CentOS - Jul 2005 - Reinstall Windows but preserve CentOS

I have a computer that dual boots between Windows and CentOS. Each 
has it's own hard drive.

    I suddenly have a problem with Windows, and may need to reinstall. I 
need it for applications like After Effects, Premiere, and other things 
that I am currently in the middle of a project with.

   It seems the system has become usnstable, it's preventing me from 
continuing to work, and I may need to wipe the Windows partition clean 
and start again.

    My concern is that if I do that, I will lose the Grub boot loader 
and not be able to access CentOS again.

    How can I reinstall Windows with a clean partition, and preserve my 
dual booting?

Dave

0) make a backup.  
1) unplug the centos drive while you do the install, just to be
sure.  (warning, you may run into master-slave complications due
to this, depending how you've got things configured)
2) install windows.
3) boot from centos disk in rescue mode.  re-install grub.
I think the right syntax for this would be:
 chroot /mnt/sysimage
 /sbin/grub-install
4) you did remember to make a backup, right?

On Fri, Jul 29, 2005 at 10:49:26PM +0900, Dave Gutteridge
wrote:
> 
>    I have a computer that dual boots between Windows and CentOS. Each 
> has it's own hard drive.
> 
>    I suddenly have a problem with Windows, and may need to reinstall. I 
> need it for applications like After Effects, Premiere, and other things 
> that I am currently in the middle of a project with.
> 
>   It seems the system has become usnstable, it's preventing me from 
> continuing to work, and I may need to wipe the Windows partition clean 
> and start again.
> 
>    My concern is that if I do that, I will lose the Grub boot loader 
> and not be able to access CentOS again.
> 
>    How can I reinstall Windows with a clean partition, and preserve my 
> dual booting?
> 
> Dave
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos

danno
--
dan pritts - systems administrator - internet2
734/352-4953 office        734/834-7224 mobile

On Fri, 2005-07-29 at 22:49 +0900, Dave Gutteridge
wrote:
>     How can I reinstall Windows with a clean partition, and preserve my 
> dual booting?
Can make a Grub boot floppy with a copy of the current grub.conf - see
script at bottom, [a simpler approach is to use "grub-install
/dev/fd0"
to create a GRUB floppy, but I like having the config on the floppy -
allows modifications for different boot defaults, as well as providing a
backup] and/or make a boot CD:

# mkbootdisk --iso --device boot`uname -r`.iso `uname -r`

On my system this results in file boot2.6.9-11.106.unsupportedsmp.iso
which can then be written to CD with

# cdrecord -v -dao -eject -data driveropts=burnfree dev=/dev/hda
boot2.6.9-11.106.unsupportedsmp.iso

(all one line - watch for wraps)

Either method will let you boot back to the installed system without
going though the rescue gyrations.  Can then rewrite grub with

# grub-install /dev/hda [ or whatever boot device ]

Phil

------------------------  Cut Here  ---------------------------------
#!/bin/bash
# mkgrubdisk
#
# Written by Phil Schaffner <p.r.schaffner at ieee.org>
#  based on mkbootdisk by Erik Troan <ewt at redhat.com>

pause=yes
format=yes
device=/dev/fd0
unset verbose

GRUBDIR=/boot/grub
MOUNTDIR=/tmp/mkgrubmenu
PATH=/sbin:$PATH
export PATH

VERSION=0.1

usage () {
    cat >&2 <<EOF
usage: `basename $0` [--version] [--noprompt] [--noformat]
       [--device <devicefile>] [--grubdir <dir>] [--verbose -v]
       (ex: `basename $0` --device /dev/fd1)
EOF
    exit $1
}

while [ $# -gt 0 ]; do
    case $1 in
	--device)
	    shift
	    device=$1
	    ;;
	--grubdir)
	    shift
	    GRUBDIR=$1
	    ;;
	--help)
	    usage 0
	    ;;
	--noprompt)
	    unset pause
	    ;;
	--noformat)
	    unset format
	    ;;
	-v)
	    verbose=true
	    ;;
	--verbose)
	    verbose=true
	    ;;
	--version)
	    echo "mkgrubdisk: version $VERSION"
	    exit 0
	    ;;
	*)
            usage
	    ;;
    esac

    shift
done

[ -d $GRUBDIR ] || {
    echo "$GRUBDIR is not a directory!" >&2
    exit 1
}



if [ -e "$device" ]; then {
    [ -n "$pause" ] && {
	echo -n "Insert a"
	[ -n "$format" ] || echo -n " vfat formatted"
	echo " disk in $device."
	echo "Any information on the disk will be lost."
	echo -n "Press <Enter> to continue or ^C to abort: "
	read aline
    }

    [ -n "$format" ] && {
	[ -n "$verbose" ] && echo "Formatting $device... "
	fdformat $device || exit 0
	mkfs.msdos $device > /dev/null 2>/dev/null || exit 0
	[ -n "$verbose" ] && echo "done."
    }

    rm -rf $MOUNTDIR
    mkdir $MOUNTDIR || {
	echo "Failed to create $MOUNTDIR" >&2
	exit 1
    }
    [ -d $MOUNTDIR ] || {
	echo "$MOUNTDIR is not a directory!" >&2
	exit 1
    }

    mount -wt vfat $device $MOUNTDIR || {
	rmdir $MOUNTDIR
	exit 1
    }

    mkdir $MOUNTDIR/grub

    [ -n "$verbose" ] && echo -n "Copying $GRUBDIR
files... "
    cd $GRUBDIR
    cp -a stage1 stage2 grub.conf device.map splash.xpm.gz
$MOUNTDIR/grub
    [ -n "$verbose" ] && echo "done."

    [ -n "$verbose" ] && echo -n "Setting up GRUB...
"
    grub --device-map=$GRUBDIR/device.map --batch <<EOF
root (fd0)
setup (fd0)
quit
EOF

    [ -n "$verbose" ] && echo "done."

    umount $MOUNTDIR
    rmdir $MOUNTDIR
    [ -n "$verbose" ] && echo "done setting up
GRUB."
    echo "Edit (fd0)/grub/grub.conf to customize."
    echo "May want to use splashimage=(fd0)/grub/splash.xpm.gz"
}
else
    echo "$device does not exist"
fi

Dave Gutteridge <dave at tokyocomedy.com> wrote:
> How can I reinstall Windows with a clean partition, and
> preserve my dual booting?
Recommendation #1:

Always use your Linux Rescue Disk to boot and re-install GRUB
afterwards.

Recommendation #2:  

dd can be used to preserve and return the _full_ MBR.
I.e., the _full_ MBR is Cylinder 0,
  1 cyl * X heads * Y sectors * 512 bytes/sector

So if your disk geometry is 16/63 heads/sectors,
to preserve the 512KiB MBR:
  dd if=/dev/XdX of=./MBR.dd bs=512K count=1
to restore the 512KiB MBR:  
  dd if=./MBR.dd of=/dev/XdX bs=512K count=1 conv=notrunc

If your disk geometry is 255/63 heads/sectors,
to preserve the 8MiB MBR:  
  dd if=/dev/XdX of=./MBR8MiB.dd bs=8M count =1
to restore the 8MiB MBR:  
  dd if=./MBR.dd of=/dev/XdX bs=8M count=1 conv=notrunc

Gotcha A:  This will _also_ include the disk label
(partition table), So it _only_ works when it's a matching
replacement.

Gotcha B:  Some service packs and hotfixes for Windows NT5.1
(XP) have been stealthy using portion of the MBR for disk
geometry and other information.  This sometimes _breaks_ GRUB
and other boot loaders as they step on each other.



-- 
Bryan J. Smith                | Sent from Yahoo Mail
mailto:b.j.smith at ieee.org     |  (please excuse any
http://thebs413.blogspot.com/ |   missing headers)

Dave Gutteridge wrote:
> 
>    I have a computer that dual boots between Windows and CentOS. Each
> has it's own hard drive.
> 
good to have them on their own drives.
1. configure the windows as the master disk, install windows with the
linux disk removed.
2. add the linux disk as slave or secondary master or slave. This
assumes that grub is loaded on the MBR of the linux disk.
3. set the bios to boot from the linux disk.
4. load linux and configure grub to boot windows.

i have the same setup and works fine. do whatever you want to your
windows disk, there is no problem.

hth,
Raghavendra Moktali