post_install() {
  grep -Pq '^nrpe\s+' /etc/services || \
    echo "nrpe             5666/tcp" >> /etc/services
}

post_upgrade() {
  post_install $1
}

post_remove() {
  # remove the line added to /etc/services
  sed -e '/nrpe             5666\/tcp/d' \
      -i /etc/services || true
}
