Now, in 2012, I still use this very useful approach to backup a list of installed packages.
UPDATE. There is one important difference: it is only possible to carry out the commands as superuser.
Originally Posted by Cynical
So open a terminal and give in the following command:
By doing so, you will get list of installed packages in the HOME directory, with the name "installed-software". Backup this file to an external hard disk, to another computer, etc. It is this file you neeed to use at another computer or at the same one after a fresh install of the same distro and version.
sudo dpkg --get-selections > installed-software
After the fresh install, copy the file "installed-software" to the HOME directory of the new configuration. A next step is the installation of the package "dselect": that one will not be installed by default along with a fresh install. For this purpose, open a terminal and give in the following:
For getting your favourite software after the fresh install, also use a terminal, with the following command:
sudo apt-get install dselect
sudo dpkg --set-selections < installed-software
As I said before, you can do so with a view to installing the same packages after a fresh install of the same distro and version: either at the same computer or at another one. !!! If you want to create a similar configuration after an upgrade, act as follows:
than carry out the instructions summarised here.
Why: during each upgrade, several packages will be obsolete, added, removed, etc.