chroot wrapper script

gochroot

#!/bin/bash

# Change this to the parent folder that holds all chroots
CHROOT_ROOT=/scratch/chroot

# DO NOT CHANGE!
chrootname="$1"
chrootdir="$CHROOT_ROOT/$chrootname"
chrootlock="$CHROOT_ROOT/$chrootname.lock"
pid=$$

usage() {
	cat <<EOF
Usage: ${0##*/} chroot-name [args]

    -h          Print this help message

EOF
}

check_mount() {
	cat /proc/mounts | grep $1 >/dev/null 2>&1
	return $?
}

check_umount() {
	if check_mount $1; then
		umount $1
		return $?
	fi
}

die() {
	echo >&2 $1
	exit 1
}

mount_all() {
	if [[ ! -d "$chrootdir" ]]; then
		die "No such chroot: $chrootname"
	fi

	if ! check_mount "$chrootdir/dev"; then
		mount --bind /dev "$chrootdir/dev"
	fi

	if ! check_mount "$chrootdir/dev/pts"; then
		mount --bind /dev/pts "$chrootdir/dev/pts"
	fi

	if ! check_mount "$chrootdir/proc"; then
		mount -t proc none "$chrootdir/proc"
	fi

	if ! check_mount "$chrootdir/sys"; then
		mount -t sysfs none "$chrootdir/sys"
	fi
}

umount_all() {
	check_umount "$chrootdir/sys"
	check_umount "$chrootdir/proc"
	check_umount "$chrootdir/dev/pts"
	check_umount "$chrootdir/dev"
}

clean_lock() {
	pids=$(cat $chrootlock)
	rm -f $chrootlock
	for p in $pids; do
		if ps -p $p >/dev/null; then
			echo $p >> $chrootlock
		fi
	done
	touch $chrootlock
}


if [[ -z $1 || $1 = @(-h|--help) ]]; then
	usage
	exit $(( $# ? 0 : 1 ))
fi

(( EUID == 0 )) || die "This script must be run with root privileges"
shift

# Add lock
if [[ ! -f "$chrootlock" ]]; then
	mount_all
	echo $pid > "$chrootlock"
else
	clean_lock
	echo $pid >> "$chrootlock"
fi

# Go chroot!
chroot "$chrootdir" /bin/bash -l "$@"

# Remove lock
sed -i '/'$pid'/d' "$chrootlock"
clean_lock
if [[ ! -s "$chrootlock" ]]; then
	rm -f "$chrootlock"
	umount_all
fi