"Turn your forum on and off"

[Lynne]

vboptions > server settings ? *NIX server load limit

vBulletin can read the overall load of the server on certain *NIX setups (including Linux).

This allows vBulletin to determine the load on the server and processor, and to turn away further users if the load becomes too high.

If you do not want to use this option, set it to 0.
A typical level would be 5.00 for a reasonable warning level.

As for giving permissions to users in another group to turn the site on and off, there is no function to do this. You would probably have to write a modification to do this.