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Requiremenets for a minimal Linux system

Hi. As a learning exercise I'm trying to piece together a very minimal Linux system. At the moment I keep getting a kernel panic suggesting that it can't load the root file system. I've been trying various different suggestions on which drivers I need and no joy.

It's occurred to me that some of the supporting system may be to blame and I was hoping someone might run their eyes over the following and let me know if there is anything missing or wrong with it:
(I know I will need to add more to make a useful system, I'm just after one that boots for now)

I'm using grub as the boot loader, installed in /boot/grub on the root file system. This is my menu.lst

Code:

default                0

timeout                10



title                Test Kernel build

UUID                21d65db5-00a1-4b97-1e4c-665f20a0887e

kernel                /boot/bzImage root=UUID=21d65db5-00a1-4b97-1e4c-665f20a0887e noinitrd

The Root file system itself contains very little:

Code:

/boot ... containing the kernel (bzImage)

/boot/grub ... containg the grub files

/sbin ... containing "init" (a static build of bash)

/dev ... containing the device files "null" and "console"



... and nothing else.

Any advice welcome.
Thanks

Quote:

Code:

root=UUID=21d65db5-00a1-4b97-1e4c-665f20a0887e

WTF?
Surly that is wrong. Did you try root=/dev/hda1 ?

Quote:

Originally Posted by smeezekitty (Post 3787162)

WTF?
Surly that is wrong. Did you try root=/dev/hda1 ?

Yup tried that, the UUID thing was copied from Ubuntu. I switched to it in an attempt to fix this problem. But given your response it's most likely specific to the Ubuntu kernel.

For my understanding, am I right to think that "root=/dev/hda1" doesn't need me to actually have "/dev/hda1" created on my system?

Yes, you'll need to have the hard drive devices available or you're not going to get very far (I think even if you specify the patitions by their UUID, you still need the device files). You'll probably need a few more like mem and kmem too...

Is there a reason you are not using an initrd?.

Quote:

At the moment I keep getting a kernel panic suggesting that it can't load the root file system.

-- Is the hardware supported by the kernel?
-- Is the memory capable enough without initrd?
-- grub>
root (hd0,0)
kernel /boot/name-of-bzImage root=/dev/sda
initrd /boot/"if-you-have".gz

Hope this helps.

Quote:

Originally Posted by btmiller (Post 3787511)

Yes, you'll need to have the hard drive devices available or you're not going to get very far ... You'll probably need a few more like mem and kmem too

Right will give that a shot then.

How does the kernel use them since the device files won't be available unti the root file system has been loaded ... wont it?

Thanks for all your help

Quote:

Originally Posted by smeezekitty (Post 3787162)

WTF?
Surly that is wrong. Did you try root=/dev/hda1 ?

Not necessarily. This is called persistent device naming. Type blkid to find out yours ;)

Thanks that's really helpful.

Quote:

Originally Posted by ~sHyLoCk~ (Post 3788403)

Not necessarily. This is called persistent device naming. Type blkid to find out yours ;)

That page states that you need to be using initrd for persistent device naming to work so...

As suggested I've created some extra devices and used root=/dev/sda1.
This has got me one step closer but still not there. I'm now getting a panic "Attempt to kill init" but with no message from bash about why...

I replaced bash(sbin/init) with a program which simply prints out numbers starting at 0 and counting up (statically compiled). This doesn't die but doesn't print anything either.

Before I dive into kernel config again, does anyone have any suggestions about what else I've missed to cause this.

My new grub menu.lst is

Code:

default                0

timeout                10



title                Test Kernel build

root                (hd0,0)

kernel                /boot/bzImage root=/dev/sda1 ro noinitrd

My new /dev/ now contains:

Code:

brwxrwxrwx root 5, 1 console

crwxrwxrwx root 1, 2 kmem

crwxrwxrwx root 1, 1 mem

brwxrwxrwx root 1, 3 null

brwxrwxrwx root 1, 1 ram

brwxrwxrwx root 8, 0 sda

brwxrwxrwx root 8, 1 sda1

crwxrwxrwx root 5, 0 tty

crwxrwxrwx root 4, 1 tty1

crwxrwxrwx root 4, 2 tty2

crwxrwxrwx root 4, 3 tty3

crwxrwxrwx root 4, 4 tty4

crwxrwxrwx root 1, 5 zero

Thanks a lot for your time