How to Use the Startup Disk Utility in Mac OS Mojave
Posted on 16th June 2023
What is the Startup Disk Utility?
The Startup Disk Utility is a tool that comes with every copy of the Mac OS. It allows you to select which volume you want to boot your Mac from, and can be used for startup troubleshooting.
How to Use the Startup Disk Utility
To select a startup volume:
1. Restart your Mac and hold down the Option key until the Startup Manager appears.
2. Select the volume you want to start up from.
3. Press the Return or Enter key.
To troubleshoot a startup issue:
1. Restart your Mac and hold down the D key until the Apple Diagnostics screen appears.
2. Select your language and continue.
3. Apple Diagnostics will run a series of tests on your Mac.
4. If any issues are found, they will be displayed on the screen.
5. Follow the instructions on the screen to resolve the issue.
3. Wipe the startup disk
If you’re selling or giving away your Mac, you’ll need to wipe the startup disk so that your personal data is erased. To do this, open the Startup Disk Utility and select the startup disk from the list of drives. Click the “Erase” button and choose a format type. We recommend using the “Mac OS Extended (Journaled)” option. Click “Erase” to confirm and wait for the process to complete.
4. Restore from a backup
If you have a backup of your Mac, you can use the Startup Disk Utility to restore it. To do this, open the utility and select the startup disk from the list of drives. Click the “Restore” button and choose the source of the backup. This can be a Time Machine backup or a disk image. Click “Restore” to confirm and wait for the process to complete.
5. Create a bootable installer
If you need to reinstall macOS, you can use the Startup Disk Utility to create a bootable installer. To do this, open the utility and select the startup disk from the list of drives. Click the “Create bootable installer” button and choose the location of the installer. This can be a USB flash drive or a hard drive. Click “Create” to confirm and wait for the process to complete.
The Startup Disk Utility is a handy tool that can be used to manage your Mac’s startup disk. With it, you can erase, restore, and create bootable installers.
Assuming you’ve followed the steps above and have your USB drive or other volume selected in the Startup Disk preferences pane, you can now click the Restart button. Your Mac will reboot from the selected volume.
If you’re using a Mac with a firmware password, you’ll be prompted to enter the password before you can select a startup volume. If you’ve forgotten your firmware password, you’ll need to visit an Apple Authorized Service Provider or an Apple Retail Store to have it reset.
Once your Mac has restarted from the selected volume, you can use Disk Utility to erase your internal startup volume and reinstall macOS, if necessary.
If you need to start up your Mac from a bootable installer, external storage device, or Windows volume, you can do so by holding down one of the following keys or key combinations while your Mac starts up.
Option key: Start up to Startup Manager, which allows you to choose a macOS volume or other startup disk.
Shift key: Start up in Safe Boot mode.
Command (⌘)-R: Start up from the built-in macOS Recovery system.
Command (⌘)-Option-R: Start up from macOS Recovery over the Internet.
Option-Command-R: Start up from macOS Recovery using the latest macOS that was installed on your Mac.
T: Start up in Target Disk mode, which allows you to access the built-in hard disk or SSD of another Mac using a Thunderbolt cable.
Command (⌘)-S: Start up in Single-User mode.
N: Start up from a NetBoot server, if your Mac supports network starting up.
Command (⌘)-V: Start up in Verbose mode.
C: Start up from a bootable CD, DVD, or other disc. You can use an optical disc that contains a bootable installer, such as macOS Catalina, or a disc with system-level diagnostic or repair tools.
D or Option-D: Start up to the Apple Diagnostics utility or Apple Hardware Test, depending on your Mac model.
O-F: Start up in Open Firmware.
X: Start up in macOS Recovery mode, or from macOS Internet Recovery if macOS Recovery isn’t available.
You can also start up your Mac in a variety of other modes, including Verbose mode, Single-User mode, and Target Disk mode. To do so, you’ll need to press and hold one or more keys while your Mac starts up.
To start up in Verbose mode, press and hold the Command (⌘) and V keys. Verbose mode shows every process that happens as your Mac starts up, and can be helpful for troubleshooting startup issues.
To start up in Single-User mode, press and hold the Command (⌘) and S keys. Single-User mode is a text-only interface that can be used to troubleshoot startup issues.
To start up in Target Disk mode, press and hold the T key. Target Disk mode allows you to access the built-in hard disk or SSD of another Mac using a Thunderbolt cable.
If you can’t start up from your internal startup volume, you may be able to start up from an external storage device, such as a USB flash drive or an external hard drive. To do so, you’ll need to connect the storage device to your Mac and then restart your Mac while holding down the Option key.
When you see the Startup Manager window, you should see your external storage device listed as a bootable volume. Select the volume and then click the arrow or press Return. Your Mac will then start up from the selected volume.
If your Mac is having trouble starting up from macOS, you can try starting up from macOS Recovery. To do so, restart your Mac while holding down the Command (⌘) and R keys.
When you see the macOS Recovery window, you can use the various tools available to troubleshoot your startup issue. For more information, see the Apple Support article Use macOS Recovery.
If you can’t start up from macOS Recovery, you may be able to start up from macOS Internet Recovery. To do so, restart your Mac while holding down the Option-Command-R keys.
When you see the macOS Recovery window, you can use the various tools available to troubleshoot your startup issue. For more information, see the Apple Support article Use macOS Recovery.
If you can’t start up from macOS Recovery or macOS Internet Recovery, you may be able to start up from a bootable installer. To do so, you’ll need to connect the bootable installer to your Mac and then restart your Mac while holding down the Option key.
When you see the Startup Manager window, you should see your bootable installer listed as a bootable volume. Select the volume and then click the arrow or press Return. Your Mac will then start up from the selected volume.
