configuration:
linux server: mandrake 10.0
eth0: internet
eth1: LAN

2 windoze pc's

how to configure internet sharing with the webmin tool ?
same for file sharing (configuring samba with webmin tool).

Sharing a Internet connection requires several distinct systems, although several OSes provide a ready made configuration that you can activate without knowing the details. IIRC, Mandrake 9 had a wizard to do this, although it didn't work for me.

At minimum you need:

- Valid networking settings on each machine (or use DHCP to automatically assign settings to the clients).
- Routing enabled on the gateway machine.

Routing can be handled by the Shorewall firewall, which Webmin provide an interface for. I don't know about Mandrake 10, but 9 used Shorewall as the default firewall. Shorewall is designed for gateway systems, so it enables routing automatically when it's switched on.

It is also useful to have:

- A DNS server (Webmin can manage BIND), although your machines could just use your ISP's DNS until you get it working.
- Squid proxy server, which makes Web access lightning quick. Again, your machines could just use your ISP's proxy, but Squid is well worth the time to set up.

For Samba I would recommend installing the samba-swat package, which is very easy. Once installed you can get to it's interface by typing this in a Web browser on the machine:

http://localhost:901

Samba has a zillion options, and the regular Webmin interface doesn't make it easy to spot the small number you actually need to set. Webmin is compatible with SWAT so you can switch later on.

I tried in an earlier attempt with SWAT
in fact I'm strugling with this problem for 5 long days already,
it's horrible, I can't do my work because of this ...

eventually I reinstalled mandrake 10 and webmin.

The thing I need is masqing (I think)
I was reading that configuring my linux as dhcp server
will conflict when I make it a webserver (and that's the idea).

I know already a bit my way in webmin,
but in the networking configuration tool (rouding and gateways)
I just don't know which parameters to fill in for internet sharing.

Same for Samba.

You're right that IP masquarading needs to be enabled as part of the routing. Shorewall does this automatically. Having done routing and firewalling by hand in Linux, I'm happy to use and recommend Shorewall to take care of the details for small networks. If you use the Routing and Gateways module to manually configure the routing you also need to use the Linux Firewall module to set up firewalling as well. The only reason I can think of for doing all this on a small network is for the experience, in which case you should use the command-line to get a better feel for how things work.

As regards DHCP, I think that the advice you read relates to DHCP clients. A machine whose IP is assigned randomly assigned by a DHCP server cannot be accessed by DNS name, because when the IP changes the DNS record will become invalid. The solutions are either to pay your ISP a premium for a fixed IP address for your connection, or use a third-party service like No-IP or dyndns.org, which automatically update DNS whenever the machine's IP address changes.

If the Linux box is the server, and the two Windows machines are the only other things on the network then don't bother with a DHCP server. You can put in the necessary settings on the Windows machines in 1/10 of the time it would take to configure your DHCP server.

With Samba, bear in mind that it's the most complex part of your network and won't work for you unless the IP and DNS configurations are completely right, which includes making sure that the firewall configuration allows traffic on all of the ports that SMB uses. If you're still at the stage of DHCP and routing then I recommend that you don't look at Samba until the network infrastructure is done, or you could drive yourself mad trying to figure out why it isn't working...

The most fool-proof method of moving files between Linux and Windows is SSH - the Linux box will already have the SSH server running, SSH only requires IP addresses and port 22 access on the Linux box, and the WinSCP graphical client for Windows takes two minutes to install with the usual wizard. You can then work on Samba at your leisure once you are happy with the other networking systems.