rocklinux/target/rescue/contrib/init-boot-cycle

#!/bin/sh
#
# This boot-script boots a system found in a given LVM
# logical volume.
# In case of trouble it passes control to the original init
# thus giving gettys and running /etc/boot.d/*
# It is included in system.tar.bz2. For usage information
# see below.
#
# Plan:
# -read kernel append line by /proc/1/environ and evaluate
#  ROOTLV (should point to /dev/vg00/lvroot00 or kind of)
# -mount ROOTLV to /mnt/root (ro)
# -pivot_root to /mnt/root
# -chroot into /mnt/root and exec init
#
# mini-howto of usage:
#
# -build your rescue target (you get system.tar.bz2 and initrd.img)
# -put system.tar.bz2 in /rescue onto your boot-device-fs
# -optional: put overlay.tar.bz2 in /rescue onto your boot-device-fs
# -get a kernel and arm your favorite boot-loader
# -pass stage2init=/sbin/init-lvm-cycle to the kernel
# -pass ROOTLV=/dev/vgXX/lvYYY to the kernel
# -don't forget to pass initrd.img to your boot loader
# -and boot
#
# you can omit ROOTLV parameter to get the rescue system
#
# see contrib/menu.lst-example
#
# Tobias Hintze <th@rocklinux.org> (c) 2004
#

shopt -s execfail

fail() {
	echo "$1"
	echo
	echo "continuing inside rescue-stage2..."
	exec /sbin/init
	echo "failed to execute /sbin/init."
	echo "all that i can give to you is that shell."
	echo
	exec sh
}

fail_shell() {
	echo "$1"
	echo
	echo "try to fix the problem and terminate this shell."
	echo
	sh
}

# some init
export PATH=/sbin:/bin:/usr/sbin:/usr/bin
mount -t proc none /proc
mkdir /mnt/boot /mnt/root
mount --move /old_root/mnt_boot /mnt/boot
umount -n /old_root

# read ROOTLV and additional arguments (e.g. runlevel)
ROOTLV=`cat /proc/1/environ | tr '\0' '\n' | grep -i ^rootlv | cut -d= -f2`
[ -z "$ROOTLV" ] && fail "no ROOTLV specified."

INITARGS=""
RUNLEVEL=`cat /proc/1/environ | tr '\0' '\n' | grep -i ^runlevel | cut -d= -f2`
if [ ! -z "$RUNLEVEL" ] ; then
	echo "runlevel specified. passing $RUNLEVEL to init."
	INITARGS="$RUNLEVEL"
fi

# scan for and activate volume groups
[ -f /etc/conf/lvm2wrap ] && . /etc/conf/lvm2wrap
vgscan && vgchange -ay
[ -e "$ROOTLV" ] || fail "specified ROOTLV does not exist."

# mount new root
mount -o ro $ROOTLV /mnt/root
cd /mnt/root

# move mounts inside new root
[ -d dev ] || fail_shell "dev/ mountpoint does not exist."
mount --move /dev dev
[ -d mnt/boot ] || fail_shell "mnt/boot/ mountpoint does not exist."
mount --move /mnt/boot mnt/boot

[ -d mnt/oldroot ] || fail_shell "mnt/oldroot/ mountpoint does not exist."
umount /proc

# switch to new root and exec init
mknod dev/initctl p
pivot_root . mnt/oldroot
exec chroot . sh -c "umount /mnt/oldroot ; exec /sbin/init $INITARGS" \
	<dev/console >dev/console 2>&1
fail "pivot_root failed..."