I’ve finally gotten round to setting up the VDS Mythic-Beasts have kindly donated to host the API backend for one of my open-source projects. A few nights ago I enabled IPv6 and today when I went to run apt-get update it just hung saying:

0% [Connecting to gb.archive.ubuntu.com (2a01:450:10:1::10)]

As they had previously worked, I suspect it’s IPv6 problem, quick google and…

http://askubuntu.com/questions/272796/connecting-to-archive-ubuntu-com-takes-too-long

For sites which prefer IPv4 connections change the last line to

precedence ::ffff:0:0/96 100

Bingo.