postinst is in nginx-core 1.4.6-1ubuntu3.9.
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 34 35 36 37  | #!/bin/sh
set -e
case "$1" in
  abort-upgrade|abort-remove|abort-deconfigure|configure)
    ;;
  *)
    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
    NGX_PID=`cat /run/nginx.pid`
    if kill -s USR2 $NGX_PID 2>/dev/null; then
      while [ ! -s /run/nginx.pid.oldbin ] || [ ! -s /run/nginx.pid ]; do
        cnt=`expr $cnt + 1`
        if [ $cnt -gt 10 ]; then
          kill -s KILL $NGX_PID
          invoke-rc.d nginx start
          exit 0
        fi
        sleep 1
      done
      NGX_OLD_PID=`cat /run/nginx.pid.oldbin`
      kill -s QUIT $NGX_OLD_PID
    fi
  else
    invoke-rc.d nginx start || exit $?
  fi
fi
exit 0
 |