I don't think I found a plugin doing this.
The idea would be that RC would read the information in /etc/passwd to fill the Name and Surname fields of a newly created RC user.
Right now I'll have to login to each new user and input these fields for them.
Is there a way to do this ? Or maybe even a RC user creation script I could (carefully ;-)) edit ?
have a look at the new_user_identity identity plugin which ships with roundcube. it uses LDAP to get the user information but it should give you a starting point to create a plugin which uses /etc/passwd