Re: boot selector and extended partitions

[Alan Barrett <apb%cequrux.com@localhost>]

On Wed, 01 Feb 2012, Mark Davies wrote:
> Partition table:
> 0: Dell PowerEdge Server utilities (sysid 222)
>    start 63, size 433692 (212 MB, Cyls 0-26)
> 1: NTFS, OS/2 HPFS, QNX2 or Advanced UNIX (sysid 7)
>    bootmenu: Windows
>    start 434176, size 204800 (100 MB, Cyls 27/6/44-39/197/30), Active
> 2: NTFS, OS/2 HPFS, QNX2 or Advanced UNIX (sysid 7)
>    start 638976, size 41738240 (20380 MB, Cyls 39/197/31-2637/219/14)
> 3: Ext. partition - LBA (sysid 15)
>    start 42377216, size 270200832 (131934 MB, Cyls
> 2637/219/15-19457/21/20)
> Extended partition table:
> E0: Primary DOS with 32 bit FAT (sysid 11)
>    start 42379264, size 4194304 (2048 MB, Cyls 2637/251/47-2899/17/62)
> E1: NetBSD (sysid 169)
>    bootmenu: NetBSD
>    start 46573631, size 266004417 (129885 MB, Cyls
> 2899/17/63-19457/21/20)
> Bootselector enabled, timeout 10 seconds.
> First active partition: 1
> Drive serial number: 1744830464 (0x68000000)
>
>
> but if I try and boot I only get a menu comprising
>  1. Windows
>
> no NetBSD.  Is this because NetBSD is in an Extended partition?

I think that mbr_bootsel does not allow booting from extended
partisions, but mbr_ext does.  (See mbr(8).)  In order to make
space for the extra code needed for scanning extended partitions,
mbr_ext sacrifices the ability to use CHS disk addressing (as
opposed to LBA disk addressing).

--apb (Alan Barrett)