Just in case something goes wrong, make sure to back up your Mac Computer before committing to an OS update as Apple releases Big Sur in the near future.
1. Move your data to a new drive
2. Create a ghost user account in the internal hard drive
3. Create a copy of the home directory on the external drive.
Check out an in-depth Home Directory episode on Big Sur preparation by watching the latest Hands-on Mac, hosted by Leo! Twit.tv/hom30