#!/bin/sh

set -euo pipefail

PATH=/sbin:/bin:/usr/sbin:/usr/bin

/bin/mount -t proc proc /proc
/bin/mount -t sysfs sysfs /sys
grep -w "/dev" /proc/mounts >/dev/null || /bin/mount -t devtmpfs none /dev

[ -z "${CMDLINE+x}" ] && CMDLINE=`cat /proc/cmdline`
for arg in $CMDLINE; do
	optarg=`expr "x$arg" : 'x[^=]*=\(.*\)' || echo ''`
	case $arg in
		root=*)
			ROOT_RODEVICE=$optarg ;;
		rootfstype=*)
			ROOT_ROFSTYPE=$optarg ;;
	esac
done

ROOT_ROMOUNTPARAMS="-t $ROOT_ROFSTYPE -o noatime,nodiratime $ROOT_RODEVICE"
if ! /bin/mount $ROOT_ROMOUNTPARAMS /media/rfs/ro 2>/dev/null && \
	[ "x-o bind /" == "x$ROOT_ROMOUNTPARAMS" ] || \
	log "Could not mount $ROOT_RODEVICE, bind mounting..." && \
	! /bin/mount -o bind / /media/rfs/ro; then
	fatal "Could not mount read-only rootfs"
fi

if ! /bin/mount -o remount,ro /media/rfs/ro; then
	fatal "Could not remount read-only rootfs as read only"
fi

if ! /bin/mount PARTUUID=f1326040-5236-40eb-b683-aaa100a9afcf /media/rfs/rw -t auto -o relatime,nosuid,nodev ; then
	fatal "Could not mount read-write rootfs"
fi

mkdir -p /media/rfs/rw/upperdir /media/rfs/rw/work
/bin/mount -t overlay overlay -o lowerdir=/media/rfs/ro,upperdir=/media/rfs/rw/upperdir,workdir=/media/rfs/rw/work /mnt

mkdir -p /mnt/media/rfs/ro /mnt/media/rfs/rw
/bin/mount -n --move /media/rfs/ro /mnt/media/rfs/ro
/bin/mount -n --move /media/rfs/rw /mnt/media/rfs/rw

/bin/mount -n --move /proc /mnt/proc
/bin/mount -n --move /sys /mnt/sys
/bin/mount -n --move /dev /mnt/dev

cd /mnt
exec chroot /mnt /sbin/init || fatal "Couldn't chroot, dropping to shell"