Happy I was, using my dual-boot FC3/WIndows laptop, when one dark and cloudy day GrUB decides that it hates me.

I hadn't altered grub.conf, hadn't touched device.map, hadn't really messed with anything. All of a sudden though, GrUB decided that it was just going to hang after the BIOS finished loading and print the word GRUB on the screen. That's it., 'GRUB' and a blinking cursur. I don't even get to the menu.

With a sigh, I went over to my neighbors house and downloaded Knoppix. Booted onto the live CD, chrooted, and examined my grub config. As I thought, everything was as I had left it. Here are the contents of grub.conf and device.map:

[root@Knoppix grub]# cat grub.conf

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You do not have a /boot partition. This means that
# all kernel and initrd paths are relative to /, eg.
# root (hd0,4)
# kernel /boot/vmlinuz-version ro root=/dev/hda5
# initrd /boot/initrd-version.img
#boot=/dev/hda5
default=3
timeout=5
splashimage=(hd0,4)/boot/grub/splash.xpm.gz
hiddenmenu
title Fedora Core (2.6.10)
root (hd0,4)
kernel /boot/vmlinuz-2.6.10 ro root=LABEL=/ rhgb quiet
initrd /boot/initrd-2.6.10.img
title Fedora Core (2.6.9-1.667smp)
root (hd0,4)
kernel /boot/vmlinuz-2.6.9-1.667smp ro root=LABEL=/ rhgb quiet
initrd /boot/initrd-2.6.9-1.667smp.img
title Windows XP
rootnoverify (hd0,1)
chainloader +1

[root@Knoppix grub]# cat device.map
# this device map was generated by anaconda
(fd0) /dev/fd0
(hd0) /dev/hda

I tried running grub-install, and I think I may have discovered the problem:

[root@Knoppix grub]# grub-install hd0
/dev/hda5: Not found or not a block device.

[root@Knoppix grub]# grub-install hda
/dev/hda5: Not found or not a block device.

And here is some further confirmation:

GNU GRUB version 0.95 (640K lower / 3072K upper memory)

[ Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists the possible
completions of a device/filename.]

grub>
root (hd0,4)

Error 21: Selected disk does not exist

grub>

Can anyone tell me what the hell is going on?

Many thanks,

Will

That is a bit odd. Did you add any new hardware? Change the internal device connections?

I had a problem with grub after something along those lines. It might not work for you, but it wouldn't hurt. Boot knoppix, chroot into your system, and execute:
That will force grub to re-verify its device mapping even though the device.map file exists. Like I said, I don't think it'll hurt anything, so it's worth a shot.

[root@Knoppix grub]# grub-install --recheck /dev/hda
Probing devices to guess BIOS drives. This may take a long time.
/dev/hda: Not found or not a block device.
[root@Knoppix grub]#


The only thing I can think of that I did was to install the ATI drivers. That involved compiling a kernel module and editing xorg.conf; none of those things should have screwed with GRUB, right?

just as a sanity check, what does fdisk -l /dev/hda produce while in knoppix?

root@ttyp1[knoppix]# fdisk -l /dev/hda

Disk /dev/hda: 60.0 GB, 60011642880 bytes
255 heads, 63 sectors/track, 7296 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hda1 1 6 48163+ 16 Hidden FAT16
/dev/hda2 * 7 5563 44636602+ 7 HPFS/NTFS
/dev/hda3 6839 7295 3670852+ db CP/M / CTOS / ...
/dev/hda4 5564 6838 10241437+ f W95 Ext'd (LBA)
/dev/hda5 5564 6708 9197181 83 Linux
/dev/hda6 6709 6838 1044193+ 82 Linux swap

Partition table entries are not in disk order
root@ttyp1[knoppix]#

Nope, they shouldn't have done a thing to grub.

The only other thing I could think to try is fsck'ing your partitions. Maybe grub is bothered by something Knoppix doesn't mind.

I'm at a loss to explain it, because you're clearly mounting the partitions through Knoppix, and that means Knoppix is capable of recognizing /dev/hda & reading/writing to it. From what grub is saying, you'd think the drive had gone bad.

I'm tempted to just fdisk the mbr and install grub from scratch, after backing up my grub.conf file of course. Anyone think this is a good idea?

It's bad form to reply to oneself, but then again -- grub-install hda already failed, so I guess my previous post was just wishful thinking.

I've never seen that message before. One thing you could try is to go into fdisk, delete your swap partition, save & exit, re-enter, recreate the swap, save & exit.

Just something to re-write the partition table without losing any data.

Ugh... I have this personal rule: No fdisking after midnight. Currently where I am it's 3 in the morning, but I guess this is an emergency...

I'll let you know how it goes.

Pray for me (and my data)

The result of my post-midnight fdisking:

Disk /dev/hda: 60.0 GB, 60011642880 bytes
255 heads, 63 sectors/track, 7296 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hda1 1 6 48163+ 16 Hidden FAT16
/dev/hda2 * 7 5563 44636602+ 7 HPFS/NTFS
/dev/hda3 6839 7295 3670852+ db CP/M / CTOS / ...
/dev/hda4 5564 6838 10241437+ f W95 Ext'd (LBA)
/dev/hda5 5564 6708 9197181 83 Linux
/dev/hda6 6709 6838 1044193+ 82 Linux swap

Partition table entries are not in disk order

Command (m for help): v
16251 unallocated sectors

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
root@ttyp1[knoppix]#

Chrooted and:

[root@Knoppix boot]# grub-install --recheck /dev/hda
Probing devices to guess BIOS drives. This may take a long time.
/dev/hda: Not found or not a block device.
[root@Knoppix boot]#

Ewww... from the warning it spat out, you may need to reboot twice:
1) After you delete the swap
2) after you recreate the swap

If the partition table is the problem, then it's no good if the kernel is using the original one.

So to summarize, so I don't screw this up, I should fdisk the swap into oblivion, reboot with knoppix, make a new swap, reboot again, and then try grub-install --recheck?

Yeah, that's the game plan I would try.

I'll keep my fingers crossed.

just a note about "Partition table entries are not in disk order"

while in fdisk, go to "x extra functionality (experts only)" and then "f fix partition order"