How to Create Bootable USB Drive for Mac?
There are various ways to boot macOS. Aside from using the built-in Startup Manager, you can also boot into Verbose, Safe, and Target Disk modes. In addition to this, macOS users also have an option of picking a disk to boot the operating system from.
But let’s delve into something more specific. You’re about to find out how to boot your Mac up directly from external storage, specifically flash storage or a USB-based flash drive.
Why You Need to Boot from External Drive?
There are many occasions you may have trouble with your Mac.
- Corrupted system files and Mac crashes unexpectedly.
- Mac runs very slow with sufficient storage.
- You have deleted some system files wrongly.
- You couldn't login to your Mac.
- Troubleshooting purposes.
Let’s begin with the obvious question here; what are the basic requirements for creating bootable USB for Mac?
1. USB Drive
The macOS installer file is large with approximate size of 6 to 10GB depending upon the version. Also the process needs to sufficient storage space on your USB. So ensure to have at least 32GB or greater storage space on your USB drive.
Remember to copy and backup the USB since you need to delete the entire content for creating the bootable drive.
2. An Intel Based Mac
Apple transitioned to an Intel processors in 2005. In other words, if your Mac is not older than 2005, you should be fine.
3. Format USB Flash Drive to Apple File System
First, plug in your USB drive. Press "Command +Spacebar" to access Spotlight, then type “Disk Utility”. You can view the current file system of the USB drive. In our example, we have FAT32 file system which is compatible on Windows. You need to erase and format the USB to be compatible with your Mac.
Click on the “Erase” button on "Disk Utility" and choose the format as either APFS or Mac OS Extended. In most cases, your Mac will show the supported format by default and you don’t need to change it. On older Mac, you will see an additional scheme option, choose “GUID Partition Map”. Click on “Erase” button to continue further.
Disk Utility will delete all content on the USB and format it in the selected APFS or Mac OS Extended format.
4. MacOS Installer File
In order to create a bootable USB drive for Mac, you need download Mac OS installer. Open App Store on your Mac and search for the latest macOS version. Remember, App Store will only have the latest version which is macOS Mojave at this point when we write this article. Search for “macOS mojave” and click on the “Get” button.
This will start downloading the installer file to your “Applications” folder.
5. Creating USB Installer
After downloading, the installer will automatically ask you to install macOS Mojave. Simply quit the installer without starting the installation.
- At this point, ensure you have inserted the formatted USB drive, let’s say the name of the USB volume is “Boot Disk”.
- Also make sure the downloaded macOS installer file is in “Applications” folder.
- Press “Command + Spacebar” and search for “terminal” to open Terminal app.
- Copy and paste the below command in Terminal and hit enter.
- You need to enter admin password to proceed further.
- Terminal will ask you to confirm erasing the volume, press Y and hit enter to confirm.
- Now the erase disk process will start to copy the installer file on the USB drive. After successful completion of the process, name of the USB drive will be changed similar to the installer file name like “Install macOS Mojave”.
Note that Apple discourages booting with an earlier macOS version than the version your device is shipped with.
6. Boot Mac from USB
Follow the below process to boot your Mac from bootable USB:
- Insert the bootable USB installer drive and go to “Apple Menu > Restart”.
- When your Mac restarts, press and hold the Option key till “Startup Manager” opens.
- The Startup Manager scans and lists the drives that are connected and bootable.
- Note that the Startup Manager will only list volumes that include bootable volumes. If you only see "Macintosh HD" like below then the USB drive is not connected to your Mac or not created properly with the installer file.
- Select your Wi-Fi network name from the "Choose Network..." dropdown and enter the password to connect to internet. Remember, you need to have an internet connection for installing from USB as the installer needs to get updates for your Mac from Apple’s server.
- Double click on your USB that contains the macOS installer or highlight it and press the return key.
- You will see macOS Recovery app and choose “Install macOS” option from Utilities.
- It may take long time depending upon your Mac to start booting with macOS Mojave.