Hallo alles,
We finally got a VPS running a YaCy instance on Yggdrasil, an overlaynet that’s basically the testing ground for ideas that are too young to go into cjdns. I want to set up a new DHT there, so that the nodes can communicate without leaking URLs to freeworld that would be inaccessible anyway.
Is there a way to do this? As far as I can tell, I can simply copy the network definition file and add a couple of seedlists created by other YaCy instances on the network?
Yes that can be done.
The YaCy network is defined in the YaCy network definition file. For the ‘freeworld’ network this is in defaults/yacy.network.freeworld.unit.
Just have a look at the different ‘yacy.network.xxx’-files in defaults.
The network is selected by setting the attribute network.unit.definition in defaults/yacy.init to your network file.
A network definition is simple: its just a combination of a name of the network together with a IP pattern that must apply for your network. For a start, do copy-paste of existing files.
There are some additional settings for the shape of the DHT and bootstraping seed lists. If you want to spawn up a peer-to-peer network you must solve a little bit a chicken-egg-problem: start with one peer, make that peer into a principal of that network and then assign your seedlist location to the bootstrap file list.
Please have a look into all mentioned files, there are plenty of comments which explain the attributes.
I have tried this while waiting for your reply (the documentation is excellent), and the designated bootstrap node kept saying it’s a “Virgin”, even after I set up seedlist upload.
I ran another client in parallel, and it says that the seedlist contains 0 nodes, even though there’s something in the file. 
In addition, is there a way to make YaCy only index websites within an IP range? The network definition seems to only provide this for access control.