looking for a disk partition ("slice") editor

Jerry McAllister jerrymc at msu.edu
Mon Sep 22 15:29:19 UTC 2008

On Sun, Sep 21, 2008 at 09:19:40AM -0500, Scott Bennett wrote:

>      On Sun, 21 Sep 2008 09:25:19 -0400 Jerry McAllister <jerrymc at msu.edu>
> wrote:
> >On Sun, Sep 21, 2008 at 07:00:39AM -0500, Scott Bennett wrote:
> >
> >>      I would like to find a disk partition ("slice" in FreeBSD nomenclature)
> >> editor that runs under FreeBSD that is able to deal properly with logical
> >> partition entries chained from an extended partition entry in the Master Boot
> >> Record.  fdisk(8) appears to be too primitive to understand logical partitions.
> >
> >I am not clear about what you are trying to do, but fdisk should not 
> >be mucking with so-called logical partitions.   FreeBSD does not 
>      As I wrote already, I do know that fdisk(8) does not understand
> logical partitions, so forget fdisk.  I'm looking for something that
> does understand them.
> >really deal with 'logical' partitions'.    Anyway, they are more akin
>      It certainly does.  I've been using them since I first installed
> FreeBSD 5.2.1 in 2005, and FreeBSD understands them just fine.  The
> FreeBSD boot loader is another matter, but it's probably not big enough
> to be that smart.
> >to FreeBSD partitions than slices.   Slices are the primary division
>      No, they are not.  They exist because the design for the Master Boot
> Record only has four entries, which originally limited one to having no
> more than four disk partitions.  

Yes, of course, there is some reason there are four and that reason is
almost always because a table somewhere has been allocated with only
room for those.    

Yes, all divisions that are made on a disk are logical - even sectors
and cylyndars in some sense.

And below, yup, just what we all said.   The slices are subdivided in 
to other logical divisions.    Yes, FreeBSD can talk to MS type logical 

But, they don't exactly mix.   A MS logical partition doesn't fit
in a FreeBSD slice being used as a FreeBSD slice.


> If one needs more partitions than four,
> then one must use one of the four MBR entries as an entry for the Extended
> Partition, which anchors a chain of small descriptors that each contain
> a) a logical partition entry and b) a pointer to the next descriptor in
> the chain.  A disk partition that has a type of 165 (IIRC) is a FreeBSD
> slice.  It matters not whether that partition is a primary partition or a
> logical partition.  The kernel is smart enough to understand the logical
> partition chain.
> >and partitions are the subdivisions.    fdisk handles creating slices 
>      A FreeBSD partition is a subdivision of a FreeBSD slice, which is
> just a disk partition, either primary or logical, of type 165.
> >and MBRs.  For partitions you use bsdlabel and it handles the boot
> >record that the MBR hands control off to.
> ...

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