You might need to reinstall a fresh copy of Ubuntu due to many reasons, but guess whats the most hectic thing after a fresh operating system reinstall? It is to install all of the software packages again. Let me share an easy way to install these packages again quickly, in case you need to fresh install Ubuntu.
Synaptic Package Manager is the main source of all types of installations in Ubuntu, so before you reinstall Ubuntu make sure to make a backup of all the currently installed software via Synaptic Package Manager. Launch Synaptic Package Manager from System > Adminsitration > Synaptic Package Manager. Once it is launched, backup your currently installed software into some external drive USB etc. For this purpose go to File > Save Markings.
Now type a name for this backup and select the location where you want to save it(USB is recommended) and then click Save.
The backup will be saved in your USB disk, now perform the fresh installation of your Operating system and restore all of the installed packages from File > Read Markings option of the Synaptic Package Manager.
Finally browse and locate the backup file which you generated earlier.
Click Open and Ubuntu will install all of the previous packages again, thus saving lots of headache and time. Enjoy!