Ask Ubuntu have a helpful article on how to backup your settings and installation applications on a Linux distro. I’ll have to give this a go with a VM and see if it works for my transition from Pop OS to Pop OS LTS.

A quick way of backing up a list of programs is to run this:

dpkg --get-selections > ~/Package.list
sudo cp -R /etc/apt/sources.list* ~/
sudo apt-key exportall > ~/Repo.keys

It will back them up in a format that dpkg can read^* for after your reinstall, like this:

sudo apt-key add ~/Repo.keys
sudo cp -R ~/sources.list* /etc/apt/
sudo apt-get update
sudo apt-get install dselect
sudo dselect update
sudo dpkg --set-selections < ~/Package.list
sudo apt-get dselect-upgrade -y

You may have to update dpkg’s list of available packages or it will just ignore your selections (see this debian bug for more info). You should do this before sudo dpkg --set-selections < ~/Package.list, like this:

apt-cache dumpavail > ~/temp_avail
sudo dpkg --merge-avail ~/temp_avail
rm ~/temp_avail

Settings and Personal Data

Before you reinstall, you should probably back up the settings from some of your programs, this can easily be done by grabbing folders from /etc and all the content from your user directory (not just the stuff you can see in nautilus!):

rsync --progress /home/`whoami` /path/to/user/profile/backup/here

After you reinstall, you can restore it with:

rsync --progress /path/to/user/profile/backup/here /home/`whoami`

So all together as a pseudo-bash script.

This assumes there is only one user on the machine (remove /'whoami' otherwise) and that you used the same username on both installs (modify dest. of rsync otherwise).

dpkg --get-selections > ~/Package.list
sudo cp -R /etc/apt/sources.list* ~/
sudo apt-key exportall > ~/Repo.keys
rsync --progress /home/`whoami` /path/to/user/profile/backup/here

##  Reinstall now

rsync --progress /path/to/user/profile/backup/here /home/`whoami`
sudo apt-key add ~/Repo.keys
sudo cp -R ~/sources.list* /etc/apt/
sudo apt-get update
sudo apt-get install dselect
sudo dpkg --set-selections < ~/Package.list
sudo dselect

Thanks to AskUbuntu.com Question 9135 – How to Backup Settings and list of installed packages.