Booting From An External Hard Drive Mac Os X

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The Best Tech Newsletter Anywhere. Join 250,000 subscribers and get a daily digest of news, geek trivia, and our feature articles. Jul 31, 2018 By default, Mac starts from its built-in hard disk, but a startup disk can be any storage device that contains bootable contents that compatible with your Mac. For example, if you install macOS or Microsoft Windows on a USB drive, your Mac can recognize that drive as a startup disk. This guide provides 2 ways to boot a Mac from a USB flash drive.

by Jenefey AaronUpdated on 2020-01-10 / Update for OS X

You may need to boot up your Mac using an external drive or boot volume once in a while, rather than using a start up disk. Booting with an external disk has a lot of significance. Maybe you want to troubleshoot some problems, repair the disk, do partitions, format the entire disk, update, and install OS X etc. All these are executed perfectly when you use an external boot volume to boot up your Mac. In this article, we are here with the detailed step by step guide on how to boot Mac from external hard drive easily. So, let's get started…

Part 1: How to Boot Mac from USB Drive/CD/DVD

Actually, it is possible to boot Mac from external drive or a hard drive, but there are a few specific requirements needed for your Mac to become eligible for that process.

  • First, you have to have an Intel-Based Mac.
  • Second, the CD or DVD you are using to boot must contain Apple’s Super Drive or if you are using a USB drive then it should be formatted with GUID Partition, and you are also required to install OS X installer. Apple is against booting Mac from an external storage device, because you may install an older version of OS X than the one you were using.

Boot from CD or DVD:

If you want to boot your MacBook/Air/Pro/iMac from an optical media like CD or DVD you need to follow the steps below:

1. Open your Mac or restart the device if you were already using it.

2. When the startup music is playing press and hold the “C” key from the keyboard.

3. This will start the OS X installer from the CD/DVD on your Mac.

So, it is not too complicated to Mac boot from CD/DVD. You can easily burn a bootable image of OS X on a DVD by using Disk Utility.

Boot from External USB:

Using your USB drive to boot Mac is not as simple as you think. You need to prepare your USB drive beforehand for this specific purpose. You have to format the USB drive and insert the proper Operating System, which is OS X.

1. Turn on your Mac.

2. As soon as the startup music begins you need to press and keep holding the 'Option' key.

3. After that release that key, the Startup manager will be launched.

4. Startup Manager will begin scanning your device and you will be provided with a list of devices that are connected to your Mac.

5. Now, select the drive you want to use with your mouse.

6. Finally, press 'Return' key on the selected option to boot Mac.

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This way you can boot your Mac with an external USB drive, but the most critical part is to prepare the USB drive. If you have multiple USB drives connected, then the Startup Manager shall list the drives with the bootable OS. So, this is how to boot Mac from USB drive.

Part 2: Common Problems and Fixes When Boot Mac from External Drive

You may face several issues during MacBook Pro Boot from USB or any external drive. So, a few FAQs are mentioned below which may help you when you are facing any difficulties.

  • 1. Have you tried connecting to a different USB port?

    • If you are unable to startup the installer after connecting the USB drive to your Mac, then first you should try connecting it to a different USB port. It may fix the problem.

  • 2. Have you formatted the USB drive with GUID partition?

    • If you are having problems with your USB storage device then you need to make sure that if you have properly formatted the drive with GUID partition. You have to do it properly otherwise the Intel-Based Mac won't start.

  • 3. Is your Mac shutting down after connecting the disk?

    • Actually, the MacBook contains a preventive measure and because of that computer shuts down automatically when a damaged USB drive is connected or if the USB port itself is damaged.

  • 4. Is your Disk needs repair?

    • If your Mac fails to boot from an external drive even though you have properly installed the OS X installer, then maybe your disk is damaged. You should open Disk Utility and ask permission to repair disk.

  • 5. Have you connected the USB drive properly?

    • There are two types of Apple keyboards, Wired and Wireless. There are also some keyboards with inbuilt USB ports but they may not have enough power to run the drive.

So, this is how to startup Mac from external drive. Follow the frequently asked questions to clear any doubts that you have while booting from external hard drive Mac.

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Reinstall from macOS Recovery

macOS Recovery makes it easy to reinstall the Mac operating system, even if you need to erase your startup disk first. All you need is a connection to the Internet. If a wireless network is available, you can choose it from the Wi-Fi menu , which is also available in macOS Recovery.

1. Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following sets of keys on your keyboard. Release the keys when you see an Apple logo, spinning globe, or other startup screen.

Command (⌘)-R

Reinstall the latest macOS that was installed on your Mac (recommended).

Option-⌘-R

Upgrade to the latest macOS that is compatible with your Mac.

Shift-Option-⌘-R

Reinstall the macOS that came with your Mac, or the closest version still available.

You might be prompted to enter a password, such as a firmware password or the password of a user who is an administrator of this Mac. Enter the requested password to continue.

When you see the utilities window, you have started up from macOS Recovery.

2. Decide whether to erase (format) your disk

You probably don't need to erase, unless you're selling, trading in, or giving away your Mac, or you have an issue that requires you to erase. If you need to erase before installing macOS, select Disk Utility from the Utilities window, then click Continue. Learn more about when and how to erase.

3. Install macOS

When you're ready to reinstall macOS, choose Reinstall macOS from the Utilities window. Then click Continue and follow the onscreen instructions. You will be asked to choose a disk on which to install.

How To Make An External Hard Drive Bootable Mac Os X

  • If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
  • If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
  • If the installer is for a different version of macOS than you expected, learn about macOS Recovery exceptions.
  • If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.

Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

If your Mac restarts to a setup assistant, but you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

macOS Recovery exceptions

The version of macOS offered by macOS Recovery might vary in some cases:

  • If macOS Sierra 10.12.4 or later has never been installed on this Mac, Option-Command-R installs the macOS that came with your Mac, or the closest version still available. And Shift-Option-Command-R isn't available.
  • If you erased your entire disk instead of just the startup volume on that disk, macOS Recovery might offer only the macOS that came with your Mac, or the closest version still available. You can upgrade to a later version afterward.
  • If your Mac has the Apple T2 Security Chip and you never installed a macOS update, Option-Command-R installs the latest macOS that was installed on your Mac.
  • If you just had your Mac logic board replaced during a repair, macOS Recovery might offer only the latest macOS that is compatible with your Mac.

If you can't get macOS Recovery to offer the installer you want, you might be able to use one of the other ways to install macOS.

Booting From An External Hard Drive Mac Os X Download

Other ways to install macOS

Os X Boot From External Drive

  • You can also install macOS from the App Store or Software Update preferences. If you can't install macOS Catalina, you might be able to install an earlier macOS, such as macOS Mojave, High Sierra, Sierra, El Capitan, or Yosemite.
  • Or create a bootable installer disk, then use that disk to install macOS on your Mac or another Mac.