Re: Cannot boot from SATA drive

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Ed Kim wrote:
> 
> Good advice, but regarding the question if the SATA drive isn't listed
> as a boot device in the BIOS, AFAIK it wouldn't prevent the MBR from
> being written to the SATA drive.  As long as your configured your GRUB
> to be installed on the SATA drive MBR during install, it shouldn't
> matter if it was set as the boot drive in the BIOS at that time.
> 
The problem is not that the SATA is listed as a boot device or not.
It is that the BIOS device number is different when it is the boot
device. The device.map file that Grub uses when it does the install
has to match the configuration that Grub will be booting under. So
do the numbers in the grub.conf file. Unless you tell it otherwise,
in a case where you booted off of /dev/hda Grub is going to map that
as hd0. In this case, the IDE drive is hd0 and the SATA drive is
hd1. But when you change it so that the SATA drive is the boot
drive, then it is hd0.

Remember, Grub has to use BIOS mapping of drives in stage 1. Once
stage 2 (or stage 1.5) is loaded, it can access the file system, but
because stage 1 must fit in the MBR, it ends up being dumb. So the
device.map file used during install must match the configuration
that Grub will be booting under.

It does make sense for things to work this way most of the time. It
lets you install more then one OS on the same drive. You can chain
boot loaders with a second boot loader on the second drive. It is
only when you are planning on changing drive order after the install
that you need to do some extra work to make things boot correctly.

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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