I'm trying to make the Update Manager work through the proxy on my ubuntu 9.10. I've tried what was suggested in this question, but the Update Manager still reports 409 conflict. Would really appreciate if anybody could help me with this.
The window manager solution turned out to simple: System->Administration->Synaptic package manager, then in the Synaptic window Settings->Preferences->Network. Manually enter the http_proxy field. And it works now. Still am curious as to how to do this from command line though.