Making bootable backups on Big Sur with Carbon Copy Cloner

In addition to using Time Machine to backup to my Synology, I’m also trying to make a bootable backup of Big Sur to an external SSD using CCC.

In case the SSD in my MacMini physically dies, I would like to still be able to use the system until I send it in for repair. Having a bootable backup seems like the logical thing to do.

I then found this on the CCC website, which is disturbing.

" Copying Apple’s system is now an Apple-proprietary endeavor; we can only offer “best effort” support for making an external bootable device on macOS Big Sur. We also do not generally recommend that users attempt to make their backups bootable — you can restore all of your documents, compatible applications, and settings from a standard CCC backup without the extra effort involved in establishing and maintaining a bootable device."

Do you make bootable backups of your Macs? If so, how?

I made a bootable backup of my M1 Air the other day using CCC and it worked absolutely fine.

The issue, as far as my quick review of all that useful documentation, is that they can’t provide all the bells and whistles of a backup that is fully under their control.
If you simply want something that you can switch to if something dies, it’s fine to use as far as I could tell and the main “problem” would be any OS updates released since you started the backup won’t be installed yet. I’m a bit hazy on that…

Not any more. Just data backups from my M1 MacBook Air via Time Machine and Carbon Copy Cloner.

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I’m still doing bootable backups of my Macs, but I have accepted that this probably isn’t a process I’ll be able to continue over the long term. I’ll still keep making non-bootable clone backups though.


Can Carbon Copy Cloner do the same things Time Machine does?

I do weekly Carbon Copy Cloner backups with a revolving set of disk drives that are plugged in only during each backup. But CCC has a scheduling facility and I understand that some people leave a disk drive plugged in all the time and run scheduled backups to it, kind of like Time Machine. But Time Machine is so much easier to set up. You simply plug in a drive and say YES when macOS asks if you want to use it for Time Machine. And I’m not aware that CCC could make hourly snapshots if backup media was unavailable or that CCC could cull the backups to re-use drive space the way that Time Machine does.

Also Time Machine supports file versioning in a way that Carbon Copy Cloner does not.

And it must be said that I trust my Carbon Copy Cloner backups more. Time Machine is great when it works. But, as others have noted in this forum, it too often gives up on an existing backup disk and says that the whole thing must be started over again from scratch.


I find CCC scheduling much more convenient. You can have backups run when a drive is plugged in - great for offsite backups. I don’t need hourly backups so I have them run at a time I prefer.

CCC supports snapshots on APFS volumes. For the boot drive, snapshots must be manually enabled. They don’t require the destination drive to be connected for the snapshots to be made. reference

For non-APFS non-snapshot volumes, CCC has SafetyNet, which can retain copies of files that are replaced on the destination, giving you some history of versions. It also has a setting to selectively remove old versions when the drive fills. This works pretty well, but I’ve had to help it in the past by deleting the SafetyNet folder on a full drive. reference

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Some of the features I mentioned may be specific to CCC 6, which I didn’t realize is out now.

I have two bootable drives using CCC. With Big Sur Apple made a change to what can be written to the system volume of the drive. Basically once the system is installed, nothing else can modify that volume. That’s why there are now two volumes, one with just the name of the drive, and the other with “ - Data” appended to it which is where your apps and files live.

CCC is able to create a FRESH clone of a drive, including the system volume. But it can no longer modify that volume on the backup drive once it’s created. It can only modify the “ - Data” volume. What does this mean in terms of practicality? You can absolutely create and “maintain” a bootable backup. What you cannot expect, is that any future OS UPDATES be applied to the backup drive (because they’re part of the OS volume, not the Data volume). But any changes made to the apps, documents etc. would be backed up since they reside on the Data volume.

I just had to boot from a backup drive yesterday, and it was exactly the same except running an older version of Big Sur. I can always boot from my backup drives and install the OS updates to them if I want to, but for a backup drive it’s not a big deal to me.

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