With this suggestion, I'm assuming your old installation will still boot!

To replicate one set of packages on another machine:

On System A, run:

dpkg --get-selections | grep -v deinstall > my-selections

Move the my-selections file over to System B.

On System B, run:

dpkg --set-selections < my-selections

and then:

sudo apt-get dselect-upgrade

Important note: if you have installed packages from non-standard repositories and/or PPAs, you will also want to copy /etc/apt/sources.list and the contents of /etc/apt/sources.list.d/ from System A to System B before you run the upgrade.

You can use dpkg to see what you've removed as well (NB: this will also include packages that you manually installed and removed):

dpkg --get-selections | grep deinstall

You can see your results in the terminal, or, of course, redirect to a file.

This thread from superuser.com gives this solution:

aptitude search '?installed ?not(?automatic)'

If your apt logs are in /var/log/apt, something like this should work:

gunzip -c /var/log/apt/history.log.*.gz | grep "apt-get install"

Or if you want to get rid of some of the repetitive junk in the output:

gunzip -c /var/log/apt/history.log.*.gz | grep "apt-get install" \
  | cut -f4- -d" " | sort | uniq

You could use apt-mark, but I recommend debfoster:

sudo apt-get install debfoster
sudo debfoster

This will inspect all installed packages and figure out which ones are keeping the others installed:

texlive-full is keeping the following 161 packages installed:
  cm-super cm-super-minimal context doc-base dvipng feynmf
  fonts-gfs-artemisia fonts-gfs-baskerville fonts-gfs-bodoni-classic
  ...
Keep texlive-full? [Ynpsiuqx?], [H]elp:

As you answer "y" to each question (just push Enter to move quickly), debfoster will collect the package list and write them line-by-line to a file. By default this is at /var/lib/debfoster/keepers. It looks like this:

gnome-do
texlive-full
...

I configure debfoster via /etc/debfoster.conf to put this list at /etc/debfoster-keepers and track the file with etckeeper to keep history and backups. The answer here shows how to install a list of packages from a newline-delimited text file:

sudo apt-mark manual $(cat debfoster-keepers)

Note a limitation here, packages you purged have a '-' in front of them. So you want to remove those lines before calling apt-mark.

Even though the debfoster's website says that debfoster is deprecated in favor of aptitude, I prefer debfoster's prompt and simple configuration. It puts you in the middle of your package database and lets you clean things up, making the auto and manual packages more obvious.

Type "h" at the debfoster prompt to explain your options. Type "?" to see the package description. The how-to here might be useful.

comm -23 <(apt-mark showmanual | sort -u) <(gzip -dc /var/log/installer/initial-status.gz | sed -n 's/^Package: //p' | sort -u)

Gives all manually installed packages (not system packages, not dependencies). For examples it shows build-essential but not gcc.

For those who prefer using apt-* tools, there's an apt-mark utility that allows both querying and modifying manual/auto state.

apt-mark showmanual

You can also specify pattern for packages you interested in:

apt-mark showmanual qemu\*

I finally got it now:

outfile="$(mktemp)"
pattern='(\[INSTALLIEREN\]|\[INSTALL\])'

if [[ -f "/var/log/aptitude.1.gz" ]]
then
        gunzip -c /var/log/aptitude.*.gz | grep -E "$pattern" | awk '{ print $2; }' > "$outfile"
fi

if [[ -f "/var/log/aptitude" ]]
then
        grep -E "$pattern" "/var/log/aptitude" | awk '{ print $2; }' >> "$outfile"
fi

sort "$outfile"
rm "$outfile"

I'm able to pull everything by opening the log files in /var/log/apt/

I then go in and manually filter out the apt-get install packages. There may be a way to do this programatically but I'm not aware of it.

cd /var/log/apt
cat  history.log | grep Commandline

this way you see the list of commands performed in the past.

Remove the grep code if you need more information:

less history.log

if the log is compressed (i.e. end with gz)

gunzip <filename>

to zip it again when finished you can do:

gzip <filename>

I didn't see any solutions here work for me, I have installed quite a few deb packages with dpkg and a few of the items I was particularly looking for were missing.

A rather lengthy one liner, but convenient to copy and paste would be:

export DPKG_INITIAL=$(mktemp) DPKG_INSTALLED=$(mktemp) DPKG_CUSTOM=$(mktemp) DPKG_DEPS=$(mktemp) zgrep -E '^Package' /var/log/installer/initial-status.gz | awk '{ print $2 }' > $DPKG_INITIAL ; awk '$3 !~ /install|remove|purge/ { next } { gsub(/remove|purge/, "uninstall", $3) ; gsub(/:.+/, "", $4) ; a[$4]=$3 } END { for (p in a) { if (a[p] == "install") { print p } } }' /var/log/dpkg.log | sort -u > $DPKG_INSTALLED ; comm -23 installed initial > $DPKG_CUSTOM ; function rdep() { apt-cache rdepends $1 | tail -n +3 | sed -e 's/^ //' -e '/^ /d' | cut -d':' -f1 | sort -u; } ; echo "$(for i in $(cat custom) ; do rdep $i ; done)" | sort -u > $DPKG_DEPS ; comm -23 custom deps > my-packages ; rm $DPKG_INITIAL $DPKG_INSTALLED $DPKG_CUSTOM $DPKG_DEPS

The above command saves a list of packages to a file in your current working directory named my-packages.

Explanation

I first built a list of packages that composed the baseline of packages selected during installation.

zgrep -E '^Package' /var/log/installer/initial-status.gz | awk '{ print $2 }' > initial

Followed by a long list of items installed in general.

awk '$3 !~ /install|remove|purge/ { next } { gsub(/remove|purge/, "uninstall", $3) ; gsub(/:.+/, "", $4) ; a[$4]=$3 } END { for (p in a) { if (a[p] == "install") { print p } } }' /var/log/dpkg.log | sort -u > installed

I then compared the two files initial and installed to list only the items unique to installed.

comm -23 installed initial > custom

From there I wanted to filter out the dependencies, this is where this method may miss some desired packages, it is unaware of dependencies that are also explicitly installed.

I wrote a quick bash function to shorten this steps in processing these items.

function rdep() { apt-cache rdepends $1 | tail -n +3 | sed -e 's/^ //' -e '/^ /d' | cut -d':' -f1 | sort -u; }

After that I passed each line from my file custom into this function with xargs.

echo "$(for i in $(cat custom) ; do rdep $i ; done)" | sort -u > deps

Once I had the long list of every possible dependency, (not sure on the every possible statement), I once again got the lines that were unique to a single file.

comm -23 custom deps > manual

And my finished list of packages is now in a file named manual available for me to review.