post_install() {

        getent group chrony &>/dev/null || groupadd -g 130 chrony >/dev/null
        getent passwd chrony &>/dev/null || useradd -u 130 -g chrony -d /var/lib/chrony -c 'Network Time Protocol' -s /bin/false chrony >/dev/null
}

post_upgrade() {

        getent group chrony &>/dev/null || groupadd -r -g 130 chrony >/dev/null
        getent passwd chrony &>/dev/null || useradd -r -u 130 -g chrony -d /var/lib/chrony -c 'Network Time Protocol' -s /bin/false chrony >/dev/null
        chown -R 130:130 /var/lib/chrony
}

post_remove() {

        getent passwd chrony &>/dev/null || /usr/sbin/userdel chrony 2>/dev/null
        getent group chrony &>/dev/null || /usr/sbin/groupdel chrony 2>/dev/null
}

op=$1
shift
$op $*