What is startup disk on Mac?

A Mac’s startup disk is its main drive—the one that holds the macOS operating system. It’s built into your MacBook, though you can boot from an external disk with an OS installed.

In most cases, your computer’s startup disk also holds all your software and user data, and like all other drives connected to your machine, you can view and manage the startup disk in Disk Utility. You can also see how your drive is being used and free up startup disk space on Mac in System Settings.

Why Mac shows ‘no startup disk’ error

When you see “no startup disk” on Mac, it may mean that your macOS install or other data on your drive is corrupted or has errors. You can boot into macOS Recovery to repair the startup disk with Disk Utility.

You may need to reinstall macOS to fix your startup disk, but if frequent disk errors persist even after a fresh OS install, there could be a more serious issue with your Mac. We recommend checking your Mac for the following problems:

1. Corrupted system files: If critical macOS files break down, your Mac won’t boot.
2. Disk permissions and file system errors: Other data errors or folders becoming inaccessible can also stop your OS from working properly.
3. Hardware issues: Many startup disk issues are the result of failing disk drives.
4. Software conflicts or recent updates: You may see startup disk errors after installing software that interferes with macOS, or if a recent update didn’t install correctly.

1. Corrupted system files

Damaged or missing system files will prevent your MacBook Air from recognizing macOS. We’ve also noticed that this issue, which is sometimes caused by interrupted macOS updates and even malware, can lead to your computer not detecting your startup disk at all.

2. Disk permissions and file system errors

We sometimes see Macs failing to boot and show no startup disk errors when there are errors in disk permissions or the file system, which prevent critical macOS files from being accessed or found. Fortunately, Disk Utility, built into macOS, can repair disk permissions on your Mac.

3. Hardware issues

If startup disk errors persist even after you’ve fixed corrupted system files or your Mac says not enough disk space but there is, we recommend checking your machine for hardware issues, such as a failing drive or logic board. Try booting from an external drive to see what the root cause may be.

4. Software conflicts or recent updates

Startup disk issues that occur immediately after installing new apps or macOS updates may be the result of software conflicts or installation errors. Failed macOS updates and third-party utilities that modify macOS in any way are especially likely to cause boot errors.

How to fix ‘no startup disk’ error on Mac

There are many solutions you can try to fix the “no startup disk” error on Mac, starting with a simple reset of your computer. If this doesn’t eliminate the issue, we suggest trying the following:

1. Restarting your Mac in Recovery mode.
2. Repairing your startup disk with Disk Utility.
3. Reinstalling macOS from Recovery.
4. Using third-party tools to repair disk.
5. Checking hardware and connection issues.
6. Select startup disk manually in Recovery mode.

1. Restarting your Mac in Recovery mode

The first step to take when you encounter a “no startup disk” error on Mac is to boot into Recovery mode, where you can access tools like Disk Utility. Restart your Mac in Recovery mode like so:

On an Apple Silicon Mac:

1. Shut down your Mac.
2. Press and hold the power button until Options appears on the screen.
3. Click Options, then click Continue.
4. If prompted, enter your Mac’s password, then click Continue to enter Recovery mode.

On an Intel Mac:

1. Restart your Mac.
2. Immediately press and hold the Command R keys on your keyboard.
3. If you see a lock, enter your Mac’s password.

2. Repairing your startup disk with Disk Utility

Once inside Recovery mode, we can use Disk Utility on Mac to run First Aid, which repairs disk permissions and other errors that can lead to startup disk errors. Here’s how:

1. In Recovery mode, select Disk Utility, then click Continue.
2. Select your Mac’s startup disk, usually called Macintosh HD, then click First Aid.
3. Click Run to confirm.
4. When First Aid has finished, click Done, then Restart your MacBook Pro.

3. Reinstalling macOS from Recovery

If you find that Disk Utility discovers errors that it cannot fix, you can try reinstalling macOS, which will replace any corrupted system files with fresh ones without deleting your data. Just follow these steps:

1. In Recovery mode, select Reinstall macOS, then click Continue.
2. Follow the on-screen instructions to complete the installation process. When asked to select a disk, ensure you select your current Mac startup disk.

We’ve found that reinstalling macOS like this usually fixes startup disk errors for good, but if you continue to run into issues, you can try formatting your drive and then installing a completely fresh copy of the OS. Bear in mind that this will delete all your data, so it should be a last resort.

4. Using third-party tools to repair disk

You may find that Disk Utility is unable to repair your startup drive, but that doesn’t necessarily mean the disk has failed. Before you pay for an expensive repair, try repairing the disk with third-party tools that can be more effective. We like OnyX because it’s highly rated and free, but other options are available.

Of course, you can only use a third-party disk repair tool if you can boot into macOS—or if you can remove your Mac’s startup disk and connect it to another machine as an external drive. If you can’t boot your Mac and its drive is soldered in, you’ll need to consider other options.

5. Checking hardware and connection issues

Unfortunately, a “no startup disk” message is occasionally caused by hardware failures. If you’re unable to successfully reinstall macOS—or Disk Utility can’t even detect your Mac’s internal drive—it’s possible the disk is damaged. When you can’t boot into Recovery mode at all, your Mac may have a faulty logic board.

If you have a Mac with a removable storage drive, or you’re trying to boot your machine from an external disk, ensure that the drive is seated properly or that the connection is secure. We also advise users to try a different cable when booting from external storage just in case that’s the issue.

6. Select startup disk manually in Recovery mode

Although it’s uncommon, we have seen that some Macs suddenly start trying to boot from the wrong disk, which can happen if the startup disk is corrupted, or if you’ve booted from an external disk in the past. Here’s how to ensure your Mac is selecting the correct startup disk:

1. In Recovery mode, click the Apple logo in the menu bar, then select Startup Disk.
2. Choose the correct startup disk for your Mac, then click Restart.

Your Mac should now continue to boot as normal.

Conclusion

While a “no startup disk” error can be alarming, it doesn’t always require an expensive trip to the Apple Store. There are steps you can take to fix the issue yourself, like running First Aid on your drive, reinstalling macOS, and making sure your macOS boot drive is properly connected.

If you’re unable to fix startup disk issues yourself, reach out to MacKeeper’s Premium Services to get expert help 24/7. Our team of professionals can guide you through the process of figuring out what’s causing a startup disk error—and what you need to do to fix it.

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