Running Gazebo on a headless OpenStack instance: "Unable to create glx visual"

edit

I am trying to run Gazebo and the associated gazebo_ros package on a headless OpenStack instance, and using the gzweb software to access it through a browser. I do not need gzclient to be running on this instance at all. When I run the following command:

~$ gazebo

it shows the following error:

Error [RenderEngine.cc:680] Unable to create glx visual

Warning [RenderEngine.cc:88] Unable to create X window. Rendering will be disabled

Other similar questions on the ROS questions site (such as here and here) suggest using DISPLAY=:0, but when I add this into the command as follows:

DISPLAY=:0 gazebo

it gives me a different error:

Error [RenderEngine.cc:665] Can't open display: :0

Any suggestions on how to remedy this issue? Any help would be greatly appreciated.