Grub Error 21 Reinstalling OS or Edit MBR

[devils casper]

Which version of Ubuntu are you installing? Ubuntu 7.04 has an option to specify location of GRUB.
Plug in External HD, boot up from Ubuntu CD and open Terminal. Execute this

sudo fdisk -l

Post output here.

[nb123]

I downladed the alternate copy of ubuntu, used the text based installer, and it worked great! I managed to boot ubuntu successfully from my external HDD with Grub on the External HDD, avoiding my internal hdd.

However, when I installed backtrack to the second partition and selected to boot from USB at startup, it didn't give me any options for booting (no ubuntu option) and instead loaded the LILO bootloader!!! Then, the kernel went into a state of panic, cos it couldn't find RAM and other problems like opening root device... I've tried to read up on how to solve this. From what I understand, what I need to do is: ---

1) delete the ubuntu and backtrack partitions again
2) recreate the partitions
3) install ubuntu with grub on the external hdd as before
4) install backtrack but this time when I install, only write the backtrack files, but don't write to MBR
5) Manually edit grub menu.lst file in my /boot folder in ubuntu as follows: --

title backtrack 2
root (hd0,3)
kernel /boot/vmlinuz ro root=/dev/hda3 vga=791
initrd /boot/splash.initrd

I believe the vga parameter is resolution right, I think I'll just leave this out, is that ok? How does this all sound, I really hope the installation works this time

[MrUmunhum]

I downladed the alternate copy of ubuntu, used the text based installer, and it worked great! I managed to boot ubuntu successfully from my external HDD with Grub on the External HDD, avoiding my internal hdd.

However, when I installed backtrack to the second partition and selected to boot from USB at startup, it didn't give me any options for booting (no ubuntu option) and instead loaded the LILO bootloader!!! Then, the kernel went into a state of panic, cos it couldn't find RAM and other problems like opening root device... I've tried to read up on how to solve this. From what I understand, what I need to do is: ---

1) delete the ubuntu and backtrack partitions again
2) recreate the partitions
3) install ubuntu with grub on the external hdd as before
4) install backtrack but this time when I install, only write the backtrack files, but don't write to MBR
5) Manually edit grub menu.lst file in my /boot folder in ubuntu as follows: --

title backtrack 2
root (hd0,3)
kernel /boot/vmlinuz ro root=/dev/hda3 vga=791
initrd /boot/splash.initrd

I believe the vga parameter is resolution right, I think I'll just leave this out, is that ok? How does this all sound, I really hope the installation works this time

There are many questions you need to answer here:
1) How are you booting from the external HD? From a BIOS options?
2) Do you have Grub installed on your external HD?
3) What is backtrack, an OS?

The root entry in Grub is being directed to the drive that your have booted from.
It is pointing to the 3rd partition, if that is an external drive then the kernel
record should point to /dev/sdaX not /dev/hda3.

This may help you: USB Boot using GRUB

Grub is a great tool but sometimes it can be a pain to configure.

[devils casper]

what I need to do is: ---

1) delete the ubuntu and backtrack partitions again
2) recreate the partitions
3) install ubuntu with grub on the external hdd as before
4) install backtrack but this time when I install, only write the backtrack files, but don't write to MBR
5) Manually edit grub menu.lst file in my /boot folder in ubuntu as follows: --

title backtrack 2
root (hd0,3)
kernel /boot/vmlinuz ro root=/dev/hda3 vga=791
initrd /boot/splash.initrd

I believe the vga parameter is resolution right, I think I'll just leave this out, is that ok? How does this all sound, I really hope the installation works this time

Correct. but you might have backtrack boot up problem. You have to enter correct kernel and initrd names in menu.lst file of Ubuntu.

In case it doesn't work, boot up Ubuntu, mount BackTrack / partition and execute this

ls  <backtrack_root>/boot

Post output here.

Good Luck !

[nb123]

Mr. Umunhum, yes, my bios supports USB emulation, grub's installed on my external USB hard disk and backtrack is a linux distro

Okay, I did all the steps I said I was going to do and managed to boot ubuntu, edit the menu.lst to see backtrack 2 in the boot options, but unfortunately I'm still unable to boot backtrack 2.

devils_casper, I ran 'ls /backtrack/boot', and these are the files in the boot folder: ---

splash.bmp
splash.initrd
vmlinuz

which means my specifications in menu.lst for backtrack kernel and booting are correct right? Then there must be something wrong with the way I'm referring to the kernel, because I get the following error message: ---

RAMdisk: couldn't find valid ram disk image starting at 0
VFS: Cannot open root device "sdb3" or unknown-block (0,0)
Please append a correct "root=" boot option
Kernel panic - not syncing : VFS: Unable to mount root fs on unknown block (0,0)

Mr. Umunhum - I looked up how I was supposed to address the kernel, as in the root = /dev/hda3 part and apparently that is the way to do it, however, I tried your way as well, but was unable to get it to boot, I got the same error message I just mentioned. So far I've tried these - sda3, sdb3, hda3

So now I'm really confused as to how I'm supposed to refer to it. Just for the record, this is what I've been putting in the menu.lst : ---

title backtrack 2
root (hd0,2)
kernel /boot/vmlinuz ro root=/dev/hda3
initrd /boot/splash.initrd

I'm doing it like this because the backtrack operating system is on my USB external hard disk, the only other hard disk I have, and on the 3rd partition within it. From what I've read, root (hd0,2) should be correct, since backtrack does begin to boot right? But then what should I put in "root =/dev/????"

Also, I have 1 last question to ask. By the way, thanks guys for being so helpful, I can't wait to play around with Beryl effects! I'm so close!! Okay, I think I'm gonna put this in another thread because other people may have this same problem and I'm not really sure how to search for answers to this online , so hopefully your help will help others like me too... Please refer to the new thread : ---- " Recognize GRUB on bootable USB Hard Disk when Power on "

[devils casper]

title backtrack 2
root (hd0,2)
kernel /boot/vmlinuz ro root=/dev/hda3
initrd /boot/splash.initrd

Remove initrd line and in case it doesn't work, post the output of fdisk -l command here.

[nb123]

I removed the initrd line, and it still didn't work. Here's the output of fdisk -l in ubuntu -

Disk /dev/sdb: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 1 1245 10000431 83 Linux
/dev/sdb2 1246 1494 2000092+ 82 Linux swap / Solaris
/dev/sdb3 1495 2102 4883760 83 Linux
/dev/sdb4 2103 9727 61247812+ 5 Extended
/dev/sdb5 2103 3347 10000431 83 Linux
/dev/sdb6 3348 9727 51247318+ b W95 FAT32


I'm not sure but could this problem be related to the LILO bootloader that backtrack installed in it's own partition, at least that's what I think happened, because I saw it during installation. Maybe I have to use chainloader or something to load LILO? How do I do this? I just saw another thread where you responded to another person doing the exact same thing as me, Ubuntu and Backtrack 2, you told him to remove the initrd line, and it worked for him, why is it not working for me, so strange...

[nb123]

I tried using chainloader by typing

rootnoverify (hd0, 2)
kernel.....
initrd.....
chainloader +1

but that didn't work as well, so then I found my UUID of the partition on which backtrack is installed, and I edited the menu.lst again, this time using the UUID, and still it couldn't be found. This leads me to think that my installation is faulty? I don't know what else to do, the UUID should not fail right? It still says it cannot open root device "UUID = ...."

[devils casper]

According to output of fdisk -l, Disk name is sda.

 kernel /boot/vmlinuz ro root=/dev/sda3

[nb123]

you mean sdb3 right? But this didn't work either, Oh well, will just have to recreate backtrack partition and reinstall, see how this works... I logged into ubuntu, but apparently gparted is not compatible with my system (i386)... so I'm gonna use the liveCD I guess? I'll tell you how it goes, I really hope it works this time...