kernel panic: VFS: cannot mount root filesystem

[Qweasda]

When I compile a new kernel and try to boot to it I always get this error. But, I have recompiled my kernel many different times before w/o ever getting this, though now I do every time. (tried 17 times)

I tried gentoo-sourced 2.4.19 and 2.4.20.

I really really need this updated kernel, please help as I have been battling it for 3 days.

Thanks,

[BillyD]

This is oftern caused by not having the correct filesystem options compiled into your kernel. 17 times is ALOT - maybe you should leave it alone for a day, take a few deep breaths then get back to it a bit later - it might just be some simple option that you are missing that is not allowing the kernel to boot properly.
_________________
We used to have hominid cousins that were vegetarian. The palæontological record suggests that our ancestors killed them and ate them.

[Qweasda]

Well, I guessed that since it couldn't mount it but I looked throughout the whole config a few times and through the file systems section many times, all loks good. I use ReiserFS for my root and boot partition. (yes support is compiled in my kernel)

I think the only thing I changed in this kernel was support for a DHCP server: packet socket and packet filtering.
I might have changed one or two other things, I'm not too clear. But if I did it wasn't something I was un-sure of or that was risky, i doubt.

[morrian]

What else does it say about not being able to mount the root partition? Specifically, does it have some numbers in parentheses, like (08:03) or something? That will tell you what partition it is trying to mount; maybe that is misconfigured somehow?

If you're using grub, make sure the right root partition is in /boot/grub/grub.conf. Same thing goes for lilo (except I think the conf file is /etc/lilo.conf).

If you get really desperate, check out the man page for rdev (although I doubt this is causing problems).

[Qweasda]

Alright here's the full error:

[masseya]

[Qweasda]

Well I have that in my /etc/fstab. Where/how else would I put that? I tried adding it to the end of the kernel command, and the end of the boot command, no luck.

But, I completely forgot the biggest thing to the whole problem. A week or so ago I removed my mastered hardrive (/dev/hda) and put it in an older box.
I didn't even think about mentioning that. I just now edited my /etc/fstab to change it all from /dev/hdbx to /dev/hdax since that is what it is now. I still get that error.

I just don't understand why my old kernel that was compiled before I removed the HD works, but anything after doesn't. It seems it would be just the opposite.

I'm going crazy with this. Been messing with it for the past 3 hours straight almost.
I am almost tempted to reinstall Gentoo completely just to get this new kernel, but that would ruin hours of emerges and configureations.

ahhhh

[Qweasda]

With the new /etc/fstab 9changing from hdb to hda) I get Unable to mount root fs on 03:01 now, not the same as I previously mentioned, sorry.

[noff]

Slave on the Primary IDE is hdb. Grub works in order or boot drives. I have a /hda and /hde but in grub I have (hd0) and (hd1). So you may have a /hdb but grub may now be looking for (hd0)
_________________
What Larry was saying is that if you make it too easy for programmers, then poor programmers will be able to do things best left to good programmers, and will inevitably do them poorly. Everyone will suffer in the long term as a result." - Tom Chance

[morrian]

Yes, make sure that you really have the "old" drive jumpered as the master. 03:01 is referring to /dev/hda1, so make sure that this is really what you want to mount:

merry app-editors # ls -l /dev/hda*
lr-xr-xr-x 1 root root 32 Mar 1 20:40 /dev/hda -> ide/host0/bus0/target0/lun0/disc
lr-xr-xr-x 1 root root 33 Mar 1 20:40 /dev/hda1 -> ide/host0/bus0/target0/lun0/part1
lr-xr-xr-x 1 root root 33 Mar 1 20:40 /dev/hda2 -> ide/host0/bus0/target0/lun0/part2
lr-xr-xr-x 1 root root 33 Mar 1 20:40 /dev/hda3 -> ide/host0/bus0/target0/lun0/part3
merry app-editors # ls -l /dev/ide/host0/bus0/target0/lun0/
total 0
brw------- 1 root root 3, 0 Dec 31 1969 disc
brw------- 1 root root 3, 1 Dec 31 1969 part1
brw------- 1 root root 3, 2 Dec 31 1969 part2
brw------- 1 root root 3, 3 Dec 31 1969 part3

See how the device major and minor numbers are listed as 3, 0; 3, 1; etc.? This is what the 03:01 is.

Grub is configured fine to find your kernel; otherwise the kernel wouldn't even load. The only other thing to try is adding a "root=/dev/hda3" (or whatever your root partition is) to the kernel line in grub.

And, once again, make totally sure you have the right /dev/hd?? along with the right jumper settings. Remember that hda=primary master, hdb=primary slave, hdc=secondary master, hdd=secondary slave. Also remember that "1" may not necessarily be your root partition. I belive the gentoo install doc actually has "3" being the root.

The kernel should tell you as it boots (before it tries to mount the root) what drives it sees. Mine says:

hda: ST36421A, ATA DISK drive
hda: 12596850 sectors (6450 MB) w/256KiB Cache, CHS=784/255/63, UDMA(33)

(Yeah, yeah, I know. "What kind of old, small hard drive is that?" )

Anyway, I hope some of this information helps.

[morrian]

Ok, one more thing to make sure of (although a "root=..." line should override this). Try booting from your gentoo CD or some other linux bootable CD, mount your root and your boot partition (if it is separate) and chroot into your root partition

Now try:
rdev /boot/bzImage

What does that return? It should point to your root partition, but if the kernel was compiled and then the drives were changed, it may not, which may be causing the problem.

If it is wrong, you can use rdev to change the root partition the kernel "knows" about. Check the rdev man page for details.