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manu_leo
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PostPosted: Fri Jan 16, 2015 8:23 pm    Post subject: Kernel Panic error when starting server. Reply with quote

Hi Experts, I am trying to do a fresh install on my server and after the installation when I restart the server, it gives me a Kernel Panic error.

Kernel Panic - not syncing : VFS: unable to mount root fs on unknown block (8,1)

I have 4 partitions configured as below :-
Quote:
/dev/sda1
/dev/sda2
/dev/sda3
/dev/sda4


Quote:
/dev/sda1
is my boot partition and I think (8,1) implies sda1 .

I checked the /boot/grub/grub.cfg file and I see there
Quote:
root=/dev/sda1 ro single


Raid 0 is configured with all the 4 hdd in it.

Please suggest if I am missing something here.

Appreciate all your help in advance. Thanks a ton.
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NeddySeagoon
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PostPosted: Fri Jan 16, 2015 8:30 pm    Post subject: Reply with quote

manu_leo,

unknown block (8,1) does indeed mean /dev/sda1
If thats your boot partition, it won't be your root.

unknown block (8,1) tells that the kernel can see /dev/sda1 but not read the contents, usually due the the required filesystem driver not being available.

However, you mentioned raid0. Tell how the raid set is configured and assembled and tell us where / (root) is
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manu_leo
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PostPosted: Fri Jan 16, 2015 8:38 pm    Post subject: Reply with quote

Thanks Neddy.

/dev/sda1 is mounted to / AND also it is configured as boot.

I configured RAID 0 by entering the RAID utility, and then bundling the 4 drives into 1 VD and initializing them. There are 4*135GB HDD.

Please let me know if I missed something here.
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NeddySeagoon
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PostPosted: Fri Jan 16, 2015 9:00 pm    Post subject: Reply with quote

manu_leo,

Is root inside the raid0 set?

You say you you entered the RAID utility, and then bundling the 4 drives into 1 VD.
That implies that you are using fake raid over four entire drives. If thats correct, root is inside the raid0 set, you need support for your fake raid before root can be mounted.

The alternative is that /dev/sda is a hardware raid set and all of its companents and its raid structure are invisible to the operating system.
In this case /dev/sda1 would be correct and you need support for your hardware raid card, which seems to be present.

Tell us more about your setup and partitioning scheme.
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manu_leo
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PostPosted: Sat Jan 17, 2015 10:35 am    Post subject: Reply with quote

Setup is a simple one. Raid-0 configured with 4 drives.

/dev/sda1 mounted on /
/dev/sda2 is the swap
/dev/sda3 mounted on /var
/dev/sda4 mounted on /home

fstab entries made accordingly. This same setup works fine on all the other servers I have. I think I am missing something in the kernel built.

Appreciate all your help.
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NeddySeagoon
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PostPosted: Sat Jan 17, 2015 11:24 am    Post subject: Reply with quote

manu_leo,

Explain about your raid setup.

Raid partitions in Linux are /dev/mapper/... for fakeraid
/dev/md... for mdadm raid.

They may be /dev/sd... for hardware raid.

It matters as with fakeraid and mdadm raid, its still possible to access the underlying /dev/sd... devices.
That's a very bad thing to do but its still possible.

At face value, with hardware raid and the error unknown block (8,1), the root filesysem driver is missing from your kernel.
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manu_leo
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PostPosted: Sat Jan 17, 2015 12:01 pm    Post subject: Reply with quote

That could be very well the case that the root file system drivers may not be there. Could you please help me as to how to enable the root filesysem driver in Kernel.

Thanks for all the help.
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NeddySeagoon
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PostPosted: Sat Jan 17, 2015 12:32 pm    Post subject: Reply with quote

manu_leo,

What filsystem do you have on your root?
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manu_leo
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PostPosted: Sat Jan 17, 2015 1:12 pm    Post subject: Reply with quote

It is ext4.

I formatted all the 3 drives - sda1, sda3, sda4 with ext4 . sda2 is the swap.
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NeddySeagoon
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PostPosted: Sat Jan 17, 2015 1:18 pm    Post subject: Reply with quote

manu_leo,

What does
Code:
grep EXT4 /usr/src/linux/.config
show?

I get
Code:
CONFIG_EXT4_FS=y
CONFIG_EXT4_USE_FOR_EXT23=y
# CONFIG_EXT4_FS_POSIX_ACL is not set
# CONFIG_EXT4_FS_SECURITY is not set
# CONFIG_EXT4_DEBUG is not set

If you have CONFIG_EXT4_FS=m you will need an initrd to boot as you need the ext4 module to mount root.
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manu_leo
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PostPosted: Sat Jan 17, 2015 2:06 pm    Post subject: Reply with quote

Yes I have these 2 option set as Y and not as a module.

Quote:
CONFIG_EXT4_FS=y
CONFIG_EXT4_USE_FOR_EXT23=y
# CONFIG_EXT4_FS_POSIX_ACL is not set
# CONFIG_EXT4_FS_SECURITY is not set
# CONFIG_EXT4_DEBUG is not set
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NeddySeagoon
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PostPosted: Sat Jan 17, 2015 2:48 pm    Post subject: Reply with quote

manu_leo,

Its not that then.
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NeddySeagoon

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