Final answer:
To prevent upgrades from altering customized system behavior, it is essential to back up your system, segregate customizations, tweak update settings for manual approval, utilize a testing server, and employ version control systems.
Step-by-step explanation:
Preventing Unwanted Upgrades from Altering Customized System Behavior
Customizing your system and then having an upgrade overwrite those customizations can be frustrating. To minimize this risk, it's important to take a few proactive steps. Firstly, always backup your system before performing upgrades; this gives you a restore point should anything go awry. Secondly, divide your customizations into those that change system files and those that are user-specific. If possible, make user-specific changes that won't be affected by system updates.
To further protect against unwanted changes, configure your system’s update settings to prompt you before installing updates. This way, you can review what the upgrade entails. For high-risk environments, you might choose to have a testing server where you can trial the upgrade before deploying it to your primary system. Lastly, deploy the use of version control systems for your configurations. Software like Git allows you to track changes and revert to previous versions if necessary.