[clug] Horrifying experience

Darren Freeman daz111 at rsphysse.anu.edu.au
Thu Aug 14 10:47:06 EST 2003


I'm just recovering from one of the worst IT disasters I've been in.

I was installing Mandrake 9.1 over RedHat 7.3 All was going fine but I
left for an hour when the installer was installing the RPMs.

The owner then finished off the install by accepting all the defaults,
in my absence. I hate it when that happens, as I then have to hunt for
all the settings that have dumb values. Well this time it was the
bootloader settings that killed me - it has to install LILO on the first
drive and boot linux off the second one. But the settings were set to
GRUB off the first drive entirely. (probably someone else I know of
popped in to do that).

The system was then unbootable. No worries, just use a linux boot CD
(mandrake 9.1 install), and fix the problem. Nup. I tried and tried and
tried, I couldn't get Windows XP to boot. Retrospectively it was because
LILO was installing itself to the start of the first partition, rather
than the start of the disc.

I managed to remove the Linux bootloader using the rescue GUI from
Mandrake. This probably restored a stale backup from a previous drive
partition geometry as C: was now toast. Garbled to hell. I deleted and
re-added the partition (it was the whole drive so not as risky as it
sounds). Now C: was empty.

I hunted on Google and a couple of people (including an M$ apology for
their CHKDSK programme not doing this) suggested that sector 6 of a
FAT32 partition is a backup of sector 0, the boot sector. So I booted
off the Mandrake CD, and used dd to copy sector 6 over sector 0 (praying
the definition of sector is the same as the definition of block used by

It worked. I mounted the partition and saw everything where it should
be. I rebooted. XP booted. I said something profane loudly, and was
quizzed upon what was going on. That was the closest I have come to
wiping a colleague's data and coming out with a fixed system.

Once I worked out the LILO config problem I got everything back to
normal. I had to use the above trick again in the process of finding the

So the moral to the story is: a) when installing a Linux distro for
someone who needs help on the first half of the installer, don't leave
them alone to do the disc-feeding, and b) remember to copy sector 6 over
sector 0 if you have totally borked a FAT32 partition and have no other

Have fun,

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