[CentOS] sda of CentOS 4 and hda Windows dual boot possible?

[Bryan J. Smith]

Robert Hanson <roberth at abbacomm.net> wrote:
> greetings,
> since i have a test server in front of me and i have never
> tried it i request your assistance please.
> ive always been a fdisk and lilo person

Both RHEL3 and 4 come with LILO.  You can use it instead.

> i have a fresh CentOS 4 "test" install on a WD120 sata
> /dev/sda
> /dev/sda1	/
> /dev/sda2	/boot
> /dev/sda3	swap
> and it just so happens i have a old test 17Gig Maxtor PATA
> with a fresh Win98 on it from helping my father migrate
> to a newer cpu and opsys
> when i go into a fdisk /dev/hda i get this "print"
> /dev/hda1	c:	w95 fat32 lba
> /dev/hda2		w95 ext lba
> /dev/hda5	d:	w95 fat 32
> currently i can boot into the CentOS 4 install and it does
> not see the PATA drive by default unless i go into fdisk of
> course. it is not mounted.

Of course, because Linux will only mount what you tell it to
(or what the installer setup).

You can manally mount these filesystems with:  
  mkdir /mnt/c /mnt/d
  mount -t vfat /dev/hda1 /mnt/c
  mount -t vfat /dev/hda5 /mnt/d

Or did you mean the BIOS?

If so, then you must tell your BIOS to setup the ATA drive as
the booting disk (BIOS disk 80h) and your SCSI as secondary.

Now if you want to be able to choose both without going into
the BIOS, you're going to have to setup GRUB to map
(/boot/grub/device.map):
  (hd0) /dev/hda
  (hd0) /dev/sda

And you'll also need to change the grub configuration
(/boot/grub/grub.conf aka /etc/grub.conf) so anything "hd0,"
is now "hd1,", while adding a "chainloader" for "hd0,0".

And re-install grub to the ATA device:  
  grub-install /dev/hda

(you might have to do this from the rescue CD _after_ you've
changed the BIOS to boot the ATA first).

This is not straight-forward to do if you've never done it.

> or i can switch them and boot into win98, whatever is best
> for this learning test.

Windows 98 does not have support for mounting Linux
filesystems (at least not without 3rd party tools).

> ive always tried to have 2 or more (hot/cold swapouts) of
> everything client and server hardwares so i never needed
> to dual boot.

Which is highly recommended, especially with XP.
More and more XP Service Pack / Hotfixes have been using the
MBR to store hidden info, and it often overwrites GRUB.  But
when you re-install GRUB, you lose that all-important info
that XP needs to boot -- FOREVER.

> can someone show me what steps they would take using linux
> rescue to get this "test" situation to dual boot please?

I recommend _against_ it, but the above steps I gave you will
work.  Here they are again, in order:  

1.  Change your BIOS to boot ATA first
2.  Boot your Rescue CD
2a.  Change /boot/grub/device.map (BIOS-hd-dev mappings as
above)
2b.  Change /boot/grub/grub.conf (hd0->hd1, plus new
chainloader entry for hd0,0)
2c.  Re-install grub to ATA with "grub-install /dev/hda"

> i did try with "linux rescue" and was rec'v grub not found
> errors when running grub-install /dev/sda so im sure i have
> done something worng.
> also, i can make the windows pata drive primary or the
> linux sata primary so please advise what is best.

It is very, very messy to boot Windows _unless_ it is the
first boot drive (BIOS disk 80h), so I recommend you make ATA
the first device.

> maybe i didnt understand the recent thread re: dual boot
> situation.

Dual-booting on the PC is a PITA.  The PC is the absolute
worst platform for dual-booting, and MS is part of the
problem.



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