Guys, I want to make a new server. It's okay, I can do it, but I can't change my map.
I have a nice Mountain map but I can't change the map. It gives me a random map. =/
Now that that's all sorted out, the problem is likely that you have the map file, but it's not renamed to server_level.dat. Make sure it's names as server_level.dat, and put it in the server folder. If you've already done this, then the map file is corrupted and cannot be read by the server, thus generating a random map in its place. In that case, we can't help you.