I read a short story years ago and would like to find it again. It was about a world ship of mysterious origin traveling for millions of years. There was a group of (presumably) humans living near the engines of the ship. This group was fighting a war against some sort of non-sentient organisms. There was also some sort of coup near the control center, but the book did not go into much detail about that.
That's all I can think of. I would appreciate some help figuring out which story this is. Thanks.