How To Boot Mac Os From External Hard Drive

There have been several ways to create a bootable external drive of your internal drive for many years on macOS. However, it has become strenuous to get a bootable clone of your internal startup drive in recent versions of macOS. Close to impossible on customized macOS Big Sur and Monterey given the introduction of Apple's Cryptographic Signature Technology known as a Signed System Volume. The new addition prevents any external media from being bootable without a Signed System Volume. At this time, Apple is the only one capable of creating a Signed System Volume. We are not able to replicate or have a perfect workaround to this change.
In the past, we were able to create a stripped-down version of macOS and allow users to boot into it. We called this bootable external hard drive our Bootwell™ drive. While it still works on most Intel computers, on Apple M1, we were left searching for a suitable solution for our users to have a bootable clone of their internal drive. We found a workaround to our problems using one of Apple's utilities called Apple Software Restore (ASR). This feature creates a Signed System Volume with exact copies of all files with valid cryptographic signatures. In our test, we created a bootable external hard drive clone of the internal startup drive using ASR.

I need a bootable external drive to use in experimenting with different configurations, so following your advice, I just spent the better part of two days attempting to create a bootable macOS 11.1 external drive for my M1 Mac mini on either a Samsung X5 SSD or OWC Aura p12. (Both had been used as boot drives on the previous Intel Mac mini.). To start up a Mac from a bootable external hard drive, hold down the proper key combination while the computer is starting up. The exact key combinations that can be used vary slightly from one type of Mac to another. Also, you cannot boot from just any external hard drive.

Drawbacks to this external bootable drive are the required initial boot-up check on the first startup. This means that it can take around 20 to 30 mins for all the resources to come back to idle when first booting up into your external hard drive. Secondly, it is not always possible to boot into other systems that are not the ones that created the clone. This means you are only able to use this external bootable drive on the computer that created it.

Provided below are steps on creating a bootable external hard drive using the ASR utility. You can also use our clone tool built into the latest version of Drive Genius 6.
Disclaimer: We do not know how long this utility will work as it can be changed without notice.

Create a bootable external hard drive using ASR via terminal on macOS Monterey

1) We will want to find a suitable hard drive with enough free space to support your internal hard drives data. In this case, we are going to use the drive named Destination Drive. You can run the command “diskutil list“ to view all of the drives connected to the computer.

2) Reformat your drive to be compatible with your computer if you have not done this already (Do not do this if you already see your drive within finder).
To reformat the drive using Terminal you can use the command “diskutil erasedisk APFS Clone Destination /dev/disk4“ without the quotes (backslash () in this command line is used to escape a space in the volume name). “Clone Destination“ is the name you want to assign to the drive you will be reformatting. “/dev/disk4” is the name of the drive that will be reformatted. For this example, I am reformatting this 1TB drive named 'Destination Drive' shown in the previous image.

Note: All the data on this drive will be erased and overwritten when used for the clone. If you accidentally deleted a drive you were not supposed to. You can use Data Rescue to attempt to recover the lost files.
This 1TB drive is now formatted to APFS and contains “Clone Destination“ volume (APFS creates a virtual drive named container and is shown as “Synthesized“. However, you will only see on volume mounted in finder/desktop)

3) Run the command “sudo asr restore --no-personalization --source / --target /Volumes/Clone Destination/ --erase --verbose“ where “/Volumes/Clone Destination/“ is the name you assigned your destination drive. You will be prompted for your admin password before you are able to run the command. You will then be asked to confirm the deletion of all the data on the selected destination drive (Type “y” for yes and “n” to cancel).

4) The external hard drive will now look identical to your external hard drive. This drive is now bootable. You can reboot into the external drive by one of the following options.

ASR - Booting Options

  1. Shut down the computer

  2. Power on the computer while holding down the Option key until you see the apple loading bar.

  3. Select your external hard drive where we created the clone (Should be called Macintosh)

  1. Shut down the computer

  2. Power on the computer and continue to hold the power button until you see the boot drive options

  3. Select your external hard drive where we created the clone (Should be called Macintosh)

  4. You will be asked to Authenticate the startup disk using your admin User and password.

5) You will want to log into your profile and let the computer sit for about 20min. If you try and use the computer now. Things will be moving really slowly and you will most likely get a scroll wheel with any task that you run.

Commands used above

  • This command outputs a list of all the connected and internal hard drives. diskutil list shows you virtual hard drives, mounted disk images, and partitions allocated on the drive. You can identify your external hard drives by looking at the size and drive name. You can read more about diskutil by pulling up the manual using 'man diskutil' in Terminal.

  • This command will reformat the drive named /dev/disk4 to APFS and give the partition the name Clone Destination.

  • This command creates a clone of your internal startup drive onto the destination drive. This utility has other functionalities, however, we only want a bootable hard drive in this case. We found that allowing personalization was causing problems and failing in the process. This is why it is disabled in this guide.

Creating a bootable clone using Drive Genius on macOS Monterey

1) While within Drive Genius select your internal startup drive.

2) Select the Clone utility (You may be only be shown information about the clone utility if it has not been used before. Just select the start option at the bottom right-hand side) to move to the next window.

3) Here you will select the destination drive (The drive you are attempting to make bootable).

4) Once you click the start options Drive Genius will prepare the Destination Drive for you. It will start by reformatting the drive to APFS and begin to copy all of the files over to the destination drive. This process can take around an hour to complete, however, once complete you will be able to boot into the external hard drive by one of the following ways depending on your hardware. You can notice that both drives will look identical within finder. You can look into using our IconGenius to change the external drives icon.

  1. Shut down the computer

  2. Power on the computer while holding down the Option key until you see the apple loading bar.

  3. Select your external hard drive where we created the clone (Should be called Macintosh HD if you have not changed the name prior)

  1. Shut down the computer

  2. Power on the computer and continue to hold the power button until you see the boot drive options

  3. Select your external hard drive where we created the clone (Should be called Macintosh HD if you have not changed the name prior)

  4. You will be asked to Authenticate the startup disk using your admin User and password.

5) You will want to log into your profile and let the computer sit for about 20min. The system is running macOS verifications on all the files within this new disk since the boot drive changed. If you try and use the computer now. Things will be moving really slowly and you will most likely get a scroll wheel with any task that you run. The service that you will see taking up a lot of resources will be a process called XprotectServ which is apples built in antivirus tool.

We hope that this guide was able to help you create a bootable external hard drive while running macOS Monterey or Big Sur. However, ASR will only be temporary until we can find a suitable solution. Sign up to our mailing list to receive any changes to Drive Genius and our other products.

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

Jul 29, 2012 I'm not sure if you'd be able to do it from an external drive, but it is possible to boot OS X on a PC. However you need very specific components and either an EFI emulator or the internal dongle EFI-X. I just built an i7 Core system and dual boot OS X and Windows. Very quick and no glitches that I've encountered yet.

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.

External Hard Drive For Mac

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.

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.

In case, you want to recover any lost or deleted Mac files after a boot, we highly recommend you to go for Tenorshare Any Data Recovery for Mac. It is a utility data recovery tool capable of recovering any type of data from Mac with ease. Go for it!

  • Recover data deleted, formatted or lost on Mac;
  • Restore files from hard drive and external storage devices;
  • Recover data from failed/crashed/dead MacBook;
  • Fully supported latest macOS 10.15 Catalina;

Jul 10, 2020 • Filed to: Solve Mac Problems • Proven solutions

Creating a bootable drive for your Mac certainly seems to be a wise decision to make. Even though MacOS recovery partition can take care of all your recovery requirements in times of need, it’s still worthwhile to have a bootable installer.

Why Do You Need to Create A Bootable Drive For Your Mac?

  • The Mac installer gets deleted as soon as you download it and use it by installing the Mac operating system. Once the installer gets deleted, it means that you can no longer use it to install the MacOS on another Mac device. You will have to again download the installer on the latter Mac to install the MacOS. This can take a lot of time and become inefficient if you have multiple Macs.
  • Clean installs can be performed by installers which are very helpful in overwriting your start-up drive. You can also use this function for other troubleshooting issues as well.
  • When you have a bootable installer, it ensures that you are well guarded in an emergency scenario by making use of some of its helpful utilities.
  • A bootable installer can allow you to install an earlier version of MacOS and also let you temporarily boot into the previous version of the MacOS.

What Do You Need Before Creating Your Bootable Drive?

Before you begin the process, you will need the following:

  • USB Stick / External Hard Drive: If you are planning to use a USB for downloading the bootable version of the installer, make sure that it is 8GB in size or larger than that. In the case of Sierra, 12GB is recommended as the minimum requirement. Ideally, 32GB to 64GB is a good size to have as it is not only cost-effective but also gives a better performance. In the case of an external drive, you can use any spare one that you are not going to use for any other work.
  • Download MacOS High Sierra Installer: It is important to note that once you have downloaded the installer, it will begin with the installation process on its own. You can close the installer just like you quit any Mac app. In the case of the macOS version being older than the current one, you can click on ‘ok’ once the message flashes that the version is too old to install. You can find the old installer file in your ‘Application Folder’. Don’t forget to take a backup of your Mac to be on a safe side.

Part 1. How to Create a Bootable Drive Using Terminal

There are two ways of creating a bootable copy of the installer. You can either use Terminal or get the job done through a free software like Recoverit to do it for you. First, let us look at how to create a bootable drive using Terminal.

Steps to create a MacOS Siera beta boot disk:

  1. The first step in the process is to connect your external hard drive to your Mac. You need to name your external drive ‘untitled’ for the Terminal command to work.
  2. Launch Terminal. You can find this in the 'Utilities' folder of your Applications folder.
  3. Copy the following instructions now:
  4. sudo /Applications/Install macOS --volume /Volumes/Untitled --applicationpath /Applications/Install macOS
  5. In this step, you have to paste the copied instruction on the screen by going back to the Terminal.
  6. You will be required to feed in your user password now and then hit ‘Return’.
  7. Now, the Terminal will ask for your permission to erase the drive. To continue, type ‘Y’ and again hit return.
  8. After the Terminal has erased your drive, your Mac will prompt you if you wish to use the drive for Time Machine. Click ‘Don’t Use’.
  9. Next, the installer file will be copied by the Terminal to your drive. This might take some time, so be patient.
  10. Once the copying is completed, a ‘Copy complete’ message will be displayed on your screen. You can now quit the Terminal and use your drive.

Part 2. How to Create Bootable Media for Mac with Recoverit Mac Data Recovery

Recoverit Mac data recovery software is one of the most impressive and easy-to-use data recovery software in the market, and it has lots to offer with its varied utilities and functions. With Recoverit to create bootable media, you can access your system easily without the need to reinstall the MacOS to recover your lost data.

Step 1 Launch Recoverit and get to select 'Computer Crash Recovery'. Click 'Start'.

Boot Imac From External Drive

Step 2 Choose your connected external hard drive as the bootable media, and click 'Start'. You will receive a requirement of formatting the device. Before the formatting, remember to back your drive data up.

Step 3 Wait for a while, and Recoverit will format your drive and start creating the bootable media.

Step 4 Once it finishes, follow the next steps to restore data back.

Boot Mac From Ssd

Part 3. How to Set the Computer Boot from the Bootable Media

Step 1 Connect your external drive to your unbootable Mac.

Step 2 Press down on the ‘Option’ key after restarting your Mac.

Mac Os Download

Step 3 Once the booting has finished, your Mac will display the Startup Manager to show you the available boot drives. Select your external hard drive and hit ‘Return’.

Step 4 If you want to install Sierra but keep your data untouched, you can select 'Install OS X'. However, if you wish to delete all your data, then you can select Disk Utility to format the entire drive and wipe away all your data to reformat the internal drive first and then install MacOS Sierra.

You now have a bootable copy of the MacOS Sierra installer, and you can use it on multiple Macs to install the Mac OS. If you are familiar with the command line, you can opt to create a bootable drive using Terminal. For others, you can simply opt for reliable Mac hard drive recovery software like Recoverit and assist you in recovering your data as well from crashed systems in case of emergencies.

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