Alternatively you can use Aptik to do this task using a GUI instead a CLI (personally I prefer the CLI method described above, but here you have another possible solution). Aptik allows you to Backup & Restore your favourite App's, PPA's and many more!
You can get Aptik from official PPA using this simple line:
sudo apt-add-repository -y ppa:teejee2008/ppa && sudo apt-get update && sudo apt-get install aptik
sudo apt-add-repository -y ppa:teejee2008/ppa
sudo apt-get update
sudo apt-get install aptik
Here you have more info about Aptik:
I used several times in university computers (I'm the SysAdmin) after a fresh Ubuntu installation and this tool help me to save a lot of time.
Also I recommend you Timeshift to make an OS image backup from same author (Clonezilla randomly failed when restoring an HDD image disk into a SSD and really), but also I recommend you Ubuntu AfterInstall wich you can to install a lot of useful software (restricted extras, VLC, etc...) using only a few mouse clicks.