I installed gentoo-2005.1 on my amd 64 pc and it worked well but
the performance was not so good so i tried to recompile my kernel
using genkernel and then when i rebooted i found the error
something like that root cant be mounted . I also have ubuntu amd windows xp installed on my pc . So then I started ubuntu and tried to mount root partition of gentoo but it could not be mounted and resulted
as below

wrong fs type, bad option, bad superblock on /dev/hda8, missing
codepage or other error In some cases useful info is found in
syslog - try dmesg | tail or so

my /boot is in hda6 and root is /dev/hda8

and my grub.conf file is as below
default 0
fallback1
timeout 30
splashimage=(hd0,5)/grub/splash.xpm.gz

title Gentoo Linux 2.6
# Partition where the kernel image (or operating system) is located
root (hd0,5)
kernel /kernel-2.6.12-gentoo-r6 root=/dev/hda8


splashimage=(hd0,5)/grub/splash.xpm.gz

title GNU/Linux
root (hd0,5)
#kernel (hd0,2)/vmlinuz ro real_root=/dev/hdb2
kernel (hd0,5) /kernel-genkernel-x86_64-2.6.12-gentoo-r6
root=/dev/ram0 init=/linuxrc
ramdisk=8192 real_root=/dev/hdb8 udev
initrd /initramfs-genkernel-x86_64-2.6.12-gentoo-r6



title Ubuntu, kernel 2.6.11-1-amd64-xeon Default
root (hd0,2)
kernel /boot/vmlinuz root=/dev/hda3 ro console=tty0 quiet splash
initrd /boot/initrd.img
savedefault
boot


title=Windows XP
rootnoverify (hd0,0)
makeactive
chainloader +1

If anybody has a solution for this please tell me .
Thanks in advance

which one is your primary (most used distro)? Choose this one and mount each of the other two to /mnt (do this once or mount the second distro to something like /mnt/distro2 otherwise you'll get duplicate problems, etc.) Copy the kernels and the initrd (s) from each of these into the /boot directory of your preferred distro. This is where you should boot each of your Linuxes from, if you don't have a separate /boot. (I had the EXACT same problem lately and repartitioned my disk with shared /boot and shared /home, etc)

Now you'll have to debug the menu.lst entries in grub. You can either copy them from the other two distros into your preferred distro's menu.lst or try at boot time to manually edit the boot record. Option 2 would be easier in that if it fails at this stage, it's an awful lot faster just to power down and try again. The way you do this is when grub shows the menu (e.g. Gentoo, Ubuntu, GNU/Linux (that's Debian I take it??), Windows) go down to whatever one you wish to boot and press 'e' - which lets you edit in a console setting.

You will probably have to change the initrd to where it now resides at. If you let me know which distro you want as your preferred distro, I might be able to point yu in the right direction

If the above is correct then the grub descriptor root (hd0,5) is incorrect. This transcribes as root is at drive 1 and partition 6. It should be (hd0,7) = /dev/hda8

initrd /initramfs-genkernel-x86_64-2.6.12-gentoo-r6

This needs to be in Ubuntu's /boot and also must point to it. That would mean your entryfor gentoo should contain

initrd (hd0, 2) /boot/initramfs-genkernel............

Thanx to you both but I am not even able to mount hda8 in ubuntu or even in knoppix live cd and when i try to mount hda8
as below
mount /dev/hda8 /mnt/hda8
it gives the following error

mount: wrong fs type, bad option, bad superblock on /dev/hda8,
missing codepage or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

If you cannot mount the partition using Knoppix then using Knoppix bring up a console and do e2fsck /dev/hda8 because it sounds like the partition may be corrupted.