c', * will be interpreted as an offset of 0.  The first
> partition should start at offset 16, because the first 16 sectors are
> reserved for metadata."
> 
> I normally use sysintall for new slices, but a few days ago I edited an
> old slice to turn the old root, swap, /tmp and /var partitions into a
> single partition d for a squid cache, and I ended-up with this:
> 
> $ bsdlabel /dev/ad0s2
> # /dev/ad0s2:
> 8 partitions:
> #        size   offset    fstype   [fsize bsize bps/cpg]
>   c: 141853950        0    unused        0     0         #  ...
>   d:  5242880        0    4.2BSD     2048 16384 28552
>   f: 16777216  5242880    4.2BSD        0     0     0
>   g: 119833854 22020096    4.2BSD        0     0     0
> 
> 
> 
> I'm wondering if I should put in an offset of 16 for the d partition

I think that is only true for some old stuff in old systems.   I believe
I saw somewhere that it only is meaningful it the -A option is used.
It might also be meaningful for the so-called 'dangerously dedicated'
disk where you don't use a slice, but the raw drive.   But, I 
never start it at an offset of 16 - always 0 if my partition is
within a slice.   

////jerry

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