VFS: Cannot open root device...Start Page 2[Not Solved]

littleman · Last edited by littleman on Tue Jun 21, 2005 9:44 am; edited 3 times in total

After my linux hdd-ata100 died last week, I bought a new sata drive and reinstalled gentoo.

the livecd detects the drive and I was able to install Gentoo 2005.0 without problems.

I had a look at the lspci command, and found that the livecd used the intel sata driver (ich5) so I included it in the kernel configuration.
Upon reboot, I get the message cannot open root device "sdc2" or unknown boot device.

(sda--> windows raid - sdc1--> my windows boot partition - sdc2-->gentoo partition I have a sdb but I have no idea what it is :p)

Now, a few useful details on my system: I chose NOT to create a swap partition (2gb ram) and I did NOT create a separate partition for /boot, the whole partition is formated in reiserfs in a single partition / . Last thing, my gentoo partition is at the end of my 400gb windows drive.

I've already tried many things posted in the forums, without results.
When I chroot in my new Gentoo system, there's nothing in /var/log so where can I know what is happening at boot (it just scrolls too fast to read)?

Last funny thing: the livecd mounts my raid array as sdA, and my gentoo partition as sdC, but when configuring Grub, I had to put hd0,2 as boot device...

Any Idea?
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Sven Vermeulen · Posted: Sun Jun 12, 2005 11:12 am Post subject:

Perhaps this document can help you a bit, although I need to add an answer for another cause: using a kernel that does not support the chipset...

NeddySeagoon · Posted: Sun Jun 12, 2005 11:15 am Post subject:

littleman,

The easy one first. Your raid will not be seen by linux unless you either have real harware raid, which is unlikely. You would know from the price of the plug in card or your server motherboard, so sda and sdb are the two hald of your raid.

If you do have a real hardware raid, then sdb may be a USB storage device. Its a really bad idea to have USB storage get a letter before your root filesystem, since if its not attached, gub will look in the wrong place for /boot.

hd0,2 is grubspeak for the third partiton on the first bios detected hard drive. If your raid is not visible to the bios but the individual drives are to linux, then hd0 would be /dev/sdc. hd0,2 whould then be /dev/sdc3.

You may find that hd0,1 works better if your gentoo / is on /dev/sdc2.

Some details of your raid set up and USB storage devices would help.
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Computer users fall into two groups:-
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RiBBiT · Apprentice Joined: 18 May 2005 Posts: 215 Location: Sweden

Aro you using SCSI_SATA or BLK_DEV_IDE_SATA?

I had to enable:

littleman · Posted: Sun Jun 12, 2005 11:56 am Post subject:

Thanks for the link (I've checked all that already and double checked it again after reading the doc)

About my raid system: I don't need to have it up and running yet (it'a cheap integrated peudo-raid sil3112 chip and strictly windows-related: I don't want to spend too much time on this yet. I just know that I used to use a small thing called dmraid to make it work)
About my usb system: (appart from my a usb mouse / usb webcam) I have a usb cdrom writer but it was never on when I installed my Gentoo)

Now could I have a different partition scheme with the new Gentoo system? as opposed to the livecd one? Could the partition /dev/sdc2 be called anything else in my new Gentoo system??? How would I know since I can't boot the new system :p :p :p?

Further notes: Reiserfs are included in my kernel (not as modules) but I've heard that there's been a new version of reiserfs recently. Does the kernel recognize it?
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littleman · Posted: Sun Jun 12, 2005 11:58 am Post subject:

Oh and Ribbit, that's EXACTLY the options I selected in my kernel from what I could read in the forums

(except that I've added the driver for intel ichr too in the same section)
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RiBBiT · Apprentice Joined: 18 May 2005 Posts: 215 Location: Sweden

I seem to have compiled my kernel with support for my chipset in the ATA/ATAPI/MFM/RLL support section as well. I don't know if it's useful at all, but if you have no other ideas...
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Sven Vermeulen · Posted: Sun Jun 12, 2005 1:03 pm Post subject:

Since you are using GRUB, you can try the "trial-and-error" method

When you hit GRUB, select your Linux entry and press e (for edit). Go to the kernel line and press e again.
Now, change the root= parameter to for instance /dev/sdb3 (perhaps your kernel sees it as second SCSI in line) or /dev/hda3 (in case it sees it as an IDE).
Press enter and then b to boot it.

Perhaps it works, perhaps it doesn't, sure won't hurt trying.

Sven Vermeulen · Posted: Sun Jun 12, 2005 1:05 pm Post subject:

Oh, I also forgot.

When you get that message, are you able to still scroll up in the output (Shift+PageUp)? If yes, you might find some clues as to what disks the kernel did find. For instance, mine would say

NeddySeagoon · Posted: Sun Jun 12, 2005 1:17 pm Post subject:

NeddySeagoon,

With dmraid, linux will see your raid as three devices, /dev/sda, /dev/sdb and /dev/md.. The first two are the underlying drives and the /dev/md... will be the raided partitions. Linux and Windows can both see the raid if you use dmraid. /dev/sdc will be your other SATA drive (or real scsi)

The order in which grub sees them depends on the order of detection in the BIOS.
There is a further complication depending on which version of the liveCD you have. 2005.0 and later make SATA devices appear as SCSI. Earlier liveCDs make them appear as IDE drives. Usually /dev/hde and /dev/hdg It depends on which SATA driver is in the kernel. (The SCSI one or the noe depreciated IDE one.)

Its perfectly possible to instal with a liveCD using the IDE driver, build the SCSI one in your own kernel then wonder why it won't boot. This does not affect the bios detection order.

If you are rescueing an old install, it sometimes helps to edit /boot/grub/device.map to reflect reality.
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Regards,

NeddySeagoon

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

littleman · Posted: Mon Jun 13, 2005 9:36 am Post subject:

Update:

Ok, I've edited my boot line in grub and tried all root devices (sda1 and 2 - sdb1 and 2 - sdc1 and 2, sdc2 being my boot device when I installed Gentoo). Still the same error message.

I can scroll up with shift+page up (didn't know about this command, great stuff) but it keeps bringing me to the bottom of the page when the kernel prints out a new line and when I reach the error, I can't scroll up anymore (freeze) but I do see a lot of scsi related messages in between. Unfortunately they go too quickly for me to read

Any other suggestion to read those messages?

I'm out of options :'p

(gonna try to put in the old driver in ata section of the kernel, just in case)
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Sven Vermeulen · Posted: Mon Jun 13, 2005 9:38 am Post subject:

You might be able to 'freeze' the scrolling by pressing Ctrl+S. Pressing Ctrl+Q will unfreeze it.

littleman · Posted: Mon Jun 13, 2005 1:04 pm Post subject:

I can't freeze the scrolling although I can scroll up with the livecd kernel since it pauses to ask me for the keymap.
I've tried booting with a kernel in which I included ALL low-level SATA drivers with no results.
I've read about a similar post to mine above and the guy solved his problem by 'doing udev'...if that means that he emerged udev, I've done that too, but could there be a problem with udev???

By the way, the error message is:

Kernel Panic - not synching: VFS: Unable to mount root fs on unknown -block(8,34)

Remember, I'm using reiserfs on the whole partition and the gentoo partition is at the END of the drive. Can the system still boot that? (I guess the block 8,34 means that it's not trying to boot the first sector of the disk?)
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Sven Vermeulen · Posted: Mon Jun 13, 2005 2:33 pm Post subject:

No, the error means that it does not find a device that uses a major of 8 (which is for SCSI disks) and minor 34 (which is third disk, second partition, also known as sdc2). Here, you can read that the kernel does not even find a SCSI disk.

So either the kernel does not support your SATA chipset, or it does support it but it isn't using the sd* convention for device names.

My bet would be the former. Mind rebuilding the kernel with everything compiled in instead of using modules?

littleman · Posted: Mon Jun 13, 2005 3:10 pm Post subject:

Everything was already compiled in. I thought that chipset was standard. After checking my motherboard manual, it is indeed a simple ICH5R chip (i875P chipset).
Could the drive be recognized as hdX ??? I don't see how it could, but who knows ?

I desperately need to be able to read the kernel output :'p

(ps: It's amazing how many people have almost exactly the same problem)
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nixnut · Posted: Mon Jun 13, 2005 7:04 pm Post subject:

Take a peek at your kernel config. What is the output of grep SATA /usr/src/linux/.config?
Or if you boot the livecd and mount your root partition on /mnt/gentoo, grep SATA /mnt/gentoo/usr/src/linux/.config?
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Unther · Apprentice Joined: 20 Feb 2005 Posts: 163

Probably an idiot suggestion, but has the kernel detected the SCSI system when it tries to set the root?
I had a similar problem building a linux system to boot from a USB stick, with the root on the stick.

littleman · Posted: Tue Jun 14, 2005 1:51 pm Post subject:

Unther,
part of the problem is that I cannot read what the kernel outputs when it boots :p
I just see SCSI stuff zoom too quickly for me to read, until it freezes.
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Unther · Apprentice Joined: 20 Feb 2005 Posts: 163

You could try setting up an initrd, and booting to that.

It was what I had to do when builing a system entirely on a 2GB USB stick. Otherwise, the kernel had trouble finding the root file-system, because it hadn't found the USB stick. The linuxrc script I used began with a 'sleep 10' comand!

littleman · Posted: Tue Jun 14, 2005 2:14 pm Post subject:

Nixnut:

I did a grep ata /usr/src/linux/.config (not sata, otherwise, the intel driver didn't show up :p why is it called ata by the way?)

output:

-all CONFIG_SCSI_XXX were NOT set, except

-CONFIG_SCSI_SATA=y

-CONFIG_SCSI_ATA_PIIX=y

-CONFIG_SCSI_SIL=y
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littleman · Posted: Tue Jun 14, 2005 2:16 pm Post subject:

Unther · Apprentice Joined: 20 Feb 2005 Posts: 163

It's an initial ramdisk. You configure the kernel to enable ramdisks, and to boot to one. You then need to set up a file containing an image of a small filesystem/disk, which you configure grub to load. It then contains a script to set up the desired root, do anything else needed before pivot_rooting, chrooting, and initing. If you look through the wiki, and forums, there are several good guides to help you set it up.

MickKi · Veteran Joined: 08 Feb 2004 Posts: 1173

Unther · Apprentice Joined: 20 Feb 2005 Posts: 163

littleman · Posted: Tue Jun 14, 2005 6:01 pm Post subject:

Ok still no valid answer then

Why does the livecd init everything correctly and not my genkernel kernel or hand-made kernel???
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