How to change OSX Server update location

I use Caching which is defined in System Preferences / Sharing / Content Caching checkbox. This should put downloads in the /Library/Server/Caching folder. If you have the Software Update service enabled, disable it and enable Caching. You can define where you want the Caching folder to be from that service by clicking the Options button then Edit the Cache Location.

I explained where that is. It is NOT in the Server app. It's in the OS now.

Open System Preferences / Sharing. You will see Content Caching at the bottom of the list of sharing services.