[Samba] Renaming user in Samba 3

[Mi]

Hello,

I need to rename a few users: change their login, but leave everything else 
as is, like their password, etc.

On the Linux side usermod seems to have done what I wanted:

   usermod -l $newname -c $newfullname -d /home/$newname -m $oldname

For Samba, I cannot find any command or option to pdbedit that would do that.
Before, I could have edited smbpasswd by hand, but now it seems everything 
is in /var/lib/samba/passdb.tdb.

I am using "smbd version 3.0.2a-Debian", and my smb.conf has

   passdb backend = tdbsam


Thanks for any help,

Mi