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Re: Upgrade procedure/advice: boot sector





Don Levey wrote:

I decided that, given a slow weekend, I would upgrade my personal
mail/web server from RedHat9 to Fedora2.  Wanting to minimise problems,
I did what I hoped would a complete, sector-for-sector copy of the main
disk onto another disk of the same geometry using:
       dd if=/dev/hda of=/dev/hdb

This seems to have worked.  However, the second hard drive does not
appear to have a boot sector.  That is, when I try to boot from it I get
messages saying that I am unable to do so (I'd get the exact message,
but I need the old disk up right now so I can send this message...).

I figured that I simply needed to install the boot loader, and found
some instructions for installing grub at http://geodsoft.com/howto/dualboot/grub.htm
Basically, this involved booting to a rescue CD, running grub, finding
the stage1 file to confirm the device/partition, running the 'root'
command, and then 'setup'. This looked like it had succeeded.


However, I still can't boot from the disk.  All the files seem to be
there; that is, the copy looks like it succeeded.



This may be because you said you did a "sector-for-sector copy of the main disk onto another disk of the same geometry using: dd if=/dev/hda of=/dev/hdb"
This should always work *IF AND ONLY IF* the drives are exactly the same geometry. That means same physical construciton, and even same make, model, (and maybe even same firmware levels). If the geometry is not exactly the same it *MAY* work. What you in effect have done is create an exact *byte-for-byte* copy of the drive, including boot sector, partiton table, and even the otherwise inaccessible data that handles LBA mapping, etc. If this changed information happens to be incompatible with the new hardware it can fail; particularly if the boot sector is not where the drive firmware expects it to be.


I assume from what you have said, that the drive is accessible in all ways /except that it will not boot/. As such I would suspect a geometry problem that confuses the drive firmware during boot and before Linux gets loaded.

Should I:
1) Just boot to the Fedora CDs and run the upgrade? Would this install
the boot loader for me? Or...
2) Work harder at getting the new disk to boot first, and then do the
upgrade?


Maybe you should rewrite the partiton table on the new drive and then copy partiton-by-partition to that drive.

Thanks in advance,
-Don








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