When you can’t boot up your Mac unit because of OS X-related errors, your only hope is the Disk Utility tool. The tool is used to repair Mac disk errors in your Mac such as corrupted files, non-responsive external devices, or the suddenly quitting of multiple apps. It can also be used to erase or reformat a disk, scan for physical errors on the disk, and repair disk permissions. Aside from Disk Utility, you can also use third-party tools to scan your computer for errors and pinpoint issues to resolve.
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![Repair startup disk mac Repair startup disk mac](/uploads/1/2/7/7/127761359/598263481.png)
But what if the problem is access to the Disk Utility or any 3rd party tools because your computer won’t start? Don’t worry, because your Mac can let you launch a standalone version the machine’s Disk Utility from your computer’s built-in recovery partition. The idea is to boot your Mac into Recovery Mode first and then run the repair function from there to repair the disk. You don’t need to use an external disk boot drive to resolve the error because you can do that using OS X’s Recovery Partition.
What is the Recovery Mode
Using Repair Disk Permissions. Launch Disk Utility and select your Mac in the list at the left of the app window. In the First Aid pane beside it look to the bottom left and you'll find two.
Recovery Mode is your Mac’s only hope when it encounters issues that prevent your computer from doing anything valuable. You have two options to fix it, the first one is to reinstall the updated version of your OS X and the 2nd option is to run a diagnostic scan using Disk Utility.
Reinstalling OS X can be done by rolling back to an earlier version using Time Machine, installing a new copy of your OS X over a pre-installed copy to fix some issues, or to completely erase the disk and install a fresh copy of your OS X. Your choice will depend on the type and the severity of your Mac disk error.
Here are the steps to follow on how to use Mac recovery mode to repair the disk errors:
Disk Repair Utility For Mac Os X Yosemite
- Go to the Apple Menu and click Restart.
- As your computer restarts, press Command + R when you hear the startup sound.
- Hold the key combination until the Apple logo appears.
- Choose Disk Utility when the OS X Utilities pop-up appears.
- Click Continue.
- Choose the volume you want to repair and then click the First Aid button.
- Click Repair Disk.
- There are two results that could happen after you run the Repair function: the disk has been repaired or you need to do something to fix the error.
- If the error says, overlapped extent allocation, this means that two or more files exist in the same space on your disk and one of them could be corrupted. Check each file on the list if you can replace or re-create it. If not, open the file and decide if you need to delete it.
- If the message says, the underlying task reported failure, this means that the repair was not successful and you have to run it again. If the repair still fails, back up your files and reformat the disk. Then, reinstall a fresh copy of the OS X. However, if the damage to the disk is physical, there is nothing you can do but replace it.
Other Options For You
But what if the Recovery Partition itself is damaged and you can’t access the recovery system? This usually happens when there’s a physical damage to the disk or you have replaced your startup disk.
In this case, your only option is to download an image of the Recovery System from Apple’s website and boot your Mac from it. This is called the Internet Recovery feature. However, this is only available for newer versions of Mac like OS X Lion. Internet Recovery has the same function as the Recovery Mode but you need to be connected to the Internet to be able to download the boot-up file from Apple’s servers.
To run the Internet Recovery feature, follow these steps:
- Go to Apple Menu and choose Restart.
- Hold down Command + Option + R when you hear the startup sound.
- If your computer is not connected to the Internet via Ethernet, you will be asked to connect to Wi-Fi.
- Once the Recovery System image has been downloaded, your Mac will start up with it and you’ll be able to access the same recovery tools of the regular Recovery Mode.
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See more information about Outbyte and uninstall instructions. Please review EULA and Privacy Policy.
Mac Disc Repair
Reinstall from macOS Recovery
macOS Recovery makes it easy to reinstall the Mac operating system, even if you need to erase your startup disk first. All you need is a connection to the Internet. If a wireless network is available, you can choose it from the Wi-Fi menu , which is also available in macOS Recovery.
1. Start up from macOS Recovery
To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following sets of keys on your keyboard. Release the keys when you see an Apple logo, spinning globe, or other startup screen.
Command (⌘)-R
Reinstall the latest macOS that was installed on your Mac (recommended).
Option-⌘-R
Upgrade to the latest macOS that is compatible with your Mac.
Shift-Option-⌘-R
Reinstall the macOS that came with your Mac, or the closest version still available.
You might be prompted to enter a password, such as a firmware password or the password of a user who is an administrator of this Mac. Enter the requested password to continue.
When you see the utilities window, you have started up from macOS Recovery.
2. Decide whether to erase (format) your disk
You probably don't need to erase, unless you're selling, trading in, or giving away your Mac, or you have an issue that requires you to erase. If you need to erase before installing macOS, select Disk Utility from the Utilities window, then click Continue. Learn more about when and how to erase.
3. Install macOS
When you're ready to reinstall macOS, choose Reinstall macOS from the Utilities window. Then click Continue and follow the onscreen instructions. You will be asked to choose a disk on which to install.
- If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
- If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
- If the installer is for a different version of macOS than you expected, learn about macOS Recovery exceptions.
- If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.
Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
If your Mac restarts to a setup assistant, but you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.
macOS Recovery exceptions
Disk Repair Tool Mac Os X
The version of macOS offered by macOS Recovery might vary in some cases:
- If macOS Sierra 10.12.4 or later has never been installed on this Mac, Option-Command-R installs the macOS that came with your Mac, or the closest version still available. And Shift-Option-Command-R isn't available.
- If you erased your entire disk instead of just the startup volume on that disk, macOS Recovery might offer only the macOS that came with your Mac, or the closest version still available. You can upgrade to a later version afterward.
- If your Mac has the Apple T2 Security Chip and you never installed a macOS update, Option-Command-R installs the latest macOS that was installed on your Mac.
- If you just had your Mac logic board replaced during a repair, macOS Recovery might offer only the latest macOS that is compatible with your Mac.
If you can't get macOS Recovery to offer the installer you want, you might be able to use one of the other ways to install macOS.
Other ways to install macOS
- You can also install macOS from the App Store or Software Update preferences. If you can't install macOS Catalina, you might be able to install an earlier macOS, such as macOS Mojave, High Sierra, Sierra, El Capitan, or Yosemite.
- Or create a bootable installer disk, then use that disk to install macOS on your Mac or another Mac.