Generating a list of installed packages in Ubuntu

I hacked myself a solution :)

dpkg --get-selections | cut -f 1 > /tmp/all
apt-mark showauto > /tmp/auto
diff /tmp/all /tmp/auto | grep '<' | sed 's/.* //'

That will first generate a complete list "all" of installed packages, then a list "auto" of automatically installed ones, and finally create a list of differences from all and auto, which is the list I need.

Any better suggestions?

You could filter out the lib packages and manually filter the remaining ones. I don't think that there's a standard way to do this.

dpkg --get-selections |wc -l
1831
dpkg --get-selections |grep -v ^lib | wc -l
1060

# ASSUMING your dpkg Logs go back to the initial machine install

###(May/Probablly NOT work across dist-upgrades)

apt-mark showauto >/tmp/auto.pkgs

cp /dev/null /tmp/dpkg.full
for LOG in $(ls -rt /var/log/dpkg.log.[0-9].gz  /var/log/dpkg.log.1[0-9].gz)
do
    test -e $LOG && gunzip -c  $LOG>> /tmp/dpkg.full
done
for LOG in $(ls -rt /var/log/dpkg.log /var/log/dpkg.log.[0-9]  /var/log/dpkg.log.1[0-9]) 
do
    test -e $LOG && cat $LOG >>/tmp/dpkg.full
done

awk -v initialinstall=1 '
   / install grub-pc / {initialinstall = 0; next;}                     
   / install / {if ( initialinstall == 0) print $4;}
' /tmp/dpkg.full | grep -vf /tmp/auto.pkgs >~/iInstalled.pkgs

If you want a list of packages that are not marked as automatically installed (which is not always the same as not being a dependency), you can do this in a simpler way using aptitude like so:

aptitude search ~i | grep "^i   " | awk '{ print $2 }'

If you are really concerned with weeding out all dependencies, you can look into the ~R and ~D search patterns. I think aptitude is the currently recommended front-end to dpkg and apt. You will find that it has a number of really useful command-line options, in addition to the ncurses interface.