Installing this mod makes the server kick all players when it shuts down. This prevents users from continuing to build inside their local copy of the game.
The mod adds three commands:
/kickall <reason> kicks all players without the nokickall
/reallykickall <reason> kicks all players regardless of their nokickall priv
/kshutdown <reason> kicks all players without the nokickall and shuts down the server
The last command is to enable the server owner to give a reason to the kick. All three commands require the server priv to run.
The mod on Krock's server which shows a formspec to the player that the server has shut down is very handy. It informs the player that the server is down, but you can still walk around, plan your actions for the next day, and take some last screenshots.