lubuntu-default-session software package provides Set default session to Lubuntu, you can install in your Ubuntu 14.04 LTS (Trusty Tahr) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install lubuntu-default-session
lubuntu-default-session is installed in your system.
Make ensure the lubuntu-default-session package were installed using the commands given below,
$ sudo dpkg-query -l | grep lubuntu-default-session *
You will get with lubuntu-default-session package name, version, architecture and description in a table
| Distro | Ubuntu 14 04 lts trusty tahr |
| Section | X Window System software |
| Package | lubuntu-default-session |
| Version | 0.39 |
| Description | Set default session to Lubuntu |
| Sub Section | x11 |