Luciano Miguel Ferreira Rocha wrote:
On Wed, Apr 11, 2007 at 10:48:36AM -0700, Mark Hull-Richter wrote:
Are there any tools for working with and moving or copying the MBR?
My machine has 2 PATA drives (hda & hdb) and 2 SATA drives (sda & sdb). The
MBR is on hda,
Actually, its on every drive.
Not exactly, there is space for it, it's the first sector, but 512 bytes
of zeroes doesn't really qualify.
> The BIOS just boots the first it cans (by
a configurable order).
but I would like (eventually or sooner) to boot from sda
because it is two years newer, faster and, hopefully, more reliable. Even
if I don't change that, I'd like a backup MBR on sda in case hda fails (hdb
has gone sour a few times due to something in the power setup, although no
data lost and it always comes back).
In order to copy the MBR, I'd also need to edit it because the drive
configuration would be different, as well as the location of my /boot
partition.
So you don't want to backup hda's MBR to sda, you just want to also be
able to boot from sda.
In principle, you can just copy the entire hda to sda, provided that sda
is no smaller than hda. The result is a clone of the source drive, and
"it's the same size." One can then use fdisk (or similar) and resize2fs
(or equivalent) to resize the last partition. Probably.
Better, simply partition sda, copy files if you wish (tar does nicely,
google is your friend), install grub or lilo or similar. _Those_ install
a useful boot sector.
A problem with copying the first sector is that it anchors the partition
table, the first four partitions are described in it.
A problem with copying just the boot code is that it expects more
somewhere else: grub and lilo expect something within a filesystem, the
standard DOS boot sector looks for a bootable partition (and that in
turn must contain executable code in its first sector).
So, you'll need to create the extra boot partition on sda, format it,
copy /boot data to the new one, umount /boot; mount newboot /boot; and
then, depending on your boot loader:
a) lilo:
1. change boot=/dev/hda to boot=/dev/sda (in /etc/lilo.conf)
2. make sure disk=/dev/sda exists and is correct (also in /etc/lilo.conf)
3. lilo -v
b) grub:
1. make sure /boot/grub/device.map has the correct value for sda
2. change (hd0) to the sda device in /boot/grub/menu.lst
3. execute grub-install /dev/sda
Note that disk= and device.map specifies the device name on boot. If you
change the BIOS boot order to boot sda first, then sda will still be
bios=0x80 (lilo) and (hd0) (grub).
Anyway, I just recomend the creation of a boot cd with /boot and fix
/boot when the need arrives.
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Cheers
John
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