[BusyBox] urgent help at change_root inside of initrd

[Erik Andersen]

On Fri Feb 15, 2002 at 11:52:47AM +0100, Stephan Linz wrote:
> Hi Folks,
> 
> since the last two days I've tried to make a so named "change_root" mechanism 
> with support of kernels sysctrl (/proc/sys/kernel/real-root-dev) inside of a 
> minimal initrd image. I use kernel 2.2.19 so I can't use the newer 
> "pivot_root" mechanism. In kernel documentation initrd.txt says I have to 
> write the major-minor code of the new root FS into the virtuell file 
> /proc/sys/kernel/real-root-dev, but nothing is going on. Here my boot 
> strategy (all things at x86 plattform):
> 
> BIOS boots from first master IDE device (LILO). LILO loads kernel and initrd 
> image. Kernel mounts initrd image as first root FS in ramdisk(/dev/ram0); in 
> lilo.conf is standing: append="root=/dev/ram init=/linuxrc rw". Initrd image 

Lose the root=/dev/ram init=/linuxrc stuff.  The initrd will do
what you want without that...

> covers a small busybox, /linuxrc is a shellscript and has to mount /dev/hda1, 
> extract the real root FS from a tarball to /dev/ram1, unmount /dev/hda1 and 
> mount /dev/ram1 as new root FS. So at the end of /linuxrc I write:
> 
> mount -t proc /proc /proc
> echo 0x101 >/proc/sys/kernel/real-root-dev
> exec /sbin/init

Drop the mount /proc and the exec.  Just leave the echo, and let
the /linuxrc script exit, at which point the kernel will mount
/dev/ram1 as root, remount your initrd as /initrd in your new
root (if you have that directory), and exec /sbin/init on
/dev/ram1 (which is now your root device)

 -Erik

--
Erik B. Andersen             http://codepoet-consulting.com/
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