Here’s a simple tutorial on how to backup a list of all your installed repository applications, and restore them to another machine, perhaps even the same machine after a clean installation. This can save you an incredible amount of time, especially when this task must be repeated often. Of course, being that Ubuntu is based on Debian, this will work for any Debian based platform.
First, from a computer with all the applications preinstalled, retrieve your installed package list and redirect the output to a file called packages.txt. Save this package list somewhere so that you can use it for the restore process.
sudo dpkg --get-selections > packages.txt
To restore all the applications from your list, you must follow a three step process very carefully.
sudo dpkg --clear-selections sudo dpkg --set-selections < packages.txt sudo aptitude install
You will be prompted to install all the new applications in the list.
Another example of what this process allows you to do is create a baseline of all the applications after a clean installation of Ubuntu. Let’s say you would like to remove any applications installed since the clean install, perform the exact same process, and any package not defined in that list will be removed.
sudo dpkg --get-selections > clean-install-package-list.txt sudo dpkg --clear-selections sudo dpkg --set-selections < clean-install-package-list.txt sudo aptitude install
The very first command of “–clear-selections” marks all currently installed packages to the state “deinstall”. When you restore the list of applications using “–set-selections”, only packages ommited from the list will remain in the “deinstall” state. Aptitude will honor the deinstall state and remove the extra packages, leaving you only with packages from the list. Most excellent.