$ sudo apt-get update
$ sudo apt-get install lua-rex-posix 

lua-rex-posix is installed in your system.

Make ensure the lua-rex-posix package were installed using the commands given below,

$ sudo dpkg-query -l | grep lua-rex-posix *

You will get with lua-rex-posix package name, version, architecture and description in a table

lua-rex-posix package basic information: