Thursday, June 6, 2019

Backing Up macOS 10.15 Beta

Dave Nanian:

FYI, anyone using Catalina - SuperDuper does NOT work properly. Please don’t rely on it under Catalina until we’ve managed to figure out why, or if it’s possible.

Mike Bombich:

In the Finder you’ll only see one volume that represents your startup disk and it will appear as if everything is on that single volume. In reality, the startup disk that you see in the Finder is the read-only system volume and doesn’t have any of your data on it; the “Data” volume is separate and hidden.


Allow me to be the first to say it: stick a fork in it, HFS is done. HFS simply won’t work for making a backup of a Catalina system volume, so in the near future, we’re going to drop support for backing up macOS (Catalina and later) to HFS+ formatted volumes.

Dave Nanian:

Anyone out there able to create a disk group under Catalina with diskutil? I keep getting ( (disk3s1 role S):

diskutil ap createVolume disk3 APFS "MacBook Backup-Data" -role D -groupWith disk3s1
Error: -69624: Unable to add a new APFS Volume to an APFS Container

The answer, if anyone cares, is that you have to add a system volume to a data volume. You can’t add a data volume to a system volume. Because…reasons?


Update (2019-07-10): John Martellaro:

In this timely post-WWDC show, Mike [Bombich] joins me to explain the structure of APFS drives and the new read-only System files in macOS Catalina. He explained new features of volumes in macOS 10.15, especially how the System is isolated from the Data volume (which contains /Users). He also explained the new firmlinks that tie these two volumes together, making them appear as one. Finally, Mike explained how Carbon Copy Cloner external drives can no longer be HFS+ in Catalina but must become APFS.

Dave Nanian (tweet):

This new arrangement presents those of us who are creating bootable backups with—and I’ll employ my mildest language here; the forehead-shaped dents in my desk tell a different story—something of a challenge: we can’t write to a system volume (again, it’s read-only) and we can’t create firmlinks. are we going to create backups? How are we going to restore them?


These changes will be as extensive as the ones we had to make when APFS was introduced, if not more so. We have to take a quite different approach to copying, make understandable errors appear when the underlying system APIs provide no details, and we have to depend on a bunch of new, unfinished, un-and-under-documented things to make any of this work at all.


So far, while we’ve validated the general approach, we’ve run into a lot of problems around the edges. Catalina’s file system and tools are rife with bugs. Every time we head down one path, we’re confronted with unexpected behavior, undocumented tools, crashes and failures.

7 Comments RSS · Twitter

Does macOS BETA 1 version 10.15 (19A471t) Catalina has a new version of Time Machine? Which one? Does it support APFS. I will appreciate if you could do the following test. What happens if you boot from Catalina (without Time Machine disk connected) and connect an external SSD disk formatted as APFS? Does it prompt to format it as HFS+ to be used as Time Machine disk? That will tell if the new Time Machine in Catalina supports APFS or still requires HFS+. Thanks.

Donald Perreault

I have successfully backed up using Time Machine on APFS formatted drive in Catalina. I have not tried recovering anything from the TM backup but if I open Time Machine it does launch and allow me to go back in time. Hopefully this is helpful.

Hi Donald, that is great. Are you sure that the Time Machine disk is formatter as APFS (showing that instead of HFS+ in Disk Utility)? Sorry to ask again, but other people are saying that macOS 10.15 Catalina BETA 1 (19A471t) does not support APFS disks as Time Machine, but only HFS+. For instance:

Apple unveils new macOS update "Catalina"
I'm going to punch something if Time Machine still uses HFS+.

At least on this first beta, Time Macine still prompts me to format my APFS drives to use as Time Machine drives. Sorry :(


You can open Disk Utility select time machine disk or volume and see on the right window or click the "i" to see if it says APFS or Mac OS Extended (Journaled) which is HFS+. Thanks again.

In case it was not clear above, what I asked for was NOT if Catalina installs in APFS disks which I know is a requirement,
if Time Machine in such macOS can use APFS disks or still requires older HFS+ which are Mac OS Extended (Journaled).

[…] macOS 10.15 Catalina Preview (my post, Catalyst, backup) […]

[…] Backing Up macOS 10.15 Beta […]

Leave a Comment