I think there is a dia package to do diagrams DFD included, but can not generate the code or scripts to implement in a database, at least 2 years ago when I used it. Take a look.
You can get a graphical package management as yumex, and search for available packages containing DFD word in their description.
Pietro Pesci Feltri
PowerBook 15" G4 and
MacBook Pro 17" Intel Core 2 Duo
Intel I5 Desktop