# Booting new Kernel

## zirtik

Hi,

I installed Gentoo using the genkernel utility and compiled a fat kernel that includes everything that the live cd contains. So far, I have no problems running Gentoo with this kernel and everything works just fine.

Yesterday, I compiled a light kernel based on my needs to increase the performance of my system and modified grub.conf as follows:

```

default 0

timeout 10

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

title Gentoo 2.6.24-r5

root (hd0,0)

kernel /boot/kernel-genkernel-x86-2.6.36-gentoo-r8 root=/dev/ram0 init=/linuxrc ramdisk=8192 real_root=/dev/sda3

initrd /boot/initramfs-genkernel-x86-2.6.36-gentoo-r8

title Light Kernel

root (hd0,0)

kernel /boot/kernel-2.6.34-light2 root=/dev/sda3

```

as instructed in the Gentoo installation handbook. When I try to boot the system with the light kernel, I get a kernel panic error:

Root-NFS: no NFS server address

VFS: Unable to mount root fs via NFS, trying floppy.

VFS: Cannot open root device "sda3" or unknown-block (2,0)

Please append a correct "root=" boot option; here are the available partitions:

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)

Pid: 1, comm: swapper Not tainted 2.6.37-gentoo-r4 #2

I'm quite puzzled because I have nothing to do with NFS although I included NFS modules in the custom kernel to make sure it is not the issue.

What am I missing here? Is this a grub configuration problem or am I missing a module that must be in the kernel?

Thanks in advance.

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## Jon Wilder

Boot from the CD, mount your root and boot partitions to /mnt/gentoo and /mnt/gentoo/boot respectively, then try changing "root=/dev/sda3" to "root=/dev/hdg3" in /boot/grub/grub.conf. Also, change all of the "sda" entries in /etc/fstab to "hdg" as well.Try that configuration and see what happens when you try to boot to the kernel after making these changes. If that works you'll need to take a look at which SCSI/SATA drivers you compiled into your kernel.

If you're not chroot'ed you'll have to append the /mnt/gentoo to the beginning of those two file paths.

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## The Doctor

I seriously doubt that changing to sda to hdg will do anything other than make thinks worse. It looks like you missed the driver for you hard drive. Check out http://kernel-seeds.bloodnoc.org/ for instructions on how to find it.

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## cach0rr0

 *penguin swordmaster wrote:*   

> I seriously doubt that changing to sda to hdg will do anything other than make thinks worse. It looks like you missed the driver for you hard drive. Check out http://kernel-seeds.bloodnoc.org/ for instructions on how to find it.

 

agreed

in fact, newer udev will not even create /dev/hd* device nodes. So this step is pointless (with older udev, it would have been useful at least as a troubleshooting step, but the fear there is that users say 'hey, that works', and never change it until things break down the road)

OP: see the links in my signature, make sure the driver for your hard disk controller is a built-in (e.g. *not* a module, so it should =y and not =m), make sure you've done the file system you use for root as a built-in, not a module. Also, when you're in menuconfig, hit the /forward slash to search, and type in 'CONFIG_IDE'. If you have this enabled, things will break. It should not be enabled at all, even if you use an IDE hard drive. All of the new, correct IDE drivers, are now labeled as PATA drivers, and can be found beneath CONFIG_ATA (if you search for this, it SHOULD be enabled, and this is the only entry from which you should select any HDD drivers)

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## Hu

 *zirtik wrote:*   

> I'm quite puzzled because I have nothing to do with NFS although I included NFS modules in the custom kernel to make sure it is not the issue.

 If you have support for root on NFS and the kernel is unable to mount root from the hard drive, then it will try various other ways to get a root filesystem.  In this case, the failure to mount an NFS root is expected, since that is not how you intend to provide a root filesystem.

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## zirtik

Thank you all for the replies. I figured I was missing the SATA drives for my hard drive.  I included them in the kernel and successfully booted gentoo with my new kernel.

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