Carbon Copy Cloner
The long-standing answer to “I want a second disk that is this disk”, now with snapshots and proper scheduling.
What it does
CCC copies a volume to another volume on a schedule, keeping the destination an exact match of the source and optionally holding APFS snapshots on both sides, so a file deleted three weeks ago is still retrievable. Task-level filters, pre- and post-flight scripts, email on failure, and a task history that says what actually ran.
Its Legacy Bootable Copy Assistant is the part people come for, and the part with the caveats below.
Notes
- The macOS system volume can only be duplicated by Apple’s own
asr, which copies whole volume groups and nothing smaller. Every tool in this category is subject to that, not just this one. - On Apple Silicon a bootable copy is unreliable on USB enclosures and more consistent over Thunderbolt. Treat a bootable clone as a convenience and your data backup as the actual plan.
- An Apple Silicon Mac will not start from an external disk at all if its internal storage has failed: a stub of macOS on the internal drive has to validate the external one first.
Alternative to
| Alternative | Type | Trade-off |
|---|---|---|
| Time Machine | Built in | Already there and versioned, but no clone and little control over scheduling |
| SuperDuper! | Freemium | Narrower and cheaper; no snapshot retention |
| ChronoSync | Paid | Aimed at folder-level sync rules rather than whole volumes |
| Macrium Reflect | Paid | The Windows equivalent; nothing to install on a Mac |
| restic | Open source | Versioned and cheap to store, but never bootable |
Install
brew install --cask carbon-copy-clonerLicensed per household, one-off, with paid major upgrades. The trial is fully functional.