If I self host a Lemmy instance for just myself and maybe a few friends are there any risks?
Looking to maybe self host my own instance, I'm still learning about the fediverse. If a different instance that I federate with hosts something illegal are there risks to me? Is anything from other instances hosted on my server like a copy of it? Or would I only end up hosting things my users post? I'm paranoid and sorry if this is a silly question.
Federation is implemented by copying the content from other servers to your database and file system, so if your users subscribe to something from a different server it will be copied to your server.
But it will be only served to your users, not to the public. Only the communities hosted on your instance will be served to the public.
It depends on the software. Some proxy all content from remote servers so you only connect to your home server (Mastodon). Others don't, instead they make clients load remote content themselves (Lemmy). If you use browser client you can see all the connections being made.
You can if someone else subscribed to it in the past. If nobody ever did, then that community is unknown to kbin and you won't find any data on it whether you're logged in or not.
My understanding is that instances have worker threads that continually pull new data from linked communities (the ones at least 1 person is subscribed to). It should be almost instant but recently it's sometimes delayed due to huge influx of traffic.