[SOLVED] rootdevice "fc03" or unknown-block(252,3): error -6

Message

guid0 · Post by **guid0** » Sat Mar 09, 2013 9:29 pm

-blam i cannot even boot the machine-

FULL ERRORMESSAGE:

VFS: Cannot open rootdevice "fc03" or unknown-block(252,3): error -6

Im trying to restore a bare-metal gentoo setup into a kvm-vm (one of many) in a sort of stage4 way. I have full OS in tarbal and a gentoo bootcdrom.

I have set the usual kernelfeatures:

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CONFIG_VIRT_TO_BUS=y
CONFIG_VIRTIO_BLK=y
CONFIG_VIRTIO_NET=y
CONFIG_VIRTIO_CONSOLE=y

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CONFIG_BLK_DEV_BSG=y
CONFIG_BLK_DEV=y
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y

adjusted some files

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/etc/fstab

even regenerated

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/etc/mtab

en tried lilo several times in a repeating process.

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livecd ~ # chroot /mnt/gentoo/

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cat /etc/lilo.conf

lba32
boot=/dev/vda
disk=/dev/vda bios=0x80 max-partitions=7
map = /boot/.map
install = /boot/boot-menu.b
menu-scheme=Wb
prompt
timeout=80
delay = 50
image = /boot/vmlinuz-3.8.1
root = /dev/vda3
label = 3.8.1
read-only

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livecd / # lilo

Warning: /proc/partitions references Experimental major device 252.
Warning: /proc/partitions references Experimental major device 252.
Warning: /proc/partitions references Experimental major device 252.
Warning: /proc/partitions references Experimental major device 252.
Added 3.8.1 *
4 warnings were issued.

However,.. on umount and reboot from virtual disk i get at around 5seconds of kernel-time:

VFS: Cannot open rootdevice "fc03" or unknown-block(252,3): error -6

Now here is what is weird. The Gentoo install-amd64-minimal-20130110.iso CD boots the environment with the following devices:
[*]LIVECD

livecd / # ls -laF /dev/vda*
brw-rw---- 1 root disk 252, 0 Mar 9 22:07 /dev/vda
brw-rw---- 1 root disk 252, 1 Mar 9 15:44 /dev/vda1
brw-rw---- 1 root disk 252, 2 Mar 9 15:44 /dev/vda2
brw-rw---- 1 root disk 252, 3 Mar 9 15:44 /dev/vda3
etc

[*]OTHER VIRT MACHINE

machine / # ls -laF /dev/vda*
brw-rw---- 1 root disk 254, 0 Mar 9 22:07 /dev/vda
brw-rw---- 1 root disk 254, 1 Mar 9 15:44 /dev/vda1
brw-rw---- 1 root disk 254, 2 Mar 9 15:44 /dev/vda2
brw-rw---- 1 root disk 254, 3 Mar 9 15:44 /dev/vda3
etc

So this currently leaves me with either unsupported vanilla-kernel installcd combination or mknod adjustable things to try.. unless this is a BUG EATING MY SHOE

Anyways, I would like to end debugging this process more quickly and kindly ask for any hint whatsoever whilst i try my last options.

Cheers,
guid0

guid0 · Post by **guid0** » Sat Mar 09, 2013 9:37 pm

indeed,.. as i already figured.. below does not help.

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livecd ~ # rm /dev/vda2 
rm: remove block special file '/dev/vda2'? y
livecd ~ # rm /dev/vda4
rm: cannot remove '/dev/vda4': No such file or directory
livecd ~ # rm /dev/vda3
rm: remove block special file '/dev/vda3'? y    
livecd ~ # rm /dev/vda 
rm: remove block special file '/dev/vda'? y
livecd ~ # mknod -m 660 /dev/vda3 b 254 3
livecd ~ # mknod -m 660 /dev/vda2 b 254 2
livecd ~ # mknod -m 660 /dev/vda1 b 254 1
livecd ~ # mknod -m 660 /dev/vda b 254 0
livecd ~ # chown root:disk /dev/vda*
livecd ~ # mount /dev/vda3 /mnt/gentoo/
mount: /dev/vda3 is not a valid block device

too tired to tinker with other kernels..

Ant P. · Post by **Ant P.** » Sat Mar 09, 2013 10:26 pm

Last time I tried, the only thing that booted reliably with a virtio disk was grub2.

guid0 · Post by **guid0** » Sat Mar 09, 2013 10:27 pm

Ant P. wrote:Last time I tried, the only thing that booted reliably with a virtio disk was grub2.

thing is, i have shedloads of virtual machines running lilo with that exact same config file. using grub/grub2 for this one pushes system administration in an awkward direction. id like to hold that off for a bit..

Post by **NeddySeagoon** » Sat Mar 09, 2013 10:59 pm

guid0,

I use grub1 on my KVMs. I run LVM on the underlying hardware and they all get a logical volume for disk space, which is further partitioned inside the KVM.

At face value

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unknown-block(252,3)

says the volume was found but the filesystem there cannot be read.
Given that you have stage4ed the VM, thats exceedingly unlikely

guid0 · Post by **guid0** » Sun Mar 10, 2013 7:45 am

Thanks again for your response NeddySeagoon your almost 30k posts are impressive.

I wonder if this procedure is borked because the original system from which the stage4 is snapped is running a software raid1 setup.
Cant really imagine why though...

guid0

guid0 · Post by **guid0** » Sun Mar 10, 2013 8:09 am

Here we go..

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[ebuild  N     ] sys-boot/grub-0.97-r12  USE="-custom-cflags -ncurses -netboot -static" 1,034 kB

/boot/grub/grub.conf:

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default 0
timeout 30
splashimage=(hd0,0)/boot/grub/splash.xpm.gz

title Gentoo Linux 3.8.1
root (hd0,0)
kernel /boot/vmlinuz-3.8.1 root=/dev/vda3

but another fail..

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Probing devices to guess BIOS drives. This may take a long time.

    GNU GRUB  version 0.97  (640K lower / 9216K upper memory)

 [ Minimal BASH-like line editing is supported.  For the first word, TAB
   lists possible command completions.  Anywhere else TAB lists the possible
   completions of a device/filename. ]
grub> root (hd0,0)
root (hd0,0)

Error 21: Selected disk does not exist

guid0 · Post by **guid0** » Sun Mar 10, 2013 8:41 am

same issue using an ubuntu-server install iso. im kinda lost here..

guid0 · Post by **guid0** » Sun Mar 10, 2013 9:10 am

Fixed using

grub> device (hd0) /dev/vda
device (hd0) /dev/vda
grub> root (hd0,0)
root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
grub> setup (hd0)
setup (hd0)
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/e2fs_stage1_5" exists... yes
Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 22 sectors are embedded.
succeeded
Running "install /boot/grub/stage1 (hd0) (hd0)1+22 p (hd0,0)/boot/grub/stage2 /boot/grub/menu.lst"... succeeded
Done.

At least the system boots now.. will solve as soon as lilo works again

guid0 · Post by **guid0** » Sun Mar 10, 2013 11:09 am

fixed using grub to boot and managed to switch back to lilo using below command

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machine734 ~ # lilo
Warning: /proc/partitions references Experimental major device 254.
Warning: /proc/partitions references Experimental major device 254.
Warning: /proc/partitions references Experimental major device 254.
Warning: /proc/partitions references Experimental major device 254.
Added 3.8.1 *
4 warnings were issued.

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reboot

yay!
guid0

Post by **NeddySeagoon** » Sun Mar 10, 2013 4:08 pm

guid0,

OK, ... but why?

guid0 · Post by **guid0** » Sun Mar 10, 2013 4:58 pm

guid0 wrote:thing is, i have shedloads of virtual machines running lilo with that exact same config file. using grub/grub2 for this one pushes system administration in an awkward direction. id like to hold that off for a bit..

fixing 1 system with lilo literally saves me weeks of work and reboots to ensure grub/grub2 works as expected.

Post by **NeddySeagoon** » Sun Mar 10, 2013 5:45 pm

guid0,

I intended you to speculate on why installing grub allowed lilo to work?
It smacks of clock skew but I can't really explain it.

guid0 · Post by **guid0** » Sun Mar 10, 2013 7:38 pm

I can only guess at it. It surely wasnt a clock skew. I have been bitten by the clock several times before and its something I checked.

I tried stracing lilo but that wasnt really helpful either. The only thing I can currently think of is that the original setup was created many many years ago (somewhere 2005). I went through several update cycles and may have run a 2.4 kernel if not an early 2.6 tree before moving into 3.x which was done only recently.

Perhaps lilo left some map files around that were somewhat stoneaged. I really dont know. Grub didnt do it either until i provided the device (hd0) /dev/vda line. Manually updating the devices.map in grub turned out to be useless.

guid0

Post by **NeddySeagoon** » Sun Mar 10, 2013 7:49 pm

guid0,

I installed my KVMs using emulated hardware, so grub did not have issues like that and switched to virtio hardware later.
In fact, I only ever installed one very basic KVM and cloned it everywhere, then added to the clones.