I'm a Linux only user so AT&T's DSL has been a challenge. I have found a workaround for some things at least. If you have Linux with KDE installed, you can use Konqueror to at least reset passwords and such. My password has a habit of getting messed up somehow and I have to reset it. This is how this worked for me at least. Open Konqueror, type in google.com and hit return. It will take you to the error page that AT&T has telling you the password is not matching up. You should get that page no matter what URL you type in. Once that page comes up, go to Tools, then go down to Change Browser Identification and slide over to Other then select Safari 2.0 Mac OS X. Once you have that selected, just click the continue button to reset your password. This may work for installing for the first time as well but I have not tested that. Maybe someone could test this and report what happens. I did have a AT&T tech call me a while back. They are talking about having some small amount of support for Linux. I just hope this will help in the meantime. It's sort of hard when you don't have any windoze boxes in the house.
I found this link somewhere on the net. It may help someone one day. https://attreg.att.net/dsltech I haven't used it but it does talk to you when you go there. lol The claim is you can use this even if you don't have the CD and set up your DSL connection, user name and password and such. Hope this helps someone.
I recently performed the setup on Ubuntu GNU/Linux using Firefox. Before visiting https://attreg.att.net/dsltech you need to setup your modem to connect using the username email@example.com and the password attreg. If you have trouble, call tech support. They where able to guide me through the setup, even without a supported system. They really should include the generic instructions in the kit. It would make things simpler for us and them.