A cloned version of your macOS installation on a portable USB drive can be invaluable if your system won’t boot suddenly. It gives you troubleshooting options and even lets you work with an identical copy of your files. While internal hard drives are the best way to make bootable copies of your system, a USB drive can work too. This guide shows you how to install macOS on a USB drive.
How to Install macOS on a USB Drive
You should use Disk Utility for this method. First, in Disk Utility, right-click on the USB drive and click Erase.
Format your USB drive as Mac OS Extended (Journaled) and select the GUID partition mapping scheme.
If you can’t find the option to set the partition table, make sure you’re selecting the “View -> Show All Devices” option.
Right-click on the USB drive, click Erase, and select the partition table.
When the process is complete, download macOS. Unless you have a specific reason to install an older version of macOS, download the latest installer from the App Store.
It may take a while, given the size of macOS Big Sur (around 13GB). It can open and guide you through the installation process when the download is complete, but you don’t want to. Follow the instructions below to create a bootable installer in another way.
Open Terminal (found in the Utilities folder) and copy the snippet below. Note that you want to change the placeholder of your USB drive name:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/[your-usb-drive]
This code makes a couple of assumptions:
- You’re installing macOS Big Sur onto your USB drive.
- The downloaded installer will get stored in your Applications folder.
Of course, you have to change the file paths if neither of these apply. For other operating systems, Apple provides the necessary snippets.
As soon as you hit Enter, the installation process begins. Note that you will need to enter your administrator password and confirm that you want to erase the current drive.
Erasing the USB memory may take a while, but at some point you will be asked if the terminal can access the files on your USB memory. You must confirm that you can.
The installation process copies files from there to your USB stick. It will also rename the USB to whatever is configured for the installer you downloaded. In our example it is “Install macOS Big Sur”.
At this point, you can quit Terminal and eject the USB drive.
How to Clone Your Hard Drive to a USB Drive
If you have a USB drive large enough to store the data on your boot drive, you can create a direct clone of your boot drive. If you use the appropriate software, this floppy disk can also be booted.
There are many options here, although SuperDuper or Carbon Copy Cloner are fantastic. This tutorial uses Carbon Copy Cloner (CCC) to create a clone of your hard drive.
The process is super straightforward.
1. Select your boot drive as the source for the clone.
2. Set your USB drive as the target for the cloning operation.
3. Click “Start” to begin the cloning process. This will overwrite the contents of the USB drive and replace it with the bootable drive clone.
This is where you want to boot from the drive itself.
How to Boot Up from a USB Drive
After installing macOS on a USB drive or cloning your hard drive, you will need to restart your computer and boot from your USB drive.
You can run macOS from a bootable USB installation, much like you would from an internal drive. There is no operational difference between the two systems. However, running from a USB drive will be slower than the internal SSD.
To boot from your USB drive, set your bootable USB stick as the startup disk for the next startup in “System Preferences> Startup Disk” and then click “Restart” to restart your Mac.
Your Mac will reboot from USB instead of your standard startup disk. You can also use the Startup Manager to select your startup drive when you start macOS.
If you are using an Apple Silicon computer, you will need to insert the USB drive, shut down the Mac, then restart it, and hold down the power button until you reach the Startup Manager.
For Intel Macs, reboot and hold the Option key to open the boot selection dialog.
For any type of machine, use the arrow keys on your keyboard to select the USB drive from the list of boot devices, click to confirm and your USB drive will start to boot.
Now you can run the operating system normally and use this USB drive to start your Mac. Hard disk operations on the boot drive can also be safely performed from a USB memory stick.
Frequently Asked Questions
1. Can I split an installation across multiple USB drives?
In our experience, this will not be possible for you. Therefore, you will need a USB drive large enough to store Big Sur. We recommend 16GB to give you enough “headroom” during installation.
2. Am I able to use a USB connection other than USB-C?
Yes sir. Our tests gave us no problem using a USB 2.0 to USB-C port so you can get your older USB drives up and running.
3. Can I boot older versions of macOS from a USB drive?
Our tests were inconclusive here. In theory, there is no reason why you shouldn’t be able to boot an older version of macOS, and Apple offers ways to install older versions on a USB stick. However, if your Mac is based on Apple Silicon, you may encounter incompatibilities.
We also do not know if you will have problems installing an older operating system that you do not have. In short, we do not recommend it and it is probably not supported.
Wrapping Up
Linux users know that booting from a USB drive is a useful way to access the operating system. MacOS users can also install the operating system on a USB drive and work with the same installation as their internal drive (and faster). In fact, there are several ways to do this: you can use Disk Utility to format the drive before installing macOS, or you can clone your drive with a third-party tool.
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