Re: Initrd problem with 2.6 kernel

Re: Initrd problem with 2.6 kernel

[Andrey Borzenkov]

> There is a chicken and egg problem with initrd on 2.6. When
> root=/dev/xxx is passed to kernel, kernel will call try_name, which
> uses /sys/block/drive/dev, to find out the device number for ROOT_DEV.
> The problem is /sys/block/drive may not exist if the driver is loaded
> by /linuxrc in initrd. As the result, /linuxrc can't use
> /proc/sys/kernel/real-root-dev to determine the root device number.

{pts/1}% grep \"/sys\" *
do_mounts.c:    sys_mkdir("/sys", 0700);
do_mounts.c:    if (sys_mount("sysfs", "/sys", "sysfs", 0, NULL) < 0)
do_mounts.c:    sys_umount("/sys", 0);
do_mounts.c:    sys_rmdir("/sys");

or do you mean something different?

-andrey

Re: Initrd problem with 2.6 kernel

[H. J. Lu]

On Fri, Aug 08, 2003 at 08:49:16PM +1000, Herbert Xu wrote:
> H. J. Lu <hjl@lucon.org> wrote:
> > There is a chicken and egg problem with initrd on 2.6. When
> > root=/dev/xxx is passed to kernel, kernel will call try_name, which
> > uses /sys/block/drive/dev, to find out the device number for ROOT_DEV.
> > The problem is /sys/block/drive may not exist if the driver is loaded
> > by /linuxrc in initrd. As the result, /linuxrc can't use
> > /proc/sys/kernel/real-root-dev to determine the root device number.
> 
> You can replicate the sysfs probing in userspace.  I did that in
> Debian initrd-tools 0.1.51.

It sounds a good idea. I will give it a try.

Thanks.

H.J.

Re: Initrd problem with 2.6 kernel

[Herbert Xu]

H. J. Lu <hjl@lucon.org> wrote:
> There is a chicken and egg problem with initrd on 2.6. When
> root=/dev/xxx is passed to kernel, kernel will call try_name, which
> uses /sys/block/drive/dev, to find out the device number for ROOT_DEV.
> The problem is /sys/block/drive may not exist if the driver is loaded
> by /linuxrc in initrd. As the result, /linuxrc can't use
> /proc/sys/kernel/real-root-dev to determine the root device number.

You can replicate the sysfs probing in userspace.  I did that in
Debian initrd-tools 0.1.51.
-- 
Debian GNU/Linux 3.0 is out! ( http://www.debian.org/ )
Email:  Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: Initrd problem with 2.6 kernel

[Andrew Morton]

"H. J. Lu" <hjl@lucon.org> wrote:
>
> There is a chicken and egg problem with initrd on 2.6. When
> root=/dev/xxx is passed to kernel, kernel will call try_name, which
> uses /sys/block/drive/dev, to find out the device number for ROOT_DEV.
> The problem is /sys/block/drive may not exist if the driver is loaded
> by /linuxrc in initrd. As the result, /linuxrc can't use
> /proc/sys/kernel/real-root-dev to determine the root device number.

You should be able to use the numeric identifier:

	root=03:02

that's major:minor, and it recently changed.  In 2.6.0-test2 that would be
"0302".

Initrd problem with 2.6 kernel

[H. J. Lu]

There is a chicken and egg problem with initrd on 2.6. When
root=/dev/xxx is passed to kernel, kernel will call try_name, which
uses /sys/block/drive/dev, to find out the device number for ROOT_DEV.
The problem is /sys/block/drive may not exist if the driver is loaded
by /linuxrc in initrd. As the result, /linuxrc can't use
/proc/sys/kernel/real-root-dev to determine the root device number.


H.J.