In my need to back up debs from my installed system (trying to fix Brostrend's idiotic mistake) I found a very useful tool!
For years I would just backup /var/cache/apt/archives to my storage drive, and call it a day.
This doesn't work anymore for Ubuntu because not all the debs that are installed are in that folder anymore.
Using the great info I found at AskUbuntu, i first used apt-get to install dpkg-repack, then made a folder on my boot drive named repack, changed directory to that folder, and then I ran the command dpkg-repack `dpkg --get-selections | grep install | cut -f1`.
In just a few minutes I had a folder named repack with every single deb package i had installed in the folder.
For me this is very very useful.
According to the AskUbuntu article, sudo dpkg -i *.deb launched from inside the repack folder will re-install every debian package in that folder.
I haven't personally tried this yet, but when I do, if this goes other than planned, I will update this article.
I'm not 100% certain whether it handles all my dependencies yet, but I will let you know once I have confirmation.
-Denny