RHEL 6 install Xvfb

xorg-x11-server-Xfvb is not in the standard RHEL 6 repositories.  If you wish to install it you will need to enable the repository.  Perform the following:-

# subscription-manager repos --enable rhel-6-server-optional-rpms
Repo rhel-6-server-optional-rpms is enabled for this system.
# yum search xvfb
Loaded plugins: product-id, security, subscription-manager
This system is receiving updates from Red Hat Subscription Management.
rhel-6-server-cf-tools-1-rpms                                       | 2.8 kB     00:00
rhel-6-server-optional-rpms                                         | 3.5 kB     00:00
rhel-6-server-optional-rpms/primary_db                              | 2.7 MB     00:00
rhel-6-server-rpms                                                  | 3.7 kB     00:00
rhel-6-server-rpms/primary_db                                       |  25 MB     00:03
==================================== N/S Matched: xvfb ====================================
xorg-x11-server-Xvfb.x86_64 : A X Windows System virtual framebuffer X server.

  Name and summary matches only, use "search all" for everything.
# yum install xorg-x11-server-Xvfb
Loaded plugins: product-id, security, subscription-manager
This system is receiving updates from Red Hat Subscription Management.
rhel-6-server-cf-tools-1-rpms                                       | 2.8 kB     00:00
rhel-6-server-optional-rpms                                         | 3.5 kB     00:00
rhel-6-server-rpms                                                  | 3.7 kB     00:00
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package xorg-x11-server-Xvfb.x86_64 0:1.13.0-23.1.el6_5 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

===========================================================================================
 Package                Arch     Version               Repository                     Size
===========================================================================================
Installing:
 xorg-x11-server-Xvfb   x86_64   1.13.0-23.1.el6_5     rhel-6-server-optional-rpms   775 k

Transaction Summary
===========================================================================================
Install       1 Package(s)

Total download size: 775 k
Installed size: 1.9 M
Is this ok [y/N]: y
Downloading Packages:
xorg-x11-server-Xvfb-1.13.0-23.1.el6_5.x86_64.rpm                   | 775 kB     00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : xorg-x11-server-Xvfb-1.13.0-23.1.el6_5.x86_64                           1/1
rhel-6-server-rpms/productid                                        | 1.7 kB     00:00
  Verifying  : xorg-x11-server-Xvfb-1.13.0-23.1.el6_5.x86_64                           1/1

Installed:
  xorg-x11-server-Xvfb.x86_64 0:1.13.0-23.1.el6_5

Complete!