The current switch_root can only switch to a new root that is the root
of a mount point.
This patch adds support for "subroots", where the new root is somewhere
below a mount point. It does this by adding in a few extra steps to
chroot into the subroot after the enclosing partition has been moved
and entered.
This will be used by OLPC, who sort-of have 2 copies of Fedora stored
on a single partition under different directory trees, where the
initramfs decides which one to boot into.
Shift some required functionality from switch_root.c to init.
String manipulation and filtering, and testing for the existence of init
is easier in the init script than in C.
The switch_root shell script did not work with bash-4.0-2, because
"exec" gets the real path of the executable which is then
"/sysroot/lib/ld-linux.so.2" instread of "./lib/ld-linux.so.2".
Also the required chroot binary might live in /usr/bin, which can
be mounted later.
Here is the switch_root code from nash, which can be stripped down
further, but which works.
>From f1b1e4f8694104f007e4483c36b0bf40a5760167 Mon Sep 17 00:00:00 2001
From: Harald Hoyer <harald-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Date: Wed, 4 Mar 2009 13:41:07 +0100
Subject: [PATCH] replace switch_root shell script with binary
The switch_root shell script did not work with bash-4.0-2, because
"exec" gets the real path of the executable which is then
"/sysroot/lib/ld-linux.so.2" instead of "./lib/ld-linux.so.2".
Also the required chroot binary might live in /usr/bin, which can
be mounted later.
Here is the switch_root code from nash, which can be stripped down
further, but which works.
Daniel Drake