I just installed Gate Sentry on a Raspberrry PI 3, and I'm able to block https facebook; provided I set the browser to use the proxy on port 8080 and the certificate. It gives me a nice content blocked page after that.
I looked at the configuration and it is using the Dansguardian proxy on port 8080 which then forwards to Squid 3 on port 3127, and if all goes well it forwards to the internet connection on my router.
But I'd like to make this more exclusive, and make a list of servers only to which one is allowed to visit.
So what do I need to read up on in Dansguardian, or Squid3 to black list all sites / servers other than the ones the user is allowed to access? I'd like to setup an deny / allow rule rather than an allow / deny.
This is for purposes of keeping a kid focused on their homework and keeping them off of the social media, during times when it is required for them to focus on such things.