Selenium firefox Xvfb

How to specify web driver that start firefox in background or
something ? Actually i want to run these test on continuous
integration server. which does not have X. Is it possible ? should i
use Xvfb or something ? I tried running a test on server it gives
following error.
    [junit] Testcase: testLogin(com.*.framework.ui.LoginTest):  Caused
an ERROR
    [junit] org.openqa.selenium.WebDriverException: Failed to connect
to binary FirefoxBinary(/usr/bin/firefox) on port 7055; process output
follows:
    [junit] Error: no display specified
    [junit] Error: no display specified
    [junit]
    [junit] System info: os.name: 'Linux', os.arch: 'i386',
os.version: '2.6.18-92.1.13.el5', java.version: '1.6.0_10-rc'
    [junit] Driver info: driver.version: firefox
    [junit] System info: os.name: 'Linux', os.arch: 'i386',
os.version: '2.6.18-92.1.13.el5', java.version: '1.6.0_10-rc'
    [junit] Driver info: driver.version: firefox
    [junit] org.openqa.selenium.WebDriverException:
org.openqa.selenium.WebDriverException: Failed to connect to binary
FirefoxBinary(/usr/bin/firefox) on port 7055; process output follows:
    [junit] Error: no display specified
    [junit] Error: no display specified



use Xvfb: firefox needs a proper DISPLAY in order to work.