I came across a situation I’d never encountered before earlier so I thought I’d do a quick post in case someone else is momentarily stumped too.

During a netinst of Debian you are asked to pick a mirror server. The netinst CD is very small so the majority of packages are downloaded over the network.

What happens when you’re in a firewalled environment, and your server cannot speak to ftp.uk.debian.org, or whichever server you normally use, directly?

In this case we have an Approx server which acts as our caching proxy for Debian packages for the whole network.

But how to use our Approx server instead of ftp.uk.debian.org?

What I hadn’t noticed in the installer dialog was, waaaay at the top of the long list of mirror locations, you have the option of adding your own.

So for the mirror specify:

Don’t forget the 9999 non-standard port number Approx uses.

So simple.