[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Question on 'map' and 'hide'
From: |
cr |
Subject: |
Question on 'map' and 'hide' |
Date: |
Fri, 26 Sep 2003 07:01:20 +1200 |
Not exactly a bug, more like a few points that aren't quite clear in the
manual.
(Incidentally, I did hit a nasty bug - I was trying to boot Win95 on /hdc1 by
using the 'map' and 'hide' technique, and either Grub or Win95 went and
screwed with my Linux partition on /hda5 - changed it to type Amoeba and
lost the end of it where it adjoined my /hda6 /swap partition - I see
that's been reported already on this list.Fortunately Linux gpart
(Guess Partition) rescued me. I now have my DOS/Windoze partitions on
/hda where they think they belong. It seems safer. ;)
Anyway, what the manual doesn't make quite clear is some of the
following:
map (hd0) (hd1)
map (hd1) (hd0)
swaps over /hda and /hdb
How does it do this? Write to the BIOS? And does the mapping
survive a reboot? If so, how does one cancel it when wanting to
boot straight into /hda ?
I gather, though it may fool DOS/Windows, Grub itself takes no notice of
the mapping, since
map (hd0) (hd1)
map (hd1) (hd0)
rootnoverify (hd1) still points at /hda.
Does 'hide' take notice of the mapping? That is, if I want to hide /hdb1
after I've swapped the drives with map, do I do
map (hd0) (hd1)
map (hd1) (hd0)
hide (hd0,0) (i.e. as re-mapped)
or
map (hd0) (hd1)
map (hd1) (hd0)
hide (hd1,0) (i.e. the actual drive)
I gather 'hide' toggles a bit in the partition's boot record. This
presumably survives a reboot. Does Linux etc take notice of this bit -
i.e., DOS/Win can't 'see' a hidden partition, but can Linux?
One final point that the manual doesn't state - I gather that (like DOS, but
unlike Linux) Grub ignores non-used drive 'slots' in its numbering - that
is, if I have, say, a CD-ROM in /hdb, Grub numbers drives as follows:
/hda Disk 1 (hd0)
/hdb CD-ROM --
/hdc Disk 2 (hd1)
/hdd Disk 3 (hd2)
- Question on 'map' and 'hide',
cr <=