Disk Utility (Yosemite): Create a disk image

Create a disk image
Create a disk image using Disk Utility

Use Disk Utility to create disk images.

Open Disk Utility for me

Disk image and open disk image partition

Create a blank disk image to burn

Create an empty disk image, fill it with data, then use it to create disks, CDs, or DVDs.

  1. Choose File > New > Blank Disk Image.

  2. Enter a name for the disk image, then choose where to save it.

  3. In the Name field, enter the name for the disk image (the name appears when you open the disk image).

  4. Click the Size pop-up menu, then choose the size of the disk image.

  5. Click the Format pop-up menu, then choose the format for the disk:

    • If the disk will be used with Mac computers, choose any one of the Mac OS Extended formats.

    • If the disk will be used with Windows or Mac computers and is 32 GB or less, choose MS-DOS (FAT).

    • If the disk will be used with Windows or Mac computers and is over 32 GB, choose ExFAT.

  6. To encrypt the disk image, click the Encryption pop-up menu, then choose an encryption option.

  7. Click the Partitions pop-up menu, then choose a partition layout.

  8. Click the Image Format pop-up menu, then choose read/write disk image.

  9. Click Create.

    Disk Utility creates the disk image and mounts its disk icon on your desktop.

  10. In the Finder, copy your files to the disk, then eject it.

  11. Restore the disk image to a disk, or burn it to a CD or DVD.

Create a disk image from a disk or connected device

Create a disk image that includes the data and free space on a disk or connected device, such as a USB device. For example, if a USB device or partition is 80 GB with 10 GB of data, the disk image will be 80 GB in size and include data and free space. You can then restore that disk image to another disk or burn it to a CD or DVD.

  1. Select a disk, partition, or connected device in the sidebar.

  2. Choose File > New, then choose “Disk Image from device name.”

  3. Enter a name for the disk image, then choose where to save it.

  4. Click the Image Format pop-up menu, then choose an option:

    • Read-only: The disk image can’t be written to, and is quicker to create and open.

    • Compressed: Compresses data, so the disk image is smaller than the original data. The disk image is read-only.

    • Read/write: Allows you to add files to the disk image after it’s created.

    • DVD/CD master: Can be used with third-party apps. It includes a copy of all sectors of the disk image, whether they’re used or not. When you use a master disk image to create other DVDs or CDs, all data is copied exactly.

  5. To encrypt the disk image, click the Encryption pop-up menu, then choose an encryption option.

  6. Click Save.

For technical information about creating a restore disk image, see the Apple Software Restore (ASR) manual (man) page.

Create a disk image from a folder or connected device

Create a disk image that contains the contents of a folder or connected device, such as a USB device. You can then restore that disk image to another disk or burn it to a CD or DVD.

  1. Choose File > New, then choose Disk Image from Folder.

  2. Select the folder or connected device in the dialog that appears, then click Image.

  3. Enter a name for the disk image, then choose where to save it.

  4. Click the Image Format pop-up menu, then choose an option:

    • Read-only: The disk image can’t be written to, and is quicker to create and open.

    • Compressed: Compresses data, so the disk image is smaller than the original data. The disk image is read-only.

    • Read/write: Allows you to add files to the disk image after it’s created.

    • DVD/CD master: Can be used with third-party apps. It includes a copy of all sectors of the disk image, whether they’re used or not. When you use a master disk image to create other DVDs or CDs, all data is copied exactly.

    • Hybrid image (HFS+/ISO/UDF): This disk image is a combination of disk image formats and can be used with different file system standards, such as HFS, ISO, and UDF.

  5. To encrypt the disk image, click the Encryption pop-up menu, then choose an encryption option.

  6. Click Save.

For technical information about creating a restore disk image, see the Apple Software Restore (ASR) manual (man) page.

Protect confidential documents in a secure disk image

If you have confidential documents that you don’t want others to see without your permission, you can put them in an encrypted disk image.

Note:   If you want to protect the contents of your entire home directory, turn on FileVault using the FileVault pane of Security & Privacy Preferences.

  1. Choose File > New > Blank Disk Image.

  2. Enter a name for the image, then choose where to save it.

    This will be the name of the file that contains the disk image.

  3. In the Name field, enter a name for the disk image (the name appear when you open the disk image).

    The image file and the disk image can have the same name.

  4. Click the Size pop-up menu, then choose the size of the disk image.

    Be sure you choose a size that’s large enough to hold any changes and new documents you might add.

  5. Click the Encryption pop-up menu, then choose an encryption option.

  6. Use the default settings for the rest of the options:

    • Click the Format pop-up menu, then choose Mac OS Extended (Journaled).

    • Click the Partitions pop-up menu, then choose Single partition - Apple Partition Map.

    • Click the Image Format pop-up menu, then choose read/write disk image.

  7. Click Create.

  8. Enter a password, deselect “Remember password in my keychain,” then click OK.

    Note:   If you leave “Remember password in my keychain” selected, anyone with access to your computer may be able to open the disk image without entering the password.

    Disk Utility creates the disk image, and you’ll see it on your desktop.

  9. Copy the documents you want to protect to the disk image.

  10. If you want to erase the original documents so they can’t be recovered, drag them to the Trash, then choose Finder > Secure Empty Trash.

When you’re finished using the documents on the secure disk image, be sure to eject the disk image. As long as it’s available on your desktop, anyone with access to your computer can use the documents on it.

Create a blank disk image for storage

You can create a blank disk image then add files to it later.

  1. Choose File > New > Blank Disk Image.

  2. Enter a name for the disk image, then choose where you want to save it.

  3. In the Name field, enter the name for the disk image (the name appears when you open the disk image).

  4. Click the Size pop-up menu, then choose the size of the disk image.

  5. To encrypt the disk image, click the Encryption pop-up menu, then choose an encryption option.

  6. Click the Partitions pop-up menu, then choose Single partition - Apple Partition Map.

  7. Click the Image Format pop-up menu, then choose sparse bundle disk image.

  8. Click Create.

To add files to the disk image, open it in the Finder, then drag files to its icon on the desktop.

Copy a CD-RW or DVD-RW disc

To burn a disc, you need an optical drive in your computer or one connected directly to your computer. You can’t burn a disc using a remote optical drive.

Disk Utility can’t copy discs that are copy-protected, including most commercial movie DVDs and audio CDs, and some software and data discs. To copy music from an audio CD to another CD, use iTunes, not Disk Utility.

  1. Insert the CD or DVD disc into the optical drive, then select the disc in the sidebar.

  2. Choose File > New > “Disk Image from disc name.”

  3. Enter a name for the disk image.

  4. Click the Image Format pop-up menu, then do one of the following:

    • Compressed: Compresses data, so the disk image is smaller than the original data. The disk image is read-only.

    • Read-only: The disk image can’t be written to, and is quicker to create and open.

  5. Click Save.

  6. After Disk Utility creates the disk image, eject the original CD or DVD.

  7. Select the disk image in the list at the left, then choose Images > Burn.

  8. When the Burn Disc dialog appears, insert a blank CD or DVD, then click Burn.

You can use the disk image to create as many duplicate discs as you need.

To access the data in a disk image, double-click it. It appears on your desktop, and you can add, remove, and edit files on it just as you would with a disk.

Protect a disk with a password
Resize a disk image
Convert a disk image
Last Modified: Feb 20, 2015
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