This is how we installed LuxBlender in Blender 2.68, on Ubuntu 12.04:

(adapted from Luxrender wiki site here)

A. Download LuxRender

Download the LuxRender "standalone" for Linux (not OpenCL, here). Only LuxRender 1.0 and 1.1 works well with Blender 2.6x; Older versions do not. Either get LuxRender from the main page or get a weekly build from the forum. Extract the download and put it in a convenient location, we used ~/bin/. Folder name will be something like lux-v1.3-i686-sse2. Inside you will find an executable luxrender and this should work as it is.

B. Get LuxBlend

(This is the application that allow you to integrate with Blender. In step A, you installed the LuxRender, the standalone renderer, two different things)

The very latest development version can be found here: http://src.luxrender.net/luxblend25/archive/tip.zip

Once you have downloaded the zip file and unpacked it, you should see a folder called "src" inside the "luxblend25" folder. Inside the "src" folder there is a folder called "luxrender". Copy this "luxrender" folder (the folder, not just the contents) into your <blender scripts>/addons/ folder. The exact location of the folder we are looking for depends on your operating system. To locate that in your Ubuntu you can type "locate blender | more" and look for the addon folder.(generally on Linux it should be /usr/lib/blender/scripts/addons). You should end up with the following structure: <blender scripts>/addons/luxrender/ which contains an __init__.py file and several other directories.

Then, copy the content of the "preset" folder (inside the "src" folder of luxblend25) in the "preset" folder of Blender: <blender scripts>/presets/, thus giving you the following structure: <blender scripts>/presets/luxrender/engine/ which contains lots of python scripts.

C. Get Pylux

Pylux is a binary add-on for LuxBlend25 which will allow you to do fully integrated rendering inside Blender. On Ubuntu and Linux and Macs OS X, you need two files called pylux.so and liblux.so. You will find these file inside the standalone LuxRender folder you downloaded in step A. Copy those pylux.so and liblux.so files into the folder <blender scripts>/addons/luxrender/.

D. Activate LuxBlend25 within Blender

Fire Blender, after installing the addons, you should see an entry for LuxRender in User Preferences -> Add-Ons -> Render, where you can enable the exporter. Please note that it may take a few seconds for the box to be checked after you click it, so click it once and wait a few seconds while Blender copies some files.

In Blender's Info window (the bar at the top), select LuxRender as your render engine. This changes the available options in the properties window, giving you control over LuxRender's own render settings. Note that some of the panels (such as the dimensions and output panels) don't change as they contain settings that are shared between render engines.

E. Add the path to LuxRender in Blender

Next you need to tell the LuxBlend script where to find LuxRender. In Blender, go to the User Settings (ctrl-alt-U), switch to the Render tab and select the path to the LuxRender installation where you extracted the download in step A. If you followed these instructions the path is ~/bin/lux-v1.3-i686-sse2/. Save user settings (CTRL-U) to have LuxRender as the default render engine and to save the path to the LuxRender installation.

Now if you select the LuxRender renderer and press F12, you should render with LuxRender, the output will be directed on the standalone application LuxRender that you installed in step A.