Cloning Disks

Cloning a Disk

The disk cloning tool will delete all files on the destination volume if you clone to this disk for the first time. Deleting files can take some time. To save your time, you can erase the destination volume using the Disk Utility application beforehand. There is no need to erase the destination disk if you run cloning with the same source and destination disks again because most of the files can be reused.

  1. Select a volume that you want to duplicate in the From drop-down list.
    The volume must be formatted as APFS or Mac OS Extended and contain macOS installed if you want your clone drive to be bootable.
  2. Select a volume where the duplicate will be saved in the To drop-down list.
    Make sure that there is enough space. Note that the existing content of the destination volume will be erased. If the formatting of the destination is other than APFS or Mac OS Extended, you have to change its formatting or choose another disk. You can also use a disk image as the destination.
  3. Set up the disk cloning properties.
  4. Exclude files or folders if necessary. To do this, deselect check boxes next to the file or folder names. It is not recommended to exclude anything outside your Home folder.
  5. Click the Start button.

Notice that on macOS 10.15 and later, there are two commands for cloning in the main menu. The Start Clean Cloning command should be used for the first time (e.g., when you clone to an empty destination). This command formats the destination volume and replicates your disk volume with help of the asr (Apple Software Restore) utility.

The second command Start Cloning is used to update a previously created clone. On systems earlier than macOS 10.15, this command is used for both the initial and repeated cloning.

Creating a Disk Image

A disk image can be used as the destination volume. The To drop-down menu lets you choose an existing disk image or create a new one.

Drop-down menu with cloning destination options.

In order to create a disk image, select Create Disk Image… in the drop-down menu. Select location and type in the file name and disk image name. Then set up the maximum size of the disk image and format.