#!/bin/bash
# Utility script to chroot into a root filesystem of a foreign
# architecture
set -e

fail() {
    echo "$1" >&2
    exit 1
}

rootfs="$1"

[ -n "$rootfs" ] || fail "Usage: $(basename "$0") <directory>"
[ -e "$rootfs" ] || fail "$rootfs does not exist"
[ "$EUID" -eq 0 ] || fail "$(basename "$0") must be run as root"

# Unmount and remove any temporary files
#
cleanup() {
    set +e
    fuser --kill -SIGTERM "$rootfs"
    sleep 2
    fuser --kill -SIGKILL --verbose "$rootfs"
    umount -l "$rootfs/proc" 2> /dev/null
    umount -l "$rootfs/sys" 2> /dev/null
    umount -l "$rootfs/dev/pts" 2> /dev/null
    umount -l "$rootfs/dev" 2> /dev/null
    trap - 0 1 2 3 6
}
trap cleanup 0 1 2 3 6

mount -t proc chproc "$rootfs/proc"
mount -t sysfs chsys "$rootfs/sys"
mount -t devtmpfs chdev "$rootfs/dev"
mount -t devpts chpts "$rootfs/dev/pts"

echo "chrootfs: chrooting into $rootfs" 1>&2
LANG=C LC_ALL=C chroot "$rootfs"
echo "chrootfs: cleaning up" 1>&2
cleanup
echo "chrootfs: done" 1>&2