Sharing Option config file?

[zz_fish]

Hi there, I have a question on samba configuration.

In the past I used to change samba config by editing /etc/samba/smb.conf

Recent I discovered this GUI way of doing it, by right clicking a folder and click File Sharing, this has made life a lot easier.

The problem is, this operation does not seem to modify smb.conf, and I cannot find where it saves the samba configuration. Now I want to do some changes beyond the GUI limitation (like adding force user option), where do I find the config file?

The system is Ubuntu 8.04 if it matters.

Thanks in advance.