Boot Your Computer From an External USB Device: A Comprehensive Guide

Do you ever find yourself in a situation where you need to use a different operating system or boot your computer from an external device? Whether it's a Linux distribution, macOS, or a Windows installation, you can indeed boot your computer from an external USB device like an SSD or HDD. This article provides a comprehensive guide on how to achieve this, covering both live Linux distros and macOS.

Booting from an External USB Device: An Introduction

The process of booting from an external USB device is quite straightforward and is commonly used for Live Linux systems. However, it can be applied to other systems as well. The primary requirements are that the external device must be formatted to be bootable and should contain a complete system such as Linux, Windows, or macOS.

Key Concepts and Tools

There are many free utilities like Rufus and Unetbootin that simplify the process of creating a bootable USB drive. These tools allow you to download the ISO file for the desired operating system and copy it to the USB device with a few simple steps.

Formating the External Drive

Step 1: Open Disk Utility

First, ensure that you format the target USB drive to a supported file system, such as APFS. Here's the step-by-step process:

Open Disk Utility (you may need to search for it in Applications). Select the external drive you wish to format, making sure it is the one you intend to use and not your Mac's internal drive. Click on the "Erase" button. Select APFS from the "Format" dropdown menu. Ensure it is the standard version without encryption features. Name the drive appropriately. Click "Erase" and then "Done" to finalize the process.

Installing macOS on an External Drive

Once the drive is properly formatted, you can install macOS on it. Here are the steps to follow:

Open the Mac App Store and download the macOS installer. Follow the on-screen instructions in the installer, including clicking "Continue." When the installer prompts you to select the drive to install macOS to, choose the APFS-formatted external drive you intend to make bootable. Proceed with the installation.

After the installation is complete, the Mac will restart and should automatically boot from the external disk.

Boot Your Mac Using an External Drive

If for some reason your Mac does not boot from the external drive, follow these steps:

Power off your Mac. Connect the external bootable drive to the USB port. Turn your Mac back on and hold down the power button until you see the startup options menu. Select the bootable external drive from the startup options list.

Your Mac will boot from the external drive instead of the internal storage. This process is essential for troubleshooting, installing different operating systems, or creating a bootable backup of your Mac.

Conclusion

Booting from an external USB device, whether for a Linux distro or macOS, offers a flexible and powerful solution for system administrators, developers, or anyone who needs to run a different operating system or troubleshoot their Mac. By following the steps outlined in this guide, you can easily set up and boot from an external storage device, enhancing your computing experience and efficiency.