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SubjectRe: initramfs for /dev/console with udev?
On Thu, Nov 03, 2005 at 11:38:09AM -0600, Rob Landley wrote:
> No, you just need a statically linked init program. (Which can be a shell
> script using a statically linked shell. For testing purposes it can be
> statically linked against glibc, it'll just be a bloated pig.)

I'll try that.

> You also have the option of putting a single static node (console) in the /dev
> directory you're going to overmount. It shouldn't hurt anything at present.
> And if nothing else, it'll confirm where it's trying to get the sucker
> from...

Well, that only works with root permissions.

> > Seems
> > like I'll have to do some deeper investigation of klibc; last time I
> > looked it didn't even compile for ARCH=um.
>
> Klibc didn't, or the kernel didn't?

The kernel works pretty good with 2.6.14; I can now do 'make world' in
PTXdist and get a rootfs for the ARM and do 'make world NATIVE=1' and
'make run NATIVE=1' and the same thing builds for x86 and starts in a
console. klibc didn't compile for ARCH=um.

> > Is there any other known possibility to get just these two device nodes
> > in an automatic way?
>
> From initramfs, you could try:
>
> mount -t sysfs /sys /sys
> CDEV=`cat /sys/class/tty/console`
> mknod /dev/console c $(echo $CDEV | sed 's/:.*//') \
> $(echo $CDEV | sed 's/.*://')
>
> Bit of a chicken and egg problem if it refuses to run /init if it's not
> already there, though. We're heading towards fully dynamic devices, but not
> quite there yet...

All that means that I need some libc and tools linking against it (or
static tools)...

> > I'm trying to get rid of devfs, and udev works just
> > fine. The only thing not solved yet is how to get the beast started
> > without /dev/console and /dev/null. I don't want to create the nodes
> > statically, because that's only possible with root permissions.
>
> You don't need root access to make an initramfs configuration text file. :)

That was the idea ;) But it seems that if I buy initramfs I'll have to
buy doing the mknod and rootfs mounting stuff from early userspace as
well...

> > Some background: I'm building root filesystems for embedded systems with
> > PTXdist; the user is able to build the whole thing without root
> > permissions; either with a cross compiler and mount it via NFS or build
> > a JFFS2 image, or, with one switch, build and run it with an uml kernel.
>
> I did something like that, only from scratch:
> http://www.landley.net/code/firmware
>
> I'll probably release version 0.8.10 later today. (Still need to make an
> installer for the bootable version before I can call it 0.9...)

I'll have a look :)

Thx,

Robert
--
Dipl.-Ing. Robert Schwebel | http://www.pengutronix.de
Pengutronix - Linux Solutions for Science and Industry
Handelsregister: Amtsgericht Hildesheim, HRA 2686
Hannoversche Str. 2, 31134 Hildesheim, Germany
Phone: +49-5121-206917-0 | Fax: +49-5121-206917-9

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