[Unionfs] UnionFS as root filesystem

[iSteve]

On Wed, 15 Mar 2006 15:13:00 +0100
Olivier Evalet <evaleto at programmers.ch> wrote:

> It could help you,
> 
> linuxrc must have PID==1 to start correctly sbin/init ! Have a look on
> your boot params. Below my config for a 2.6 kernel:
> root=/dev/ram0 init=/linuxrc rw
> 
> I did a complet and small initrd with gentoo-uclibc that mount a unionfs
> backend (debian/ubuntu/gentoo) as rootfs, configure the backend and
> start /sbin/init. 
> 
> 
> Olivier

To expand this a little:
The general idea with initrd is, that you are not guarantedd that your linuxrc
will have pid 1. You, however, need pid 1, since various init implementations
(most commonly the sys v init) behave differently if you have other pid.

Therefore, you should probably let (as suggested above) the initrd only set
root filesystem to /dev/ram0 (it's somewhere in /proc, no idea where; or you
can just set it in bootloader and pray noone changes it) and write yourself a
short /sbin/init in the initrd, which would perform the actual execution of the
init on the target filesystem.