# backup the sources.list file !
# backup
apt-mark showmanual > .installed_ubuntu_packages
# on another system
# restore sources.list file !
xargs < .installed_ubuntu_packages apt-get install -y


ä old school way
# backup the sources.list file !
dpkg --get-selections > .installed_ubuntu_packages
# on a new system
# restore sources.list file !
dpkg --clear-selections
sudo dpkg --set-selections < list.txt