Re: udev: what's up with old /dev ?

Mathieu Segaud
2004-10-13T13:08:47Z

"Harald Dunkel" <harald.dunkel@t-online.de> disait dernièrement que :

> Greg KH wrote:
>> On Tue, Oct 12, 2004 at 10:16:54PM +0200, Harald Dunkel wrote:

> Sorry, somewhere in this thread I had clicked the wrong
> reply button.
>
> Talking about initramfs: I am still trying to become
> familiar with this stuff. I have found a lot of small
> pieces of information (still reading), and the cpio
> stuff in the kernel usr directory. But I have 2 questions:
>
> Why is the initramfs built at the beginning of the
> kernel build procedure? Wouldn't it be more reasonable
> to build it when all kernel modules are available?

because for now, the initramfs built into the kernel is quasi-empty and
isn't used as-is.

>
> And why is it compiled into the kernel at all? The
> README in Documentation/early-userspace says
>
> <quote>
> "Early userspace" is a set of libraries and programs that provide
> various pieces of functionality that are important enough to be
> available while a Linux kernel is coming up, but that don't need to be
> run inside the kernel itself.
> </quote>

the last statement just says it does not run in _kernelspace_ but in
_userspace_.
it has to be in the kernel.
I use it to mount my dm-crypt'd / and no initrd is needed.
(well as I wasn't able to get a small cryptsetup binary, my kernels
are ~1850kB worth of size)

> So why compile it into the kernel? IMHO it would be more
> flexible to load the early-userspace stuff similar to initrd
> via the grub command line. Compiling it into the kernel
> could be optional.

huh, well initrd is / that is mounted over the so-called _rootfs_
initramfs is here to _be_ that rootfs. So no pivot_root needed and the run-it
program included in klibc tarballs takes care of wiping-out everything that
could waste memory into the initramfs before mounting the real /.
If it was to compiled out of the kernel, it would just be an initrd....

rootfs is _needed_ for mounting the real root, so is initramfs.

have a nice day,

Mathieu

--
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February 27, 2001
>From a speech concerning the proposed federal budget.