dynamic DNS for shell account users

 userv-dyndns is a userv service which allows non-root users to
 modify individual DNS records in specified zones in a controlled way.
 .
 Typically, this can be used to provide a `dyndns.org'-like service
 which is modifiable by shell account users.
 .
 The default configuration creates the infrastructure (including a
 service user) but does not allow any users to modify the DNS.