Subject: Re: A new partition handling scheme: wedges
To: Ignatios Souvatzis <ignatios@theory.cs.uni-bonn.de>
From: Manuel Bouyer <bouyer@chassiron.ensta.fr>
List: tech-kern
Date: 01/26/1998 15:24:13
On Jan 26, Ignatios Souvatzis wrote
> Wolfgang writes:
> 
> > Extended partitions are just like the complete disk, i.e. they have a MBR
> > of their own and thus can have again 4 partitions.  And yes, AFAIK that's
> > the way Linux _does_ their partitioning...
> 
> No, they're even sicker.
> 
> they create a type linux-root partition for 'a', and an extended partition
> for the rest of the disk.
> 
> They create, inside that, a type linux-swap partition for 'b', and an extended
> partition for the rest of the disk.
> 
> They create, inside that, ...

Hum, They don't always do that:
chauveau#/promethee/bouyer>uname -a
NetBSD chauveau.ipv6.lip6.fr 1.3_BETA NetBSD 1.3_BETA (ANTIFER) #7: Tue Jan 13 14:12:47 MET 1998     bouyer@antifer.ipv6.lip6.fr:/usr/src/NetBSD/src/sys/arch/i386/compile/ANTIFER i386
chauveau#/promethee/bouyer>fdisk /dev/rsd0d
******* Working on device /dev/rsd0d *******
Warning: BIOS sector numbering starts with sector 1
parameters extracted from in-core disklabel are:
cylinders=3072 heads=33 sectors/track=63 (2079 sectors/cylinder)

Figures below won't work with BIOS for partitions not in cylinder 1
parameters to be used for BIOS calculations are:
cylinders=1024 heads=99 sectors/track=63 (6237 sectors/cylinder)

Information from DOS bootblock is:
0: sysid 131 (Linux native)
    start 63, size 62307 (30 MB), flag 0x0
		beg: cylinder    0, head   1, sector  1
		end: cylinder    9, head  98, sector 63
1: sysid 131 (Linux native)
	start 62370, size 617463 (301 MB), flag 0x0
		beg: cylinder   10, head   0, sector  1
		end: cylinder  108, head  98, sector 63
2: sysid 165 (NetBSD or FreeBSD or 386BSD)
    start 679833, size 1234926 (602 MB), flag 0x80
		beg: cylinder  109, head   0, sector  1
		end: cylinder  306, head  98, sector 63
3: sysid 5 (Extended DOS)
	start 1914759, size 4471929 (2183 MB), flag 0x0
		beg: cylinder  307, head   0, sector  1
		end: cylinder 1023, head  98, sector 63

So linux can also use 'flat' partitions. Maybe they improved fdisk :)
But what you've said means that linux can use extended partition inside
extended partition.

--
Manuel Bouyer, LIP6, Universite Paris VI.
email: bouyer@rp.lip6.fr
       bouyer@ensta.fr
--