I've got Selenium server running, controlling Chrome, Chromium and Firefox on a headless Linux system.

Install Dependencies

emerge -av dev-php/pear
pear channel-discover pear.phpunit.de
pear install phpunit/PHPUnit_Selenium

apt-get install chromium-chromedriver firfox php5-cli php5-curl php5-json
wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
dpkg -i google-chrome-stable_current_amd64.deb

Install Selneium

mkdir ~/selenium
cd selenium
wget ...

Configure It?

#!/bin/bash

cd $(dirname $(readlink -f $0 ))

export DISPLAY=:90

nohup java \
	-jar selenium.jar \
	-log selenium.log \
	-maxSession 8 \
	-browserTimeout 64 \
	>selenium.out 2>&1 &
	
echo $! >selenium.pid