It was with the coming of OS X Yosemite when users could finally try their hands at automatically installing updates for Mac OS X. In the past, Apple has offered options to download updates in the background, and install important security updates and app updates, however the new options in Yosemite allow encompassing all software updates.
Much the same as manual updates, if the automatic updates go wrong, they can result in your Mac going dark. So it's recommended that you must enable Time Machine backups on your Mac before enabling auto updates for OS X Yosemite.
Every time there's a new update, the Internet is shelled by “this bricked my PC” crowd. The vast majorities of these people configure their machines in unusual ways and install faulty software. So alongside enabling regular backups, make sure you aren't making those weird mistakes.
How to Enable or Disable Mac OS X Auto Updates in El Capitan or Yosemite
Step #1. From the Apple menu, click System Preferences.
Step #4. Check all the boxes, including the ones to “Automatically check for updates” and “Download newly available updates in the background.”
Watch out how to enable or disable Mac OS X auto update:
Keep in mind; the new options are not the same as what was being offered by Apple in the prior versions of OS X. In this way, if an update to Yosemite (for example, OS X 10.10.1) is available, the new settings will automatically download and apply it.
Remember, all doesn’t prefer the automatic update processes. For example, if you use your Mac consistently, you'll get notifications for any available updates and eventually you'll be able to manage them at your convenience.
In case you don't automatic updates, simply uncheck “Install OS X Updates” box.