First, you'll need to install the web server plugin in the ClearOS marketplace. Yes, I know you don't want a web server running on your router. But there's not much choice, wpad.dat is served via http on port 80. Just don't add a firewall rule allowing connecting to it from outside your network (note that in ClearOS you have to explicitly allow external access to services) and you'll be fine.
Next, in your DNS configuration on your master DNS server (whether that's on the ClearOS server or elsewhere), set up wpad.yourdomain.com pointing at your ClearOS server. If the ClearOS server is providing DNS that's pretty easy, just use the web interface.
Okay, now we're at the end of what the web interface can do for you. We'll need to do some things via ssh now. Make sure ssh access is turned on in your firewall rules (in the GUI), and ssh in as root/yourpassword.
In /var/www/html create a file 'wpad.dat' with these contents:
function FindProxyForURL(url,host)Replace the 192.168.0.1 with the actual address of your ClearOS server, and if you're running the content filter, replace the 3128 with 8080.
return “PROXY 192.168.0.1:3128″;
Now access "http://wpad.your.domain" with your web browser. You should see that file appear. But that's not going to get your auto-proxy working on Chrome, at least, because Chrome wants a MIME type of application/x-ns-proxy-autoconfig rather than text/plain . So let's go set up the MIME type. In the directory /etc/httpd/conf.d create a file 'wpad.conf' with these contents:
And one 'apachectl restart' later, there you are. Your browsers on the network will now auto-configure their proxy settings to go through the ClearOS proxy.