To record a demo you need to be admin, so - even on a locally run server - you will need to set a master-password and authenticate yourself with this to gain admin status.
If you're running a linux-machine you could start a (private (=non-public)) server something like this
bin_unix/linux_server -mlocalhost -pMY_SECRET_PASSWORD
and then in your client execute
/setmaster MY_SECRET_PASSWORD

It is not possible to do this on the mini-server running for your regular client, you will need to run a dedicated server and then connect localhost to it!

This page is just a stub - please feel free to elaborate more on this subject :-)