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Can I download a previous macOS?
Any old macOS you have won’t run anymore, because the security certificates on them expired then. However, any old macOS installer that you can download from Apple now will work. For some years, Apple kept the old installers for versions such as El Capitan, Sierra and High Sierra in the App Store, but hid them.
How do I install an older version of macOS?
Here are the steps Apple describes:
- Start up your Mac pressing Shift-Option/Alt-Command-R.
- Once you see the macOS Utilities screen choose the Reinstall macOS option.
- Click Continue and follow the on-screen instructions.
- Select your startup disk and click Install.
- Your Mac will restart once the installation is complete.
How do I restore my MacBook Pro from an external hard drive?
Click the Restore tab at the top of the Disk Utility window. Select the external hard drive that your cloned backup is stored next to “Restore From.” Select your Mac’s hard drive next to “Restore to.” Click Restore.
How do I install Mac OS on an external hard drive?
Click ‘Show All Disks,’ and then select your external drive. Click ‘Install.’ This version of macOS will now be installed on your external hard drive. Make sure the external drive is attached to your Mac. Hold down your Mac’s ‘Option’ key during startup. When prompted, select your external drive.
How long does it take to install OS X on an external hard drive?
Whichever method you choose, it will take anywhere from 15 to 30+ minutes to install OS X onto your external hard drive. While OS X is installing, your computer will restart a couple of times. Note that when it finally boots into OS X, that is the version running off your external drive.
How do I install a new version of macOS?
If you want to install a version of macOS that you previously downloaded from the App Store, then you can just re-download the necessary installer: Launch the App Store. Find the version of macOS that you want to install, and then click its accompanying ‘Install’ button. This will download the installer to your Mac’s ‘Applications’ folder.
Why do I need an external hard drive to run OS X?
This can be useful for a couple of different reasons. Firstly, it allows you to run another copy of OS X without needing any additional Mac computer. Also, since you can run a full copy of OS X on the external drive, it can be used for troubleshooting purposes on other Macs or it can be as a kind of virtual OS X.