Carbon Copy Cloner restore limitations

TidBITS Talk
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I apologize to all here, and Mr. Bombich and his associates, in particular, for over-generalizing my data-restore experience as well as their advice. I have removed most of my comments, and will attempt to restate my experience more concisely.

Earlier this month, I suddenly realized I had gone from having three complete copies of my data, all on distinct physical devices, to only a CCC disk-image on a HFS+ spinner created with a CCC “Task” configuration almost a decade old. If I had been keeping up with the real implications of SIP, Sealed System Volumes, APFS, etc., I would have known this was at best, not the most reliable configuration under recent versions of macOS, particularly for the scenario of “your entire Mac from a backup, i.e. to a clean installation of macOS.”

When I tried to use CCC to restore the disk-image, it instructed me to use Migration Assistant. I could not find the disk-image with Migration Assistant. Somehow (panic had been creeping in a paragraph ago) I got CCC to partially restore the disk-image. Most third-party apps, Keychain and Safari passwords, etc. were not restored. Fortunately, I was able to reinstall my apps from *.dmgs, etc., and piece-by-piece put it all back together. Helpfully, the disk-image would still mount in the Finder. Ultimately, I believe none of my personal data was lost.

As Mr. Bombich has pointed out, there are numerous scenarios that do not require Migration Assistant to restore a CCC archive. Rob in CCC tech-support was very responsive, and helpful, advising me how to set-up my particular backup needs so this didn’t happen again. I, unfortunately, generalized his advice to other scenarios.

In my case, I used a badly out-dated backup configuration in a likely worst-case scenario (aka. user error - panic can do that).

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Isn’t that the purpose of a backup? I understand the apps with the multiple parts sometimes buried in the system, but how would you use the backup?

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That’s the impression I’ve gotten as well. You can restore your home directory and its documents, but restoring apps seems to be a problem, thanks to various changes to Apple’s security model.

I suspect the sandboxing system used to keep apps from interfering with each other has a lot to do with this.

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Which OS were you trying to restore with CCC?

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Monterey (10th character… ;-)

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This raises the question of SSD reliability, which was covered in these discussions a few years ago. My online research at the time suggested that SSDs need to be connected to a power source (i.e. a computer) every few months but others disputed this. In any case, it seems that a backup strategy should include a mix of SSDs and “spinners”. Also, for the latest macOS, a mix of Time Machine and CCC or similar.

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This raises the question of SSD reliability,

Well, not in this case. This was apparently the case of “errant” (or at least presumptive) software poking at the drives. Disk First Aid found the identical error on all of my SSD’s (more particularly, all my APSF drives) including the system volume which had not so coincidentally started having red-screen crashes. The red-screen crashes disappeared when the drives were reformatted. It is a long, exhausting story.

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Not really. Why? I have yet to see any evidence that HDDs are more reliable or age better than SSDs. In fact, pretty much any data I’ve seen says HDDs fail more often and earlier than SSDs.

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I agree that SSDs are more reliable for regular backups but in my experience they do fail. I simply want another technology available as a backup for backups.

I have a couple of HHDs that have sat in a crate for many years and they still work.

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I question this. I haven’t used CCC, but I do use SuperDuper! which works similarly. Your apps in Catalina and later are on the Data Volume. If you can restore that volume then all your apps come with it. I find it hard to believe that CCC is less capable than SD.

SuperDuper! also now recommends restoring by using the Migration Assistant, but that’s mostly due to inability to restore the System volume on Apple Silicon Macs. For example, the Intel iMac I’m typing this on was restored from a backup by cloning the Data volume back to the drive.

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I’ve not had the need to use Restore but if the application omission is correct it severely diminishes the usefulness of things like CCC and SuperDuper.

Personally I have a genuine disregard for Migration Assistant. In our use it’s proven several times to be unreliable and incomplete in its restores.

I agree that Apple is strangling the life out of usability. If not for compatibility issues I’d prefer to use Mountain Lion or Yosemite over any of the newer systems.

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Migration Assistant is rubbish, but it’s still on the more useful side of the spectrum of utility IMO. It has got better over the years, and especially recent years.

But ultimately, I do agree the loss of cloning functionality caused by the new arrangements for authenticated booting and system sealing have, sadly, been a net negative for the platform, with no real discernable user-facing gain. Migration Assistant can still read data volumes, and operating systems can still be installed on top of them, and that behaviour, imperfect as it is, does provide a close enough approximation to be useful, at least for now. Sort of like iOS backups, really. It’s just not a pinch on real cloning, because it’s not precise enough to do that and leaves bits out, as you say. This is just the new normal now. :(

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Well that certainly is a bummer with CCC. What good is it? If the clone is not really a clone.
I’m going back to S.Duper! I don’t expect it to restore the whole volume, as in the old days before 10.14 and below, but at least all of my own files, folders, apps and what not. Then it’s not really a backup- Now we have two meanings for the word ‘restore’. Grrr.
Migration Ass’t. does miss some stuff.

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While I haven’t tried a restore…a restore via CCC or Finder or whatever from a full clone of the data partition seems like it ought to work just fine.

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Anyone have thoughts on how this plays out with online backup such as Backblaze?

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That’s very much file-oriented backup, not really suitable for reproducible restores or cloning. Certainly you could back up some of the applications and support files to ease restores, but it’d be a more manual process than is usual with Migration Assistant restores from Time Machine or a data volume clone.

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I wonder what the scope of CCC’s restore limitations actually are.

If they have a problem restoring App Store purchases, that makes perfect sense to me, since the App Store sandboxes each app. Blindly restoring these app folders probably can’t create the system data necessary to reestablish the sandbox.

I assume that Migration Assistant, when restoring apps from the App Store, is probably doing what iOS does - re-download and install the app from the App Store, and then restore its (sandboxed) data from your backup.

But for other apps that are installed separately, including apps purchased separately (e.g. Microsoft Office, Filemaker and Photoshop) or for apps I compiled and installed manually (e.g. my installation of Emacs), I would be surprised if a simple file-restore didn’t work. Especially if the backup software is preserving metadata like resource forks, extended attributes and ACLs.

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FWIW, Migration Assistant pretty reliably screws up my MacPorts installation, not starting daemons properly, failing to restore the system accounts or map their names to their original UIDs resulting in hilarity when servers don’t have adequate permissions, and so on. It really is cookie cutter stuff.

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Hi folks, this is Mike, developer of CCC. I wanted to clear up some misunderstandings here because, lacking some context, it looks like this discussion has gone pretty sideways. You absolutely can restore applications from a CCC backup. My goodness, if you couldn’t restore apps from the backup, we’d have a pretty serious problem. There is a lot of context missing from Will’s statement here, and it really boils down to whether you’re “restoring some stuff” vs. “recovering your entire Mac to a clean installation of macOS”. Let’s pick this apart:

  • If you need to restore just an application, then the procedure is pretty straightforward. You can restore it via CCC, or simply drag and drop in the Finder. Both methods are supported.
  • If you need to restore all of your applications (but still just your applications), then same as above – you can use CCC for this, or drag and drop (I’d prefer CCC for a task this large).

Indeed, we document more than a dozen restore scenarios – you can restore from a CCC backup with CCC, we design the product for backup and restore.

Now, on to what Will was actually trying to do. If you’re trying to recover your entire Mac from a backup, i.e. to a clean installation of macOS, that is when we recommend using Migration Assistant to migrate data from your CCC backup. This recommendation does not vary among backup products now. Whenever you’re migrating user accounts to a clean installation of macOS, Migration Assistant is the only game in town. The user accounts have to be “adopted” by macOS, and only the macOS Installer or Migration Assistant can do that. If you wanted to choose to not migrate your apps, you could certainly restore them via CCC later, but personally I think that starts to make things more complicated.

Just to put a fine line under all of this – a "Standard CCC backup will include all of your data – that includes your user data, applications (app store too), system settings – everything about your Mac that is customized, we back up all of that. You can restore any of that content via CCC, but when you’re moving to a new Mac or restoring to a clean installation of macOS, you should use Migration Assistant to migrate all of your data/apps/system settings/etc to that clean installation of macOS.

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I wanted to touch on this specifically as well. There are no limitations regarding backing up nor restoring apps with CCC. It doesn’t matter if an app came from the App Store or elsewhere, CCC will back it up and can restore it too. The backup should be on an APFS-formatted volume though (and an APFS-formatted disk image would work fine, but we still don’t recommend disk images) so you’re retaining the space-savings of filesystem compression.

I assume that Migration Assistant, when restoring apps from the App Store, is probably doing what iOS does - re-download and install the app from the App Store, and then restore its (sandboxed) data from your backup.

Migration Assistant pulls the apps right off of the backup. No App Store connections are made until you log in to your restored account and then log in to your Apple ID. At that point all of the apps are already restored (typically, unless you chose to not migrate them).

I would be surprised if a simple file-restore didn’t work. Especially if the backup software is preserving metadata like resource forks, extended attributes and ACLs.

Precisely – CCC preserves all of that metadata, so restores from a standard CCC backup work just fine.

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