Installing OS X has never been easier than it got in Yosemite, when the installers were moved to the App Store. And since then it’s just gotten easier, and easier. In this article, we’ll upgrade a Mac from OS X 10.11 (El Capitan) to macOS Sierra (10.12), the latest and greatest. The first thing you should do is clone your system (especially if you’re upgrading a server). The second thing you should do is make sure you have a good backup. The third thing you should do is make sure you can swap back to the clone should you need to do so and that your data will remain functional on the backup. The fourth thing you should do is test that clone again…
Once you’re sure that you have a fallback plan, let’s get started by downloading “Install macOS Sierra” from the App Store. Once downloaded, you’ll see Install macOS Sierra sitting in LaunchPad, as well as in the /Applications folder.
Open the app and click Continue (provided of course that you are ready to restart the computer and install Sierra).
At the licensing agreement, click Agree (or don’t and there will be no Sierra for you).
At the pop-up click Agree again, unless you’ve changed your mind about the license agreement in the past couple of seconds (I’m sure it happens).
At the Install screen, click Install and the computer will reboot.
And you’re done. Now for the fun stuff!
