You can install and upgrade large network of Ubuntu Linux computers very fast. Just use proxy for deb packages.
Install ‘squid-deb-proxy-client’ on workstations. Install ‘squid-deb-proxy’ on server.
Your network should have only one deb proxy, so don’t install the server ‘squid-deb-proxy’ to multiple computers.
Clients find the server automatically on your local network.
If you use “Main server” mirror on clients (workstations), you don’t need to make any settings to neither master nor clients. If you changed mirror, you can change it to default on your clients (workstations) with ‘sudo software-properties-gtk’, “Main Server”, ‘sudo apt-get update’.