Restore All Installed packages in Ubuntu Hardy Heron and to a New machine

The following command creates a list of all the installed packages at the present time:

sudo dpkg --get-selections > /etc/package.selections

Now
we created our package list and we can copy this list to a new ubuntu
computer and install the same packages in the list to the new machine
or, restore the packages to the time you created the package list:

sudo dpkg --set-selections < /etc/package.selections && apt-get dselect-upgrade

The above command will uninstall all packages installed after you created your restore list.