When using Update Manger on a *nix machine, you may encounter connectivity issues with reaching SDC or any other internal server if you have an NTLM proxy setup in your environment. This is related to some specific behavior of the NTLM proxy on *nix machines. To resolve this problem, you have to set the following two variables in the same session that you are running Update Manager:

This results in the OS being explicitly notified for using an NTLM proxy and should resolve the connectivity problem.