post_install(){
  if ! getent group vnstat &>/dev/null; then
    groupadd -r vnstat >/dev/null
  fi
  if ! getent passwd vnstat &>/dev/null; then
    useradd -r -g vnstat -G adm -d /var/lib/vnstat -s /bin/nologin vnstat >/dev/null
  fi
  if ! groups vnstat | grep adm &>/dev/null; then
    gpasswd -a vnstat adm >/dev/null
  fi
  vnstat_shell=$(getent passwd vnstat | cut -d: -f7)
  if [ "$vnstat_shell" != '/bin/nologin' ]; then
    chsh -s /bin/nologin vnstat &>/dev/null
  fi
  if [[ ! -d /var/lib/vnstat ]]; then
    mkdir -p /var/lib/vnstat
  fi
  chmod 700 /var/lib/vnstat
  chown vnstat:vnstat /var/lib/vnstat
}

post_upgrade(){
  post_install
}

post_remove(){
  echo "-- You may want to remove /var/lib/vnstat"
  if getent passwd vnstat &>/dev/null; then
    userdel vnstat >/dev/null
  fi
  if getent group vnstat &>/dev/null; then
    groupdel vnstat >/dev/null
  fi
}