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#1 2011-02-10 20:44:37

aramis_qc
Member
From: Québec - Canada
Registered: 2010-10-07
Posts: 312

[SOLVED] VFS cannot open root device - unknown block

I really don't understand why. All my other installations start but the last one. Others run 2.6.36-r5 kernel. The latest is testing so it is kernel 2.6.37-r1. There is a device.map in /boot/grub and devices are well identified.

device.map

cat /boot/grub/device.map
(hd0)    /dev/sda
(hd1)    /dev/sdb

output of fdisk -l

fdisk -l

Disque /dev/sda: 500.1 Go, 500107862016 octets
255 têtes, 63 secteurs/piste, 60801 cylindres
Unités = cylindres de 16065 * 512 = 8225280 octets
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Identifiant de disque : 0x0001a426

Périphérique Amorce  Début        Fin      Blocs     Id  Système
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14        1058     8393962+  82  Linux swap / Solaris
/dev/sda3            1059        7586    52436160   83  Linux
/dev/sda4            7587       60801   427449487+  83  Linux

Disque /dev/sdb: 500.1 Go, 500107862016 octets
255 têtes, 63 secteurs/piste, 60801 cylindres
Unités = cylindres de 16065 * 512 = 8225280 octets
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Identifiant de disque : 0xcb902696

Périphérique Amorce  Début        Fin      Blocs     Id  Système
/dev/sdb1               1        6079    48829536   83  Linux
/dev/sdb2            6092       60801   439458075    5  Etendue
/dev/sdb5            6092       12316    50002281   83  Linux
/dev/sdb6           12317       13561    10000431   83  Linux

fstab of latest installation

# /etc/fstab: static file system information.
#
# The root filesystem should have a pass number of either 0 or 1.
# All other filesystems should have a pass number of 0 or greater than 1.
#
# NOTE: If your BOOT partition is ReiserFS, add the notail option to opts.
#
# See the manpage fstab(5) for more information.
#
# <fs>                  <mountpoint>    <type>          <opts>                   <dump/pass>

/dev/sda1               /boot           ext2            noauto,noatime           1 2
/dev/sda2               none            swap            sw                       0 0
/dev/sdb5               /               ext4            noatime                  0 1
/dev/sdb6               /home           ext4            defaults,noatime         0 1
#/dev/cdrom             /mnt/cdrom      auto            noauto,ro                0 0
none                    /dev/shm        tmpfs           nodev,nosuid,noexec      0 0

Need anything else to help me with fixing that ?

Last edited by aramis_qc (2011-02-11 02:58:28)

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#2 2011-02-10 23:54:02

rh1
_Member
From: Eastern Shore, VA
Registered: 2010-10-08
Posts: 388

Re: [SOLVED] VFS cannot open root device - unknown block

Off the top of my head, first guess would be that you have incorrect root partition specified in grub.cfg, second guess would be that you didn't include ext4 support in the kernel.

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#3 2011-02-11 00:33:49

aramis_qc
Member
From: Québec - Canada
Registered: 2010-10-07
Posts: 312

Re: [SOLVED] VFS cannot open root device - unknown block

Here is /boot/grub/grub.cfg :

set timeout=5

menuentry "Funtoo GNU/Linux - vmlinuz-2.6.36-gentoo-r5" {
  insmod part_msdos
  insmod ext2
  set root=(hd0,1)
  search --no-floppy --fs-uuid --set 3f6c3f87-1d45-45b9-8f38-400a5ed683ed
  linux /vmlinuz-2.6.36-gentoo-r5 rootfstype=ext4 root=/dev/sda3
  set gfxpayload=keep
}

menuentry "Funtoo GNU/Linux - testing - bzImage-2.6.37-gentoo" {
  insmod part_msdos
  insmod ext2
  set root=(hd0,1)
  search --no-floppy --fs-uuid --set 3f6c3f87-1d45-45b9-8f38-400a5ed683ed
  linux /bzImage-2.6.37-gentoo rootfstype=ext4  root=/dev/sdb5
  set gfxpayload=keep
}
set default=0

As you can see, /root is on /dev/sdb5.

ext4 is included in kernel.

http://www.funtoo-quebec.org/wiki/index … ystems.png

Full .config : http://paste.pocoo.org/show/336176/

Filesystems is configured the same way on my desktop to the exception that kernel is 2.6.36-r5. It is also a dual boot but with Debian GNU/Linux and it is grub-legacy instead of grub2.

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#4 2011-02-11 00:42:06

rh1
_Member
From: Eastern Shore, VA
Registered: 2010-10-08
Posts: 388

Re: [SOLVED] VFS cannot open root device - unknown block

Not sure what it could be then. Everything looks correct. Could you post the entire error message?

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#5 2011-02-11 00:46:35

aramis_qc
Member
From: Québec - Canada
Registered: 2010-10-07
Posts: 312

Re: [SOLVED] VFS cannot open root device - unknown block

Gotta restart and write down whole message. Everything freezes and I can't use console. Back in a few minutes.

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#6 2011-02-11 00:55:23

aramis_qc
Member
From: Québec - Canada
Registered: 2010-10-07
Posts: 312

Re: [SOLVED] VFS cannot open root device - unknown block

The whole thing :

VFS : Cannot open root device "sdb5" or unknown-block(0,0)

Please append a correct "root=" boot option; here are the available partitions :  (rest of line blank)

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

Follow contents of Call Trace and a message telling panic occured switching back to text console

Last edited by aramis_qc (2011-02-11 00:56:07)

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#7 2011-02-11 01:03:55

404_Error
Core Team Member
From: Quebec city, Quebec, Canada
Registered: 2010-10-08
Posts: 511

Re: [SOLVED] VFS cannot open root device - unknown block

1. Remove rootfstype=, this is useless as  the kernel autodetects what your filesystem type is
2. Comment out your "search" lines and see if you have the same issues

If the kernel still panics, it may be related to a tricky option that has not been activated in the kernel but used in the filesystem.  Also, may sound stupid, but are you sure you have the right kernel image at the right place?  Another option could be that, for some reasons, the ext4 filesystem on /dev/sdb5 is corrupted (e2fsck /dev/sdb5 is recommended).

First guesses however.

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#8 2011-02-11 01:11:47

aramis_qc
Member
From: Québec - Canada
Registered: 2010-10-07
Posts: 312

Re: [SOLVED] VFS cannot open root device - unknown block

I did remove rootfstype before I posted here and same happended.

What are search lines you talk about ?

kernel image is store in /boot on sda1. It was on sdb5 but I'm told that you must use only one /boot with GRUB2. So I moved kernel to sda1 and deleted sdb5 (it was /boot at that time). Now sdb5 is / and I ameded fstab accordingly.

I'm running a test on sdb.

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#9 2011-02-11 01:12:57

rh1
_Member
From: Eastern Shore, VA
Registered: 2010-10-08
Posts: 388

Re: [SOLVED] VFS cannot open root device - unknown block

I found this while searching around

this error message means that the kernel doesn't know what device you mean for your root device and thus / cannot be mounted. the block device number (0,0) means that the device specified is completely unknown to the kernel (as opposed to cases where there is (3,1) or similar, then it would mean that the kernel doesn't understand the filesystem on the device).

Maybe you didn't enable the right drivers for your harddrive? I don't have alot of knowledge about it though so i can't really help you with that.

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#10 2011-02-11 01:21:34

whiteghost
Member
From: north dakota
Registered: 2010-10-10
Posts: 155

Re: [SOLVED] VFS cannot open root device - unknown block

i've made many kernels but often make same mistake. not enabling chipset driver.

a great help is linux sea. chapter 7 is about kernels and trouleshooting

http://swift.siphos.be/linux_sea/

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#11 2011-02-11 01:22:27

404_Error
Core Team Member
From: Quebec city, Quebec, Canada
Registered: 2010-10-08
Posts: 511

Re: [SOLVED] VFS cannot open root device - unknown block

Those in /boot/grub/grub.cfg.

Else my feeling rejoins the same one expressed above : your controller/harddrive is not seen by the kernel or something like "SCSI disk support" is missing (IDE/SATA drives are seen as SCSI drives if you use libATA in your kernel). What is true for IDE/SATA hard drives is also true for optical drives btw.

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#12 2011-02-11 02:58:04

aramis_qc
Member
From: Québec - Canada
Registered: 2010-10-07
Posts: 312

Re: [SOLVED] VFS cannot open root device - unknown block

whiteghost wrote:

i've made many kernels but often make same mistake. not enabling chipset driver.

a great help is linux sea. chapter 7 is about kernels and trouleshooting

http://swift.siphos.be/linux_sea/

Thank's a lot... It really helped me... I missed AHCI when I ran lspci... Now it is set (<*> AHCI SATA support) and kernel recompiled... It works now.

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