[ubuntu] How can I do a fresh install and get all my old packages?

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http://ubuntuforums.org – I'm running Ubuntu 11.10. I want to install 12.04 (LTS), which I'll probably stick with for the next few years. I'll be using the same /home partition for both versions. Every time I have tried to upgrade a Ubuntu distro in the past it has failed in one way or another, so this time I want to do a fresh install on a spare partition, so that if there are any problems I can still boot my 11.10 version. What I want to know is this: is there a way for me to get 12.04 automatically to install the appropriate versions of all additional software I have previously installed in 11.10? I thought (Hardware)