Re: Grub question

[Felix Miata]

On 2008/07/22 17:26 (GMT-0700) walt apparently typed:

> Now, just to confuse you further, Felix has a good point:  I recall from
> decades past (not past enough!) that the ordinary DOS mbr will boot the
> partition marked *active*, even if it's (M$ forbid!) not Windows.

> If you now install grub to your linux partition, lets say (hd0,5) instead
> of (hd0), for example, and then use fdisk to mark that partition 'active',
> even the old DOS mbr *should* then start grub running instead of Windows.

> Felix, am I remembering all of this correctly?  Is it still true for the
> mbr installed by XP or Vista?  (I don't intend to experiment ;o)

Almost. "Standard" MBR code will transfer control to ("boot") the PBR of
whichever *primary* partition is marked "active" on the first BIOS HD. I
believe this can include placement of Grub in the PBR of and setting "active"
the extended, but I've never tried it.

By "standard" I mean legacy MS/PC DOS MBR code from the early '80's, or its
progeny. The original MBR code cannot see past cyl 1023, so "standard" code
installed by windoz (circa 95B IRRC) is slightly modified to include INT13X
extensions, enabling booting anything within reach of INT13X. I don't know
whether that includes LBA48 or not, or if a yet newer version of "standard"
code is further modified to include that too.

This means standard MBR code can start Grub on e.g. (hd0,2), from which via
menu.lst or a prompt Grub can either chainload any partition anywhere,
including windoz on say (hd0,0), load a memtest binary, load an installation
kernel and initrd, load a standard kernel and initrd, or any of several other
things.

I've never installed Vista. I've never installed Grub to any MBR
intentionally, and when done by accident, always replaced it with standard
MBR code. By not depending on it, I know I can always boot whatever I want
regardless whether windoz slipstreams something new into the MBR, or never
touches it at all.
-- 
"Do not let the sun go down while you are still angry."
                                Ephesians 4:26 NIV

 Team OS/2 ** Reg. Linux User #211409

Felix Miata  ***  http://fm.no-ip.com/