Here is a one-liner to list all packages manually installed since the fresh installation of my Ubuntu laptop:
$ comm -23 <(apt-mark showmanual | sort -u) <(gzip -dc /var/log/installer/initial-status.gz | sed -n 's/^Package: //p' | sort -u) ansible ansible-doc apache2 audacity avidemux ... vim virtualbox-4.3 vlc vpnc whois $ |