A data-only backup is a complete backup of all of your data, settings, and applications
In some cases CCC will create a data-only backup of a macOS startup disk. If you're unfamiliar with the APFS Volume Group concept that Apple introduced in macOS Catalina, you can learn more about it here:
For a data-only backup, CCC copies the entire Data volume within that APFS volume group. The System volume, which contains only about 12GB of read-only system files that are installed by the macOS Installer, will not be copied. A data-only backup is not bootable, however the backup can be made bootable by installing macOS onto it, or you can use the data-only backup as a source to Migration Assistant.
In some cases CCC will configure your task for a data-only backup automatically. You can perform the following steps to manually configure a data-only backup.
- If you would ultimately like to make the backup bootable, erase your destination volume as APFS in Disk Utility
- Click the Show Sidebar button in CCC's toolbar
- Drag the Macintosh HD - Data volume from CCC's sidebar onto the Source selector
- Click on the Destination selector and choose your destination
If your data-only backup resides on a non-encrypted APFS volume, you can install macOS onto the backup disk to make it bootable.
- Download and open the macOS Installer: [Catalina]
- When prompted to select a disk, click the Show All Disks... button and select your backup disk
- Proceed to install macOS onto your backup disk
You can use Migration Assistant to migrate data from your CCC backup to a clean installation of macOS. For example, if your startup disk is corrupted or had to be replaced, you could follow these steps to reinstall macOS and restore your data:
- Boot your Mac while holding down Command+R to boot into Recovery Mode
- Use Disk Utility to erase your Mac's (new) internal disk as APFS (see this Kbase article for additional guidance)
- Quit Disk Utility
- Select the Reinstall macOS option and proceed to install macOS onto your new disk
- When macOS boots for the first time on your new disk, you will be prompted to migrate data — accept the migration offer
- When prompted to select a source for the migration, select your CCC data-only backup volume
If you have established a valid, bootable backup volume (e.g. by installing macOS onto your data-only backup), you can reconfigure your CCC task to update the System volume on the destination (as necessary). Likewise, if you created a data-only backup task in error, you can reconfigure the task for a normal, bootable backup with these steps:
- Click the X button in the Source selector to remove the current source selection
- Click on the Source selector and choose your Mac's startup disk as the source to the task
CCC will determine if a bootable clone configuration is possible with the current source and destination. If the configuration is accepted, save the task and you're all set. If the configuration requires changes, CCC will present the options to you.
Note: This configuration will not be an option for Big Sur users until Apple resolves a problem with its proprietary APFS replication utility on that OS.