Bootable partitions

[Ben Scott]

On 3/13/06, Paul Lussier <p.lussier at comcast.net> wrote:
> Does anyone know if actually marking a partition as "Bootable" really
> matters?

  You neglect to mention the hardware platform.

  Assuming you're talking the IBM-PC: There is no "bootable" flag.

  There is a flag for the active primary partition.  The active
primary partition is the partition which gets booted by any standard
MBR.  The BIOS loads the MBR (Master Boot Record -- the first block on
the disk).  The MBR looks at the partition table, finds the active
primary partition, loads the PBR (Partition Boot Record -- first block
in the partition) from it, and jumps into that.

  You're only supposed to have one active partition at a time, but I
expect most implementations just boot the first one they find, so
having more probably won't prevent you from booting, but also won't do
you any good.  Plus, most partition tools will see multiple active
partitions as an error (which is is, really) and fix it for you.

  The partition type should be totally ignored by a standard MBR. 
(Well, it might object to trying to boot a type 0 (unused) partition.)

  If you have LILO or GRUB installed in place of the standard MBR, the
"active" flag is totally ignored, and the boot loader config file
takes over.

> Unfortunately, FAI only allows for
> a single partition to be marked as "Bootable".

  I'd guess FAI is using "bootable" to mean "active primary", but
that's just a guess.  What does FAI's "bootable" actually translate to
in IBM-PC terms?

-- Ben