I am developing an application with different behavior depending on the arguments :

• "-config" starts a Gtk window to change options, start and close the daemon.
• "-daemon" starts a background process that does something every X minutes.

I already know how to use fork/system/exec etc...

But I would like to know the main logic of such application to :

• restart or refresh the daemon when configuration change.
• keep only one instance of the daemon.

I have read that killing the daemon to restart it is not a clean way to do.
How other applications do ? (ubuntuone, weather forecast, rss feed working with notification area)

Thanks for your help.

PS : I don't want to create a system-wide daemon, just a user application with a background process.