How to clone an APFS system disk with Disk Utility.

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How to clone an APFS system disk with Disk Utility.

It's been now a while I've been doing tests with High Sierra (10.13.5 recently). And I still can't envision moving to it with an SSD system disk, as I haven't yet been able to figure a way to clone an APFS system disk with Disk Utility.

Using Disk Utility to clone an APFS data disk works fine, without any issue. But when trying to clone an APFS system disk, the works progresses smoothly until the last step. Then, the target volume inversion fails (by the way, what on Earth is this "target volume inversion" and what is it needed for?). DU informs me that "APFS inverter failed to invert the volume - Invalid argument" and then "OSStatus error 22". Then I'm left with a useless target volume, only good to be reformatted. For information, the target disk is a newly created APFS partition on an external Thunderbolt/USB3 rotational disk (most of the other partitions on this disk are still HFS+), if this is relevant to the issue.

There's no way I'm ready to do production work on a system where I can't clone the system disk and obtain a verified bootable copy of my system as a fallback system disk in case of a problem with the internal disk.

So the question is: "How can one clone an APFS system disk with DU and obtain a bootable clone"?

I'm aware that some third party backup softwares say they can create such a clone (I do have CCC V5, but haven't yet tested this feature with APFS system disks, it's still on my "to do" list), but even CCC does not perform a complete "Verify" pass on its target volume. At best, when told to, it verifies checksums on previously saved files, which, while good, is still not enough.

Denis Maillard.

MacBook Pro, macOS High Sierra (10.13.5), 8 GB Memory

Posted on Jun 4, 2018 1:34 AM

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Answer 1

Top-ranking reply

John Lockwood

Level 6

13,691 points

Jun 5, 2018 1:50 AM in response to DenisMaillard

I think you are making life for yourself too hard.

CCC is the defacto choice for doing this. CCC is written by Mike Bombich a former Apple employee. You have probably seen it but incase not - Everything you need to know about Carbon Copy Cloner and APFS | Carbon Copy Cloner | Bombich Software

The only other option is SuperDuper! from ShirtPocket - https://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html

Beyond these you get into more esoteric territory. One possible approach is to use the commandline tool dd to do a block level copy of the entire source drive to an empty destination drive, ideally both would be the same size but the destination could be bigger. You do not want to just dd the macOS boot partition because you also need to copy the other partitions e.g. the EFI one and the RecoveryHD one, so instead of a source/destination like /dev/disk0s2 you would do the entire /dev/disk0

There are some hardware devices which do a similar thing to dd in that they block copy entire drives.

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Answer 2

Jun 5, 2018 1:38 PM in response to John Lockwood

Thank you for the reply, John. However, please, take note that I am talking of the need to have a VERIFIED backup clone of the system disk. This is simply a question of survival for someone who depends on her/his computer for important or even vital matters. CCC does a good job but does not (yet?) provide any option to verify the integrity of the saved data. DU does it for HFS+ system disks, even if it is tedious, but one should have a realistic approach to the problem: short of implementing RELIABLE disk shadowing, an offline backup is the only way to create a verified clone. What I am saying is that, for Apple to force users to have APFS system disks without providing a way to create verified clones of these disks, is simply a way to send them to their doom sooner or later.

Given that Time Machine is, at best, a form of Russian roulette (on the two occasions where I tried to use it in actual need, it once provided me with a non bootable system disk and, on the second occasion, where I asked the migration assistant to get the configuration from a freshly created Time Machine data set, it missed several HUNDREDS files; in both cases, I was only saved because I'm a firm believer in belt-and-suspenders policy and had other types of backups available; this, while the Time Machine save operations had never given a single error message when doing their work), Apple owes it to its installed base to provide a reliable way to save their systems. Time Machine is NOT a backup utility but an unnecessarily complicated copy utility, prone to errors that should NEVER happen with a backup tool. APFS systems disks simply NEED to be RELIABLY and VERIFIABLY cloned. I'm waiting for the tool to do this, or, if it already exists, for a clear user's guide.

Denis Maillard.

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How to clone an APFS system disk with Disk Utility.

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