I'm planning to reinstall my OS by not formatting my root partition (I only use a single partition) as this will preserve the contents of my home directory, but the problem is that when I've done it in the past, it's wiped all my third party applications, and I was wondering if there was a way I could back up and restore them afterwards.
You can do this in the synaptic package manager (System->Administration) Make sure your selection is in the "All" section then go to File->Save markings, make sure you check mark "Save full state, not only changes" then save (somewhere where it won't be formatted ;)
When you are done installing you can go to File->Read markings
Most of your programs will download, except the ones which you added a repository for (well at least until you re-enter them). You might have to fix some of the broken packages in synaptic after as well.
I'm sure someone else might now how to backup and restore the sources list..
A lot depends what kind of installing methods 3rd party software is offering.
To help out re-install of those 3rd party software you should
Take copy of apt-get repositories (
/etc/apt/sources.list) for 3rd party repositories. Example spotify and virtualbox provides repositories for installation.
Copy all .deb's and zip's/tar.gz packages on your hard-drive (I usually find them from my home folder either Downloads or Software, could be something else on you). But usually benefit of this depend how fast connection you have and wether or not that version uses deprecated functionalities no longer provided by new version.
Crawl down your applications menu and write up all 3rd party software you want still to find from your new system and write that down to paper.
I understand that OneConf is tool which one of goals will be to make this easier. Might be worth keep and eye on development.
as i read, stipple is the best solution while oneconf is final:
"Save a list of installed applications, .config files, and other settings to a couchDB. Sync this DB to other computers with Ubuntu One. This application also helps you install those packages and .config files on your other computers."