If you’re having problems with a disk, Disk Utility can check the disk and repair problems it detects. How to repair a disk To explore the Disk Utility User Guide, click Table of Contents at the top of the page, or enter a word or phrase in the search field. If you’ve never had Yosemite on this Mac, the first thing to do is visit the Mac App Store, download Yosemite, and install it. Once you’ve done that, here’s how to install, reinstall, or upgrade Yosemite, step by step: Boot from your Recovery HD partition by restarting your Mac while holding down the Command+R keys.
System Disk Utility 2.6.2 for Mac OS X Server 1.2 is a Mac OS program that allows you to select which hard disk your computer will start up from.
Disk Utility can find and repair errors related to the formatting and directory structure of a Mac disk. Errors can lead to unexpected behavior when using your Mac, and significant errors might even prevent your Mac from starting up completely.
Before proceeding, make sure that you have a current backup of your Mac, in case you need to recover damaged files or Disk Utility finds errors that it can't repair.
Open Disk Utility
In general, you can just open Disk Utility from the Utilities folder of your Applications folder. However, if your Mac doesn't start up all the way, or you want to repair the disk your Mac starts up from, open Disk Utility from macOS Recovery:
- Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:
- Apple silicon: Turn on your Mac and continue to press and hold the power button until you see the startup options window. Click the gear icon labeled Options, then click Continue.
- Intel processor: Turn on your Mac, then immediately press and hold these two keys until you see an Apple logo or other image: Command (⌘) and R.
- You may be asked to select a user you know the password for. Select the user, then click Next and enter their administrator password.
- From the utilities window in macOS Recovery, select Disk Utility and click Continue.
Select your disk in Disk Utility
Choose View > Show All Devices (if available) from the menu bar or toolbar in Disk Utility.
The sidebar in Disk Utility should now show each available disk or other storage device, beginning with your startup disk. And beneath each disk you should see any containers and volumes on that disk. Don't see your disk?
In this example, the startup disk (APPLE HDD) has one container and two volumes (Macintosh HD, Macintosh HD - Data). Your disk might not have a container, and it might have a different number of volumes.
Repair volumes, then containers, then disks
For each disk that you're repairing, start by selecting the last volume on that disk, then click the First Aid button or tab.
In this example, the last volume on the disk is Macintosh HD - Data.
Click Run to begin checking the selected volume for errors.
- If there is no Run button, click the Repair Disk button instead.
- If the button is dimmed and you can't click it, skip this step for the disk, container, or volume you selected.
- If you're asked for a password to unlock the disk, enter your administrator password.
After Disk Utility is done checking the volume, select the next item above it in the sidebar, then run First Aid again. Keep moving up the list, running First Aid for each volume on the disk, then each container on the disk, then finally the disk itself.
In this example, the repair order is Macintosh HD - Data, then Macintosh HD, then Container disk3, then APPLE HDD.
If Disk Utility found errors that it can't repair
If Disk Utility found errors that it could not repair, use Disk Utility to erase (format) your disk.
If your disk doesn't appear in Disk Utility
Mac Disk Utility For Windows
If Disk Utility can't see your disk, it also can't see any containers or volumes on that disk. In that case, follow these steps:
- Shut down your Mac, then unplug all nonessential devices from your Mac.
- If you're repairing an external drive, make sure that it's connected directly to your Mac using a cable that you know is good. Then turn the drive off and back on.
- If your disk still doesn't appear in Disk Utility, your Mac might need service. If you need help, please contact Apple Support.
- Supported version: 0.6.5
While you don't need a fresh install of macOS to use OpenCore, some users prefer having a fresh slate with their boot manager upgrades.
To start we'll want to grab ourselves a copy of macOS. You can skip this and head to formatting the USB if you're just making a bootable OpenCore stick and not an installer. For everyone else, you can either download macOS from the App Store or with Munki's script.
# Downloading macOS: Modern OS
- This method allows you to download macOS 10.13 and newer, for 10.12 and older see Downloading macOS: Legacy OS
From a macOS machine that meets the requirements of the OS version you want to install, go directly to the App Store and download the desired OS release and continue to Setting up the installer.
For machines that need a specific OS release or can't download from the App Store, you can use the Munki's InstallInstallMacOS utility.
In order to run it, just copy and paste the below command in a terminal window:
As you can see, we get a nice list of macOS installers. If you need a particular versions of macOS, you can select it by typing the number next to it. For this example we'll choose 10:
- macOS 11, Big Sur Note: As this OS is quite new, there's still some issues with certain systems to resolve. For more information, see here: OpenCore and macOS 11: Big Sur
- For first time users, we recommend macOS 10.15, Catalina
- Nvidia GPU Note: Reminder to verify whether your hardware support newer OSes, see Hardware Limitations
This is going to take a while as we're downloading the entire 8GB+ macOS installer, so it's highly recommended to read the rest of the guide while you wait.
Once finished, you'll find in your ~/macOS-Installer/ folder a DMG containing the macOS Installer, called Install_macOS_11.1-20C69.dmg for example. Mount it and you'll find the installer application.
- Note: We recommend to move the Install macOS.app into the
/Applicationsfolder, as we'll be executing commands from there. - Note 2: Running Cmd+Shift+G in Finder will allow you to easily jump to
~/macOS-installer
From here, jump to Setting up the installer to finish your work.
# Downloading macOS: Legacy OS
- This method allows you to download much older versions of OS X, currently supporting all Intel versions of OS X(10.4 to current)
# Legacy macOS: Offline method
This method allows us to download full installers from Apple, however is limited to 10.10, Yosemite, so older OSes will need to be grabbed via the 'Online Method' mentioned below.
To start, go to the following link:
Download your desired version and a .pkg file should be provided.
Depending on what OS you're on, you can run this script and head to Setting up the installer however if you receive this error:
This means we'll need to manually extract the installer.
# Extracting the Installer
To start, grab the InstallMacOSX/InstallOS.dmg and mount it:
Next, let's open up terminal window and make a folder on our desktop to break things. Run one at a time:
Now we get to the fun part, extracting the installer(Note this may take a few minutes):
- For El Capitan(10.11) and older:
- For Sierra(10.12):
Next, run the following(one at a time):
- Yosemite:
- El Capitan:
- Sierra:
Once this is done, you can head to Setting up the installer!
# Legacy macOS: Online method
This method allows us to download legacy versions of macOS including 10.7 to current, however these are only recovery installers so require an internet connection inside the installer itself
To start, you'll want to use macrecovery.py instead. This tool is actually already bundled in OpenCorePkg:
Instructions for running are quite simple, choose from one of the below commands depending on which OS you want to download:
From here, run one of those commands in terminal and once finished you'll get an output similar to this:
Once this is done, format your USB as FAT32 with GUID Partition Scheme:
And finally, create folder on the root of this drive called com.apple.recovery.boot and place the newly downloaded BaseSystem/RecoveryImage files in:
From here, you can skip to Setting up OpenCore's EFI environment
# Legacy macOS: Disk Images
This method instead relies on hosted images either from Apple or Acidanthera, and restoring onto your drive.
# Acidanthera Images
The below installers were pulled from genuine Mac restore disks with their SMBIOS lock removed, contents of OS X itself have not been modified in any way.
# Apple Images
Note that these images require you to have an Apple Developer account to access.
# Restoring the drive
Now comes the fun part, you'll first want to open the dmg you just downloaded and have it mounted. Now open Disk Utility and format your drive as macOS Extended(HFS+) with a GUID partition map:
Next we have 2 options to follow:
- ASR Restore(Apple Software Restore)
- Terminal based, works with SIP enabled
- Disk Utility Restore
- May require SIP disabled in newer OSes
# ASR
Here you'll simply want to open terminal and run the following:
- Note: This may not align with your setup, please change accordingly:
- Change
/Volumes/Mac OS X Install DVDto what your mounted Disk Image is called - Change
/Volumes/MyVolumeto what your USB is called
- Change
This will take some time but once you're finished, you can skip to Setting up OpenCore's EFI environment
# Disk Utility
Due to some pesky issues with Disk Utility, many restores can fail if SIP is enabled. If you have issues we recommend either using the ASR Method or disable SIP.
To start, open Disk Utility and you should see both your USB drive and the Disk Image in the sidebar. From here, select restore
This will take some time but once you're finished, you can skip to Setting up OpenCore's EFI environment
If you get an error such as this one during restore:
This likely means SIP needs to be disabled, however we recommend using ASR Method instead.
# Setting up the installer
Now we'll be formatting the USB to prep for both the macOS installer and OpenCore. We'll want to use macOS Extended (HFS+) with a GUID partition map. This will create two partitions: the main MyVolume and a second called EFI which is used as a boot partition where your firmware will check for boot files.
- Note: By default, Disk Utility only shows partitions – press Cmd/Win+2 to show all devices (alternatively you can press the View button)
- Note 2: Users following 'Legacy macOS: Online method' section can skip to Setting up OpenCore's EFI environment
Next run the createinstallmedia command provided by Apple(opens new window). Note that the command is made for USB's formatted with the name MyVolume:
This will take some time so you may want to grab a coffee or continue reading the guide (to be fair you really shouldn't be following this guide step by step without reading the whole thing first).
You can also replace the createinstallmedia path with that of where your installer's located (same idea with the drive name).
Pulled from Apple's own site: How to create a bootable installer for macOS(opens new window)
# Legacy Setup
For systems not supporting UEFI boot, see below:
To start, you need the following:
- BootInstall_IA32.tool or BootInstall_X64.tool
- This can be found in OpenCorePkg under
/Utilties/LegacyBoot/
- This can be found in OpenCorePkg under
- Install USB(Created above)
Within your OpenCore build folder, navigate to Utilities/LegacyBoot. Here you'll find a file called BootInstall_ARCH.tool. What this does is install DuetPkg to your desired drive.
Now run this tool in terminal with sudo(This tool will likely fail otherwise):
This will give you a list of available disks, choose yours and you will be prompted to write a new MBR. Choose yes[y] and you'll be finished.
This will provide you with an EFI partition with either a bootia32 or bootx64 file
# Setting up OpenCore's EFI environment
Setting up OpenCore's EFI environment is simple – all you need to do is mount our EFI system partition. This is automatically made when we format with GUID but is unmounted by default, this is where our friend MountEFI(opens new window) comes in:
Download Disk Utility For Windows
You'll notice that once we open the EFI partition, it's empty. This is where the fun begins.
Mac Os Disk Utility Download
# Now with all of this done, head to Setting up the EFI to finish up your work