Server Administration? Thread - Minecraft

I'm running the Linux minecraft_server.jar file, and had a wonderful afternoon building in the world with my 13 y.o. son. And while it works, there's no administration guide ANYWHERE that I can find....

1) How do I save the game(s)? Do they auto-save - should I just kill the process or press "Ctl-C" ?

2) What's the recommended procedure for a clean shutdown/setup?

3) How do I restrict who can join? (usually, a shared password?)

4) How to find out what options are available?

5) Check for updates? Anyone?

... etc...

PS: Can I run this in a chroot jail?

1)they do auto-save
2) i think that you need to type: "stop" in java
3) i don't think there is something like that (i could be wrong)
4) type: "/help" when you are ingame
5) i don't understand this question

PS: i don't know

Greetz, ReLiFeD