#!/bin/sh -e
# xchroot DIR [CMD...] - chroot into a Void (or other Linux) installation

fail() {
	printf '%s\n' "$1" 1>&2
	exit 1
}

if [ "$(id -u)" -ne 0 ]; then
	fail 'xchroot needs to run as root'
fi

case "$1" in
	/*) CHROOT=$1; shift;;
	*) fail 'no absolute chroot dir given';;
esac

[ -d "$CHROOT" ] || fail 'not a directory'
[ -d "$CHROOT/dev" ] || fail 'no /dev in chroot'
[ -d "$CHROOT/proc" ] || fail 'no /proc in chroot'
[ -d "$CHROOT/sys" ] || fail 'no /sys in chroot'

mount --rbind /dev "$CHROOT/dev"
mount --rbind /proc "$CHROOT/proc"
mount --rbind /sys "$CHROOT/sys"

cleanup() {
	umount -R "$CHROOT/dev" "$CHROOT/proc" "$CHROOT/sys"
}

trap cleanup EXIT INT

if [ -f "$CHROOT/$SHELL" ]; then
	INNER_SHELL="$SHELL"
elif [ -f "$CHROOT/bin/bash" ]; then
	INNER_SHELL="/bin/bash"
else
	INNER_SHELL="/bin/sh"
fi

chroot "$CHROOT" ${@:-$INNER_SHELL}