I used nutch to crawl sites on a single domain. After the crawl was complete I tried to build a LinkDb. The LinkDb was empty.
It comes up that this happens because the invertlinks command ignores internal links to the same domain by default.
Unfortunately the LinkDb class doesn't tell anything about that. So it was hard to find out why the LinkDb was empty.
I suggest to add an information for the user when the invertlinks command is ignoring internal links.