In order to install MacOS Sierra, you first need to make sure your Mac supports it. MacOS Sierra requires one of the following Mac models and versions of OS X. It also requires at least 2GB of memory and 8.8GB of storage space.
- iMac (Late 2009 or newer)
- MacBook (Late 2009 or newer)
- MacBook Pro (Mid 2010 or newer)
- MacBook Air (Late 2010 or newer)
- Mac mini (Mid 2010 or newer)
- Mac Pro (Mid 2010 or newer)
- OS X El Capitan v10.11
- OS X Yosemite v10.10
- OS X Mavericks v10.9
- OS X Mountain Lion v10.8
- OS X Lion v10.7
You can simply Get Sierra from the Mac App Store
Before upgrading, it’s a good idea to back up your Mac. Then follow these steps:
- Open the App Store app on your Mac.
- Search the App Store for macOS Sierra, or go directly to the macOS Sierra page.
- Click the Download button on the macOS Sierra page. A file named Install macOS Sierra downloads to your Applications folder.
- After the download is complete, Install macOS Sierra opens automatically. (You can also open it from the Applications folder, Launchpad, or Spotlight.) Click Continue and follow the onscreen instructions.
How to do a clean install of MacOS Sierra
First, you need to create a Bootable Installer. To do this you have two options, you can use the Terminal or you can use software made for this. In both cases, you need a USB thumb drive to store the install file.
Download the macOS Sierra installation package from the Mac App Store. Once it has downloaded, follow these steps to create a USB bootable installer.
- Install Disk Creator is a straightforward way to create a boot disk. I was able to make a macOS Sierra external USB boot disk in a few minutes, and the installation worked without a hitch. Also, works with older versions of OS X.
- Diskmaker X is a popular app. It also supports older versions of OS X.
- Open Disk Utility (found in the Applications/Utilities folder), select the thumb drive in the sidebar and click the “Erase” button.
- Name the USB drive “Untitled” if it isn’t already, choose the Format “OS X Extended (Journaled)”, and click “Erase”. Once your thumb drive is formatted and the macOS installation package has finished downloading, open up Terminal (found in Applications/Utilities).
- Now, ensure the USB drive is the only disk named “Untitled” connected to your Mac, and then paste the following command into the Terminal window, and press Enter: sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia –volume /Volumes/Untitled –applicationpath /Applications/Install\ macOS\ Sierra.app –nointeraction
- You should be prompted for your administrator password. Enter it, and the command will create a bootable Sierra installer on the USB drive. The process will take a few minutes to complete, so leave it running.
The installation of MacOS after restart:
Once the USB installer has been created using one of the methods above, restart your Mac and hold down the Option key (alt) as soon as you hear the reboot tone. Then follow these steps to complete:
- Use the mouse pointer or the arrow keys on your keyboard to select the disk called “Install macOS Sierra” in the drive list that appears on the screen.
- Once the USB drive has booted, select “Disk Utility” from the Utilities window, choose your Mac’s startup drive from the list, and click “Erase“.
- When your Mac’s startup disk is formatted, return to the Utilities window and select “Install macOS“, choose your freshly erased startup drive when asked where to install the OS, and follow the onscreen prompts to complete the installation.
After the installation of MacOS
Once the clean installation of macOS Sierra is up and running on your Mac, you can either restore your data from a Time Machine backup using Migration Assistant (found in Applications/Utilities), or begin restoring your apps, files, and settings manually to get your Mac set up just the way you like it.