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I do get the following error message(s) when running apt-get update:

Err precise-backports/multiverse i386 Packages
503 Service Unavailable

The server is not behing a proxy, but there is a firewall, I suspect that the firewall is causing me troubles (transparant proxy?).

What kind of checks can I perform to be sure it is the firewall and not something else? Which specific ports should I check in which way to get conclusive evidence?

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Navigate to your "Software Sources" ( I do not know which "buntu" you are using). Try a different server either in your country or in a nearby country. It works for me, when I occasionally get this problem.

Good Luck


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