postinst is in nginx-light 1.14.0-0ubuntu1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33  | #!/bin/sh
set -e
case "$1" in
  abort-upgrade|abort-remove|abort-deconfigure|configure)
    ;;
  triggered)
    if [ -x /etc/init.d/nginx ]; then
      if [ -s /run/nginx.pid ] && pidof /usr/sbin/nginx >/dev/null; then
        echo "Triggering nginx reload ..."
        invoke-rc.d nginx reload || true
      fi
    fi
    exit 0
    ;;
  *)
    echo "postinst called with unknown argument \`$1'" >&2
    exit 1
    ;;
esac
if [ -x /etc/init.d/nginx ]; then
  if [ -f /run/nginx.pid ] && pidof /usr/sbin/nginx >/dev/null; then
    invoke-rc.d nginx upgrade || invoke-rc.d nginx restart
    exit $?
  else
    invoke-rc.d nginx start || exit $?
  fi
fi
exit 0
 |