Hopefully I can help someone with this tip:

If you want to update your computer installation, move harddrives around, or whatever, and you want your linux experience to be the same as the machine you are currently using, then follow this:

To migrate a computer from one Debian-based linux to another you need to use this:

Open terminal.

do:

dpkg -l | awk '{print $2}' > packages.txt

cat packages.txt

Now you have a list of packages installed, you can save this wherever you like, to be transferred to new pc.

To bring a new system up to the same packages installed:

terminal (on new system, with packages.txt in same directory):

sudo apt-get install `cat packages.txt`

NOTE: the Apostrophe in the apt-get install routine, rather than single quote.