Boot From External Disc Drive Mac

At this point, the Windows installer has copied all the files to the external drive, and has set up a boot environment that you can start your Mac from. Next time you boot from the external drive, Windows will complete the installation process. Restart Your Mac With the External Windows Drive. Sep 14, 2015 How to start up your Mac from an external USB storage device If your USB thumb drive, USB-based external disk or flash storage contains a usable operating system or an OS X installer, you can select it at boot time using OS X’S built-in feature called Startup Manager, which can be invoked via a simple keystroke. Jun 25, 2018 Boot Mac OS From External SSD HD Enclosure on Older iMac - Duration. Booting MacOS Off External Hard Drives - Why Would You Do That - Duration: 10:51. Craig Neidel 5,743 views. Also, you cannot boot from just any external hard drive. To be bootable, the external drive must be partitioned properly and contain an installation of the proper Mac operating system (OS). For PowerPC-based Macs, the external drive must be attached via FireWire, while Intel-based Macs can boot from either FireWire or USB external hard drives.

You can run macOS on a Mac in a variety of ways that we have already written an informative article about. In this article, we will focus on Mac startup mode with booting from a USB or an external hard drive.

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 Mac Boot From External Disk. Actually, it is possible to boot Mac from external drive or a hard drive, but there are a few specific requirements needed for. Also, you cannot boot from just any external hard drive. To be bootable, the external drive must be partitioned properly and contain an installation of the proper Mac operating system (OS). For PowerPC-based Macs, the external drive must be attached via FireWire, while Intel-based Macs can boot from either FireWire or USB external hard drives.

Starting a Mac with booting from an external disk may be necessary if you need to run another version or copy of macOS, other OS, fix any problems, and so on.

Plug in an external drive that you know is bootable. Go to System Preferences and Startup Disk. Click the padlock and enter your password, then try to choose that external drive to boot from. Dec 01, 2021 Create Bootable External Drive Mac Os X; Make External Hdd Bootable Mac Os X; Connect the external hard drive to your Mac. Launch Disk Utility (press Cmd + spacebar and start to type Disk Utility). Before this next step - if you are running High Sierra or later you will need.

To start the following conditions must be met:

  • The computer is based on the Intel system;
  • The volume is formatted with the choice of GUID section type;
  • Mac OS X v10.4.5 or later is installed on the USB storage device.

Read more:How to Use a External Hard Drive for Time Machine Backups?

How to Boot Mac from an external Hard Drive or USB device?

  • Connect a USB flash drive or external hard drive to your Mac.
  • Turn on your Mac by pressing the power button or restart your computer if it is already running;
  • Hold down the horkey for boots options: Option (Alt) key on the keyboard and hold until the boot menu appears;
  • Select the desired volume using the mouse, arrow or trackpad;
  • Press the Enter key to boot the Mac from the selected volume.


If Mac won’t boot from USB or volume is not displayed, wait a few seconds for the Download Manager to finish scanning the connected disks or use next tips, if it’s useless here the list of troubleshooting.

macOS does not Boot from an External Drive, what Should I Do?

  • Some older external USB drives require additional power. It is possible that it must be connected to an external power source or use a second USB on a Mac;
  • Make sure the external drive is turned on (again, the prerogative of old USB-drives);
  • Restore the disk access rights and correct the errors on it;
  • Make sure the disk is formatted with the choice of partition type GUID;
  • Try connecting an external drive to another USB port;
  • Make sure the external drive is bootable;
  • Connect the drive directly, without using a USB hub.

These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.

Download macOS

Find the appropriate download link in the upgrade instructions for each macOS version:

macOS Catalina, macOS Mojave, ormacOS High Sierra
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.

Boot Imac From External Drive

OS X El Capitan
El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

  1. Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended.
  2. Open Terminal, which is in the Utilities folder of your Applications folder.
  3. Type or paste one of the following commands in Terminal. These assume that the installer is still in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.

    High Sierra:*
    El Capitan:
  4. Press Return after typing the command.
  5. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
  6. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created.
  7. When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Catalina. You can now quit Terminal and eject the volume.

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument, similar to the way this argument is used in the command for El Capitan.

Use the bootable installer

Boot From External Disc Drive Mac

After creating the bootable installer, follow these steps to use it:

  1. Plug the bootable installer into a compatible Mac.
  2. Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Your Mac will start up to macOS Recovery.
    Learn about selecting a startup disk, including what to do if your Mac doesn't start up from it.
  3. Choose your language, if prompted.
  4. A bootable installer doesn't download macOS from the Internet, but it does require the Internet to get information specific to your Mac model, such as firmware updates. If you need to connect to a Wi-Fi network, use the Wi-Fi menu in the menu bar.
  5. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Can You Boot Mac Os On An External Hard Drive Windows 10

Learn more

For more information about the createinstallmedia command and the arguments that you can use with it, make sure that the macOS installer is in your Applications folder, then enter this path in Terminal:



High Sierra:

El Capitan:

Last week I described how I had been unable to get either of my M1 Macs to start up from an external disk. Thanks to many comments but no real clues, I’ve now been able to solve this, and here explain how you can do this too. Reliably.

You’ll need the following:

  • an M1 Mac; if you haven’t got one yet, I’m afraid it’s far too late for Christmas;
  • a Thunderbolt 3 SSD, such as a Samsung X5, freshly formatted in APFS (unencrypted) and connected to one of your M1 Mac’s Thunderbolt ports; if you only have SATA SSDs which connect via USB-C rather than Thunderbolt, you may be successful, but it seems unlikely. Some suggest that if your SSD isn’t Thunderbolt, try connecting it via a USB-A port, although that doesn’t help those with MacBook Air or Pro models;
  • a copy of the Big Sur 11.1 (or later) installer app, obtained from the App Store via Software Update; this procedure appears less reliable in macOS 11.0.1 and when installing macOS 11.0.1, so 11.1 is recommended for both.

Connect your external disk, and if there’s any doubt about whether it has been freshly formatted using APFS without encryption, use Disk Utility to do so before going any further. Then open the Install macOS Big Sur app, and proceed. When it invites you to select the disk on which you want to install Big Sur, if you don’t see your external disk, click on the button to show all available disks. Then select the external disk and click Continue.

Follow the installation process through to completion. This should be relatively rapid, and at the end your Mac will automatically restart into the freshly installed copy of Big Sur on your external disk.

With AppleID and current setups, what you now effectively have is not simply another boot disk, but a whole new Mac bar the hardware. You’ll have to go through the whole process of setting your AppleID to work, negotiating two-factor authentication for this ‘new Mac’, and so on, until you can finally use your external disk fully.

Can't Boot From External Dvd Drive

When you want to restart from the internal disk, the Startup Disk pane is your best option. M1 Macs lack the old Startup Manager, and holding the Option key during startup does nothing at all. Its new equivalent is in the opening of Recovery Mode. In the first screen displayed there, rather than select the Options item to proceed to Recovery, select the disk which you want to boot from and click Continue underneath it. Your M1 Mac will then restart from the selected disk.

Once booted from the internal disk again, ejecting the bootable external disk isn’t fault-free. Clicking on the Eject tool for the System disk brings a helpful dialog which offers to unmount both System and Data volumes. Oddly, on Intel Macs running Big Sur, the Data volume isn’t shown as a separate volume, but on M1 Macs it is.

Boot from external disc drive macbook air

Unfortunately, on an M1 Mac running macOS 11.1, the Data volume is usually left behind, and any attempt to eject it will result in your being told that it’s still in use, while trying to open the volume denies that it’s present at all.

In the end, I just disconnected the disk, and no howls of anguish came from the Mac.

Your bootable external disk now works with other M1 Macs, but not, as it stands, with Intel Macs. When I tried to start up from mine from Intel Recovery mode, macOS wanted to perform a “software update” before that might become possible. I suspect that this involves updating the hidden EFI partition, although curiously the Intel Mac saw my bootable disk with the name EFI in the first place. If you try to use the Startup Disk pane to restart an Intel Mac from an M1 bootable external disk, all that happens is that your Mac restarts from its internal disk and ignores your setting.

Buoyed by this success with an expensive Thunderbolt 3 SSD, I thought I might finally succeed in booting my M1 Mac mini from a much cheaper Samsung 860 EVO SSD in a USB-C enclosure. Installing macOS 11.1 on that external disk appeared to proceed identically until the installer reached the final minute, where it took much longer than the Thunderbolt disk had done.

Eventually, the installation completed, but the M1 Mac restarted from its internal disk, complaining that the external disk couldn’t be used for booting. This therefore appears to be a bug in current Big Sur installers, which don’t work reliably with some (if not most) external disks connected via USB-C rather than Thunderbolt. Trying to use Startup Disk on that external disk was similarly unsuccessful, with an error.

Even more strangely, when the Big Sur installer restarted my M1 Mac, its other USB-C SSD, which contains Time Machine backups, wasn’t mounted successfully. There thus appear to be multiple failures at work, probably including sealing of the new System and USB-C connection problems.

Boot From External Disc Drive Mac

If you’re trying to create and use a bootable external disk for M1 Macs, I therefore recommend that you don’t waste your time discovering which USB-C SSDs might be compatible: go straight for a Thunderbolt 3 enclosure. It’ll cost you more but save you time and effort in the long run. And you can definitely switch it between different M1 systems (I used my M1 Mac mini and M1 MacBook Pro), although you may not wish to try “updating” it to work with Intel Macs.