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From: Chris Lingard <chris@ukpost.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: initrd help -- umounts root after pivot_root
Date: Fri, 31 Oct 2003 18:47:47 +0000
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On Friday 31 October 2003 12:18 am, John R Moser wrote:
> Been trying with 2.4.20, 2.4.22, 2.6.0-test9, how the heck do I get this
> to work?
> I set everthing up on /dev/shm type tmpfs, then
> cd /dev/shm
> mkdir initrd
> pivot_root . initrd

Might be better to do something like:

mount -t devfs  none  /dev
mount -t proc none /proc
mkdir  -p  ram
mount -t tmpfs tmpfs /ram
cd /ram
mkdir proc  cdrom
mount  -t proc  none /ram/proc
/mount_cdrom

This is the start of my linuxrc script and creates the future root at /ram

> Of course, the kernel unmounts / and then swears that it can't find init
> when the linuxrc exits.
>
> The documentation says that linuxrc should pivot_root to the real root in
> Documentation/initrd.txt so I thought that's what the script sholud do.
> Apparently the doc is bad/old.

man pivot_root

mkdir initrd
sbin/pivot_root  .  initrd
mount devfs -t devfs /dev
exec /usr/sbin/chroot . /sbin/init  <dev/console >dev/console 2>&1

(These is no automatic call to /sbin/init)

The documentation is bad insofar as root=/dev/rd/0 now fails

Also you will need to search for a patch to umount your old /initrd.  Please
feel free you email me direct for a very unofficial patch to linux-2.4.22

Chris Lingard