How to change root_dev for 2.6.27.7 kernel?

galapogos · 12-04-2008, 12:09 AM

Hi,

I'm trying to update the kernel in 1 of my drives from 2.6.22.19 to
the latest stable 2.6.27.7 release. It seems that some changes
happened.

First, arch/i386/boot has been replaced by arch/x86/boot. Also the
boot sector file bootsect no longer exists, and the build command's
syntax has changed to reflect this.

I have previously been able to build an uncompressed kernel whose
rootdev is /dev/sda1 with the following script:

Code:

echo "Builds uncompressed Image here with root device as /dev/sda1"
mknod  /dev/sda1 b 8 1
objcopy -O binary -R .note -R .comment -S vmlinux tmppiggy
cd arch/i386/boot
tools/build -b bootsect setup ../../../tmppiggy /dev/sda1 > ../../../Image_sda
cd -
echo "The uncompressed image can only boot from /dev/sda1 and is
called Image_sda"

However, I'm unable to do this even after changing the directory
names, because the file "setup" doesn't exist.

I have tried manually modifying ROOT_DEV in arch/x86/boot/Makefile
from CURRENT to "/dev/sda1" and the when I do a "file bzImage" it
gives the following output:

Code:

bzImage: Linux kernel x86 boot executable RO-rootFS, root_dev 0x801,
swap_dev 0x1, Normal VGA

My old kernel 2.6.22.19, after running the script, has a swap_dev of
0x2 instead.

I'm not sure what else is different, however I'm having trouble
booting up with the new image in some(not all) systems. It boots up
until the following stage then kernel panics:

Code:

FS: Cannot open root device "801" or unknown-block (8,1)
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(8,1)

Any ideas how I can get build to change my root_dev/swap_dev? I've
tried using the setup.elf, as well as copying setp from the 2.6.22.19
kernel and running the command without the "bootsect" parameter, but
it gives me the message:

Code:

Boot block hasn't got boot flag (0xAA55)

Thanks.

bapigoo9 · 12-04-2008, 08:41 PM

Quote:

I'm not sure what else is different, however I'm having trouble
booting up with the new image in some(not all) systems. It boots up
until the following stage then kernel panics:

Can you explain what you mean that it boots up on some systems, but not on some other systems? How are you booting? What bootloader are you using, and how are you using the kernel on different systems?

galapogos · 12-04-2008, 11:51 PM

Sorry. I'm using LILO as my boot loader. The Linux kernel is a very stripped down version and all it does it boots up into a busybox shell. I'm using the kernel the same way on different systems. The idea is to have 1 kernel that works for as many systems as possible - i.e. as long as the drive is connected as /dev/sda it should work. I believe the problem with my new kernel is that I'm not changing root_dev/swap_dev properly as I was with the old kernel. So I'm just wondering how I can do that with the "build" command with the new kernel.

bapigoo9 · 12-07-2008, 01:26 AM

Quote:

all it does it boots up into a busybox shell

So, it boots up to a busybox shell on several different computers as long as the harddrive is in /dev/sda? It does not boot up into Linux? To make some things easier, what distro are you mostly using with this kernel?

Quote:

I'm using the kernel the same way on different systems. The idea is to have 1 kernel that works for as many systems as possible

That is what the "generic" Linux kernels from major distros are for.

With the newer kernels, you need an initrd to boot up into Linux on the machine. If you update your distro, it usually includes the initrd too.

galapogos · 12-07-2008, 02:44 AM

Quote:

Originally Posted by bapigoo9

So, it boots up to a busybox shell on several different computers as long as the harddrive is in /dev/sda? It does not boot up into Linux? To make some things easier, what distro are you mostly using with this kernel?

Yes. That's the basic idea/goal. I'm not using any distro at all. It's completely built from the ground up.

Quote:

That is what the "generic" Linux kernels from major distros are for.

With the newer kernels, you need an initrd to boot up into Linux on the machine. If you update your distro, it usually includes the initrd too.

Well, my kernel does not have initrd. It boots up in several PCs, just not some. Can we get back to the original question about the build command? I believe that's the problem.

galapogos · 12-16-2008, 01:53 AM

Can anyone help?

bapigoo9 · 01-11-2009, 06:10 PM

Quote:

Originally Posted by galapogos

Can anyone help?

We can help if you clarify your questions! What exactly are you trying to do? Build the new kernel?

galapogos · 01-11-2009, 08:32 PM

OK, I'll try my best to clarify.

I have built the kernel already, and gotten the kernel image. However, the kernel image is default build against my Mandriva Linux installation, which is installed in /dev/sda6 or something. However, this is not what I want, because I'm not building the new image to upgrade my Mandriva Linux, but rather to install it on another Linux installation on another device, which boots up from /dev/sda1 instead. However, this other Linux installation is extremely minimal(it's sort of an embedded device) so it doesn't have gcc and all the other necessary tools for kernel compilation, hence my development PC is another Mandriva Linux box.

With previous kernel versions 2.6.22.19 and earlier, I was able to use the "build" command to change the kernel's root_dev to /dev/sda1, and this boots up just fine.

With the newer kernel versions(I've tried 2.6.27.7), the "build" command syntax has changed and I'm haven't figured out how to use it. However, I've still managed to change the root_dev by manually modifying ROOT_DEV in arch/x86/boot/Makefile
from CURRENT to "/dev/sda1", and I've verified that this does, indeed, change the root_dev of the kernel image.

However, despite doing this, I am still getting kernel panics when booting up from some(not all) PCs, with the following panic message:

Code:

FS: Cannot open root device "801" or unknown-block (8,1)
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(8,1)

I'm not sure why this is the case because (8,1) is /dev/sda1 as far as I know

I'm using LILO and my lilo.conf has also been set to boot up from /dev/sda1, so I'm not sure what else I'm missing? My old 2.6.22.19 did not have these kernel panics with these PCs.

I hope that's clear enough?

Thanks!