Say if you have Gollum running on http://192.168.0.1:4567 and you have a reverse proxy (ex: www.abc.com) in front of it such that you want to allow the team to access it on http://www.abc.com/docs. You need to setup a ProxyPass on the reverse proxy. Say in Apache.

<VirtualHost *:80>
  ServerName www.abc.com
  ProxyPass /docs http://192.168.0.1:4567/docs
  ProxyPassReverse /docs http://192.168.0.1:4567/docs
</VirtualHost>

It would work but the site asset path would be incorrect. So you need to specify the base path when you start Gollum.

gollum --base-path docs

If you are using Rack with Gollum, you could add the base path settings to wiki_options in the config.ru.

#!/usr/bin/env ruby
require 'rubygems'
require 'gollum/app'
gollum_path = File.expand_path(File.join(File.dirname(__FILE__), './')) # CHANGE THIS TO POINT TO YOUR OWN WIKI REPO
Precious::App.set(:gollum_path, gollum_path)
Precious::App.set(:default_markup, :markdown) # set your favorite markup language
Precious::App.set(:wiki_options, {:live_preview => false, :universal_toc => false, :user_icons => 'gravatar', :base_path => 'docs'})
module Precious
  class App < Sinatra::Base
  ...

Done =)

References:

• Gollum – Add Git identity by running Gollum as a Rack appliaction
• Using Gollum with Rack
• ProxyPass with Gollum wiki