# Kernel Panic error when starting server.

## manu_leo

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
> ...

 

 *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

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

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

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

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

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

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

manu_leo,

What filsystem do you have on your root?

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## manu_leo

It is ext4.

I formatted all the 3 drives - sda1, sda3, sda4 with ext4 . sda2 is the swap.

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## NeddySeagoon

manu_leo,

What does

```
grep EXT4 /usr/src/linux/.config
```

show?

I get 

```
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

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
> ...

 

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## NeddySeagoon

manu_leo,

Its not that then.

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