1. Backup your system. Typically I create a snapshot. 2. Update existing packages and reboot the Debian 9.x system. 3. Edit the file /etc/apt/sources.list using a text editor and replace each instance of stretch with buster. 4. Update the packages index on Debian Linux, run: sudo apt update 5. Prepare for the operating system upgrade, run: sudo apt upgrade 6. Finally, update Debian 9 to Debian 10 buster by running: sudo apt full-upgrade 7. Reboot the Linux system so that you can boot into Debian 10 Buster 8. Verify that everything is working correctly.