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:
Working with APFS Volume Groups
For a data-only backup, CCC copies the entire Data volume within that APFS volume group. The System volume, which contains only about 15GB 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.
Creating a data-only backup
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
Installing macOS onto a data-only backup
If your data-only backup resides on a non-encrypted APFS volume, you can install macOS onto the backup disk to make it bootable.
Intel-based Macs
- Download and open the macOS Installer: [Catalina] [Big Sur]
- 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
Apple Silicon Macs
- Shut down your Mac, then power it on while holding down the Power button until the startup options are loaded
- Click on the Options button, then click the Continue button
- When Recovery has loaded, click on the WiFi option and join a WiFi network if your Mac is not connected to a wired network
- Choose the option to Reinstall macOS Big Sur
- Proceed to install macOS onto your backup disk
Migrating data from a CCC backup using Migration Assistant
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 (Intel Macs) or the Power button (Apple Silicon Macs) 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 backup volume