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

[GivePeaceAChance]

Hi,

So last night after getting errors trying to install wireless-tools for my laptop during the Gentoo installation, I removed the -Wall -Werror flags I had in my CXXFLAGS and compiled everything like a charm. When I try to boot Gentoo, however, I get the following error:

VFS: Cannot open root device "sdb4" or unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

Now I've checked and double-checked my fdisk partition table and my grub boot menu, and cross-referenced it with the example partition scheme in the Handbook.

My fdisk table is the following:

/dev/sdb1 is swap space
/dev/sdb2 is ReiserFS running Ubuntu
/dev/sdb3 is /boot for Gentoo
/dev/sdb4 is / for Gentoo

My GRUB entry for Gentoo is:

title=Gentoo Linux 2.6.20-r8
root (hd1,2) [hd1,2 is sdb3 which is my Gentoo boot]
kernel /boot/kernel-2.6.20-gentoo-r8 root=/dev/sdb4 [sdb4 is my / partition]

The manual has the following partition scheme:

/dev/hda1 is boot
/dev/hda2 is swap
/dev/hda3 is /

The manual offers the following as an example for GRUB:

title=Gentoo Linux 2.6.19-r5
root (hd0,0)
kernel /boot/kernel-2.6.19-gentoo-r5 root=/dev/hda3

Therefore, root (hd0,0) for them is like root (hd1,2) for me
Therefore root=/dev/hda3 for them is like root=/dev/sdb4 for me

Just like I have already. And it still won't load. I'm out of ideas, and I'm hoping someone out there can help me out. I've had great help from a few people already on other topics, and this one was started in the wireless-tools thread of mine, but I figured I'd put it here since it's a different issue.

- GPAC

[devils casper]

how many Harddisks are plugged-in your machine?
why SATA disk is sdb? if you have only one SATA disk, it should be sda.
post the contents of Gentoo's /boot/grub/device.map file and output of fdisk -l command.

[GivePeaceAChance]

The sdb is because I have two hard disks. Toshiba Qosmio G30 for ya. windows on one disk, linux on the other. I'll post what you want in about an hour. Cheers.

[GivePeaceAChance]

Hmmm.... I'm looking here and I have no device.map in the directory you specified.

My Gentoo fstab:

/dev/sdb1               none            swap            sw               0 0
/dev/sdb2               /mnt/Ubuntu     reiserfs        user,notail      0 1
/dev/sdb3               /boot           ext2            user,noauto      1 2
/dev/sdb4               /               ext3            user,noatime     0 1

/dev/sda1               /media/Windows  ntfs    user,nls=utf8,umask=0222 0 0
/dev/sda2               /media/fat32    vfat    users,defaults,umask=000 0 0

/dev/cdrom              /mnt/cdrom      auto            auto,user        0 0

And here's the output fdisk -l gave me:

Disk /dev/sda: 95.0 GB, 95034885120 bytes
255 heads, 63 sectors/track, 11554 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        1306    10490413+   7  HPFS/NTFS
/dev/sda2            1307        1567     2096482+   c  W95 FAT32 (LBA)
/dev/sda3            1568       11553    80212545    7  HPFS/NTFS

Disk /dev/sdb: 100.0 GB, 100030242816 bytes
255 heads, 63 sectors/track, 12161 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1          65      522081   82  Linux swap / Solaris
/dev/sdb2              66         457     3148740   83  Linux
/dev/sdb3   *         458         462       40162+  83  Linux
/dev/sdb4             463       12161    93972217+  83  Linux

P.S. Damn, that command is handy. Nice tables!

[devils casper]

there must be a device.map file in /boot/grub folder. GRUB looks in device.map file for disk names.
according to output of 'fdisk -l' command and contents of /etc/fstab, contents of device.map file should be

(hd0)  /dev/sda
(hd1)  /dev/sdb

if there isn't any device.map file in Gentoo's /boot/grub, create new and type above code.

[GivePeaceAChance]

I checked Ubuntu's grub and the file was there, so I checked the contents via cat and copied the file to /gentoo/boot/grub. I reboot my computer and trying getting into Gentoo again, but nothing. I'm assuming what you told me to do wasn't the end of my woes. So what next?

[devils casper]

post the contents of Ubuntu's menu.lst file.

[GivePeaceAChance]

The following is Ubuntu's menu.lst, however it is not the current one grub is using.

title           Ubuntu, kernel 2.6.15-28-386
root            (hd1,1)
kernel          /boot/vmlinuz-2.6.15-28-386 root=/dev/sdb2 ro quiet splash
initrd          /boot/initrd.img-2.6.15-28-386
savedefault
boot

### END DEBIAN AUTOMAGIC KERNELS LIST

# This is a divider, added to separate the menu items below from the Debian
# ones.
title           Other operating systems:
root


# This entry automatically added by the Debian installer for a non-linux OS
# on /dev/sda1
title           Windows XP Media Center Edition
root            (hd0,0)
savedefault
makeactive
chainloader     +1

The current one grub is using in in gentoo's /boot/grub, which is this:

title=          Gentoo Linux
root            (hd1,2)
kernel          /boot/kernel-2.6.20-gentoo-r8 root=/dev/sdb4

title=          Ubuntu Linux
root            (hd1,1)
kernel          /boot/vmlinuz-2.6.15-28-386 root=/dev/sdb2 ro quiet splash
initrd          /boot/initrd.img-2.6.15-28-386
boot

title=          Windows XP Media Center Edition
root            (hd0,0)
makeactive
chainloader +1

[Steve0008]

A few quick questions to try and narrow down the problem...
-Do Windows and Ubuntu boot using this grub.conf?
-Has Gentoo ever booted before from this grub.conf?

I ask these because this looks to me like more of a kernel problem than a grub problem. The grub.conf looks correct to me assuming you placed the bzImage in the correct place. Sorry if I'm restating anything anyone else said or something you've answered before, but skimming through the posts, I didn't see anything mentioned about your kernel.

[devils casper]

I ask these because this looks to me like more of a kernel problem than a grub problem. The grub.conf looks correct to me assuming you placed the bzImage in the correct place. Sorry if I'm restating anything anyone else said or something you've answered before, but skimming through the posts, I didn't see anything mentioned about your kernel

I Agree. something is wrong with kernel only. grub.conf file is configured correctly. problem is coz of kernel only.