Ubuntu: software backup and reinstall

Recovery
A quick way of backing up a list of programs is to run this:
dpkg --get-selections > ~/Package.list
sudo cp /etc/apt/sources.list ~/sources.list
sudo apt-key exportall > ~/Repo.keys

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It will back them up in a format that dpkg can read for after your reinstall, like this:
sudo apt-key add ~/Repo.keys
sudo cp ~/sources.list /etc/apt/sources.list
sudo apt-get update
sudo apt-get install dselect
sudo dpkg --set-selections < ~/Package.list
sudo apt-get dselect-upgrade -y