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.
A sparse disk image is the same thing, only it takes up less space — for a while. Say you create a 30GB sparse disk image, and then drag a 1GB file onto it. Say you create a 30GB sparse disk. To create the images, the script creates an empty sparse disk image. Radmind is run relative to the root of this disk image, so the entire contents of the command file will be located locally. After radmind completes successfully, the disk image will be converted to a read-only format and compressed.
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
Start up from macOS Recovery, then select Disk Utility from the Utilities window. Click Continue.
If you're not repairing the disk your Mac started up from, you don't need to start up from macOS Recovery: just open Disk Utility from the Utilities folder of your Applications folder.
If you're not repairing the disk your Mac started up from, you don't need to start up from macOS Recovery: just open Disk Utility from the Utilities folder of your Applications folder.
Locate 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.
![Image Image](https://eshop.macsales.com/imgs/ndesc/mediafour/MEDMD100PEOWRB/MEDMD100PEOWRB_gall5.jpg)
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 item you selected, and continue to the next item.
- 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 disk2, 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
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 disk or Mac might need service. If you need help, please contact Apple Support.
These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.
Download macOS
Find the appropriate download link in the upgrade instructions for each macOS version:
macOS Catalina, macOS Mojave, ormacOS High Sierra
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.
OS X El Capitan
El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.
El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.
Use the 'createinstallmedia' command in Terminal
- Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended.
- Open Terminal, which is in the Utilities folder of your Applications folder.
- Type or paste one of the following commands in Terminal. These assume that the installer is still in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace
MyVolume
in these commands with the name of your volume.
Catalina:*
Mojave:*
High Sierra:*
El Capitan: - Press Return after typing the command.
- When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
- When prompted, type
Y
to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created. - When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Catalina. You can now quit Terminal and eject the volume.
* If your Mac is using macOS Sierra or earlier, include the
--applicationpath
argument, similar to the way this argument is used in the command for El Capitan.Use the bootable installer
Apple Sparse Disk Image Media Software
After creating the bootable installer, follow these steps to use it:
- Plug the bootable installer into a compatible Mac.
- Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Your Mac will start up to macOS Recovery.
Learn about selecting a startup disk, including what to do if your Mac doesn't start up from it. - Choose your language, if prompted.
- A bootable installer doesn't download macOS from the Internet, but it does require the Internet to get information specific to your Mac model, such as firmware updates. If you need to connect to a Wi-Fi network, use the Wi-Fi menu in the menu bar.
- Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.
Learn more
For more information about the
createinstallmedia
command and the arguments that you can use with it, make sure that the macOS installer is in your Applications folder, then enter this path in Terminal:Apple Sparse Disk Image Media Player
Catalina:
Apple Sparse Disk Image Media Markt
Macbook pro virus. Mojave:
High Sierra:
Apple Sparse Disk Image Media Encoder
El Capitan: