Kernal panic: cannot find root device

NeddySeagoon · Posted: Fri Jul 16, 2010 10:46 pm Post subject:

sl70,

Save your .config file outside of the kernel tree, do

krinn · Watchman Joined: 02 May 2003 Posts: 7470

and try re-emerge udev and check also its version while your at it.

Maybe it's not the kernel that doesn't find your disk. But udev that doesn't create the nodes for your disk partitions.

NeddySeagoon · Posted: Sat Jul 17, 2010 10:06 am Post subject:

krinn,

When root is being mounted, udev cannot be running and /dev is not mounted ... nothing is mounted.
The kernel uses the root=/dev/... kernel parameter to work out where its root filesystem is without any outside help.

Even when an initrd is used, the kernel still has to find its root from root=/dev/... but there is normally some help provided in the initrd to be able to mount real_root=/dev/...

Edit ... late thought ...

What disk label (partition types) are you using and what does your kernel support ?
The default is MSDOS Partition tables. Which you also need in the kernel. GPT is becoming more popular and is a must have for drives over 2TB as MSDOS Partition Tables have a hard limit there.

It is possible to turn off all partition table support, with the result that the kernel cannot read your partition tables. This is a very bad thing.

Edit 2 ...
You have CONFIG_MSDOS_PARTITION=y so the defualt setting is still there.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

krinn · Watchman Joined: 02 May 2003 Posts: 7470

https://bugzilla.kernel.org/show_bug.cgi?id=15744

try pci=use_crs this is a workaround that may work

sl70 · Guru Joined: 18 Jun 2002 Posts: 455 Location: Saitama, JP

Oh, yeah. make mrproper. That sounded like a good idea to me, too. Unfortunately, it didn't help. I also tried pci=use_crs, but that was no more successful.

However, the kernel bug listing was very interesting. The report was on a Dell Precision T3400. My machine is a Dell Precision T3500. Are we sure that the patch reported in that bug listing was applied to the gentoo sources?

sadhu · n00b Joined: 12 Oct 2004 Posts: 15

I've got same exact problem. Although, I used 'make oldconfig' and didn't try configuring from scratch yet.

NeddySeagoon · Posted: Wed Jul 21, 2010 6:48 pm Post subject:

sadhu,

Did your old config work ?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

thegeezer · n00b Joined: 11 Jul 2010 Posts: 38

have you tried rebuilding the kernel without changing *anything* in the config? i mean by zcat /proc/config.gz

it may just be me but i always have a few config files named really helpful stuff like new newest and newer... and always the one that works is the last one i try, hence the genius of just using config.gz

sadhu · n00b Joined: 12 Oct 2004 Posts: 15

No it didn't work. What I did was: zcat /proc/config.gz > .config && make oldconfig
I also tried today 2.6.34-gentoo-r2 but result are the same.

NeddySeagoon · Posted: Mon Jul 26, 2010 6:25 pm Post subject:

sadhu,

unknown-block(8,51) is /dev/sdd3

The error tells that the kernel can talk to your hard drive controller but cannot read what it finds on /dev/sdd3.
Is the root filesystem in the kernel?
is /dev/sdd3 your root partition?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

m.rizz · n00b Joined: 20 Jan 2008 Posts: 6

Yeah! Resolved! It was under my big nose.

The idea from NeddySeagoon:
I search CONFIG_MSDOS_PARTITION in the kernel config:
in File systems -> Partition Types -> Advanced partition selection was unselected
Selecting it menuconfig showed the "PC BIOS (MSDOS partition tables) support" already selected.
I recompiled and rebooted and all went good.
Now in the config file there are this two rows
CONFIG_PARTITION_ADVANCED=y
CONFIG_MSDOS_PARTITION=y
in the old config there was only the second.

sadhu · n00b Joined: 12 Oct 2004 Posts: 15

afmos · n00b Joined: 30 Jun 2007 Posts: 17

I just solved the same issue when upgrading from 2.6.32 to 2.6.34. It turned out the drives were remapped what was /dev/sdc3 in 2.6.32 is /dev/sdk3 in 2.6.34

fantasma13 · n00b Joined: 15 Jul 2004 Posts: 28 Location: Europe

can you elaborate how you solved it? I have a dell workstation as well, everything above 2.6.33-r2 is broken.

I got several AHCI reset failed -5 messages (2.6.35-r5).

sl70 · Guru Joined: 18 Jun 2002 Posts: 455 Location: Saitama, JP

Tried what m.rizz posted (CONFIG_PARTITION_ADVANCED=y) but that didn't help. Since that privilege escalation bug was announced a few weeks ago, it's gotten more urgent that I upgrade to a non-vulnerable kernel. I've tried 2.6.34-r1, r6 and, today, r11. None of them will boot. Same Kernel Panic for all.

[Sigh]

sl70 · Guru Joined: 18 Jun 2002 Posts: 455 Location: Saitama, JP

I found this post in which the poster suggests using pci=nocrs. This seems to be the opposite of what krinn suggested a couple of months ago (pci=use_crs). So, I tried nocrs, and the kernel panic is gone.

However, what am I doing? Is there any danger in using nocrs?