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Linux : unable to boot : Kernel panic

Posted on 2012-12-26
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Last Modified: 2013-01-07
Hello,

After restarting my server, i receive a "Kernel panic : not syncing vfs unable to mount root fs on unknown-block"
The distro is : ubuntu-server 10.1 and i have a rescue disk where i have try in chroot to :

apt-get purge linux-image
update-grub

to fix the boot sequence like some guides founded on web but nothing change and i stay with my kerne-panic

Appreciate any  help

Thanks in advance
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Comment
Question by:SA-IT
14 Comments
 
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Expert Comment

by:odintsov
ID: 38720985
Hello,

Could you show full kernel boot log (not only error about vfs)?
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Expert Comment

by:Darr247
ID: 38721180
I believe when you do
apt-get purge linux-image
you need to specify the latest kernel or it doesn't know which one to uninstall.
You should find those in the /boot/ subdirectory.
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Author Comment

by:SA-IT
ID: 38721206
Hi Odintsov,

I found nothing on /var/log except outdated logfiles.
My kernel does'nt boot at all and the exact message is : "kernel panic 1.645097 : not syncing vfs unable to mount root fs on unknown-block"

My Linux system is installed on virtual machine but there is nothing changed on my environment.

I think system is trying to boot on a kernel who isn't install
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Author Comment

by:SA-IT
ID: 38721213
Hi Darr247,
I have specified the kernel and with the "uname -a" commande i have see that the downgrade process successfuly .
I have made a "update-grub" and "upgrade-grub2" but i'm not sure grub is used on my server.

thanks for all
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Author Comment

by:SA-IT
ID: 38721310
I have found way to display grub menu ( hold shift key ) and in rescue mode i have somes informations maybe usefull

(Look at the capture)

Thanks for all
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Author Comment

by:SA-IT
ID: 38721365
i have found that my /boot partition was full.

there is probably the reason cause the issue?
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Expert Comment

by:Darr247
ID: 38721717
How many kernels are installed?

What version of grub do you have, exactly?
Run
grub-install -v
to find out.
In 1.99 and newer, it only shows you the latest kernel in its menu, and you have to choose the Previous Linux versions
entry to display a list of the older kernels (on the initial menu it should also offer a chance to run memtest86). If you have 8 or 10 older kernels, you might want to pare those down to 3 or 4 to make more free space on your /boot partition... uninstalling/purging the oldest images first. I would reboot between removing each one, so if something goes wrong, you'll know at exactly what point it messed up. It's a good idea to keep at least 2 backup kernels in case you discover incompatibilites in the newest kernel[s].
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Author Comment

by:SA-IT
ID: 38723351
Hi Darry,

There was a lot of kernel installed but i have cleaned yesterday with "apt-get remove linux-server-2.6.32-3*" to remove all version except last relase 2.6.32-45.
My grub version is 0.97

I have successfully power on my machine on very old kernel yesterday but with no eth  interface. Now
this is a list of files on /boot
 list on /boot
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Author Comment

by:SA-IT
ID: 38723368
It's really strang because when i hold shift key on boot i get a grub menu where the version is différent

grub2?
Thanks all for ur help
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Expert Comment

by:Darr247
ID: 38723888
You may have 0.97 installed, but grub 1.98 (as shown in the screen cap above) is being used.

0.97 is "legacy grub"; 1.98 and later is called grub2 (1.97 was grub2 beta).

You should refer to https://help.ubuntu.com/community/Grub2
for complete instructions to understand your version of grub... you can't just edit menu.lst like with legacy grub (grub2 does not use menu.lst at all... if it's present, that's because you have 0.97 installed, too).
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Expert Comment

by:gheist
ID: 38734308
purge deletes everything ignoring dependencies. Congratulations with uninstalling kernel. Sort of there is a copy con kernel on install CD/DVD which you can install using upgrade procedure.

Effect will be similar removing upstart/initscripts and/or libc or lvm2.... Just some packages are needed to boot the system..
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Author Comment

by:SA-IT
ID: 38750141
I have simply reinstall my server from scratch.
Thanks all for all proposition.
Best regards
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Accepted Solution

by:
Darr247 earned 500 total points
ID: 38750537
In http:#a38721717 I said:
I would reboot between removing each one, so if something
goes wrong, you'll know at exactly what point it messed up.
It's a good idea to keep at least 2 backup kernels in case you
discover incompatibilites in the newest kernel[s].

Do keep that in mind in the future when removing old kernels.
0
 

Author Comment

by:SA-IT
ID: 38750647
thanks for advices
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