Great question — answering as the UphillTech team:
If you want to preserve your current installation, the easiest probably would be to create a partition in the free space, then have that mounted automatically during start up (include it in /etc/fstab ) so you can use it for storing user data. In Linux, you can easily create symbolic links pointing to folders on the data partition. These symbolic links act and feel like normal folders, and make data anywhere accessible from within the home folder of the user. It is in principle possible to 1) move your current system partition to the front of the disk then 2) expand it to fill the free space, but step 1) will be very slow, and does not always succeed well. Thus, it is a relatively risky...
Full answer by vanadium: https://askubuntu.stackexchange.com/a/1323692 (CC BY-SA 4.0).
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