APFS Bug in macOS 10.15.5 Catalina Impacts the Creation of Bootable Backups

[MacRumors]

An Apple File System bug has been discovered in macOS 10.15.5 Catalina that can prevent users from making a bootable clone of their system drive, according to the creator of Carbon Copy Cloner.

In a blog post on Wednesday, software developer Mike Bombich explained that the CCC team had uncovered the issue in the Apple File System, or APFS, when attempting to create a bootable backup in a beta version of macOS 10.15.5.

According to Bombich, the bug prevents CCC from using its own file copier to establish an initial bootable backup of a macOS Catalina System volume. In technical terms:

The chflags() system call can no longer set the SF_FIRMLINK flag on a folder on an APFS volume. Rather than fail with an error code that we would have detected, it fails silently – it exits with a success exit status, but silently fails to set the special flag. That's a bug in the APFS filesystem implementation of chflags – if a system call doesn't do what you ask it to do, it's supposed to return an error code, not success.

We don't need to set many of these flags, nor set them frequently – just on the first backup of the macOS system volume. It happens to be essential to the functionality of an APFS volume group, though, so the failure to set these flags means that new full-system backups created on 10.15.5 and later won't be bootable, and it will appear as if none of your data is on the destination (to be clear, though, all of the data is backed up). Kind of the opposite of what we're trying to do here. It's hard to find kind words to express my feelings towards Apple right now.

Suffice it to say, though, I'm extremely disappointed that Apple would introduce this kind of bug in a dot-release OS update. We've seen 5 major updates to Catalina now, we should expect to see higher quality than this from an operating system.

On a positive note, existing backups created in macOS 10.15.4 and earlier are unaffected, the bug has no effect on CCC's ability to preserve data, nor does it affect the integrity of the filesystems on a startup disk or a backup disk. In short, the impact of this bug is limited to the initial creation of a bootable backup.

Any CCC users who established their backup on a previous version of Catalina already has functional firmlinks on their bootable volume and CCC will continue to update that volume just fine. Meanwhile, users wanting to create a new backup of a 10.15.5 volume to an empty disk should replace their copy of CCC with the CCC 5.1.18 beta, then follow these steps on launching the app.

1. Click the X button in the Destination selector box to clear the destination selection.
2. Click on the Destination selector and reselect the destination volume.

CCC will then guide users through the procedure of creating a bootable backup, or a Data-only backup instead. The new functionality uses Apple's Software Restore (ASR) utility.

Bombich has notified Apple of the bug, but he ends his blog post by entertaining the possibility that it is a security fix to prevent third-parties from creating firmlinks. If so, he argues, "this is far worse than a bug," since the system currently reports a success when it should report a failure, not to mention that Apple's lack of documentation on the change is hostile to third-party developers who rely on documented functionality.

Article Link: APFS Bug in macOS 10.15.5 Catalina Impacts the Creation of Bootable Backups

 

[thisisnotmyname]

so outside of people trying to steal Apple IP to load newer MacOS versions on older systems or create hack-instoshes it must be a very small community of people that's affected by this.

 

[newdeal]

I just want them to fix the bug that makes the mail app pop up randomly when I am using gmail (works fine with icloud). Oh and maybe reopen some stores in Canada so I can get this damn keyboard replaced (S key popping off on 2017 mbp non touchbar)

 

[weup togo]

so outside of people trying to steal Apple IP to load newer MacOS versions on older systems or create hack-instoshes it must be a very small community of people that's affected by this.

this is so offensively dumb, I can’t find the words

 

[star-affinity]

A bug in Catalina? No way! Apple makes both the hardware and the software so things work flawle… 🤡

 

[philosopherdog]

This is terrible. I’m assuming this also affects Superduper too? Catalina really is disappointing. I’m also having to work around major wake cycle crashes with external displays.

 

[baryon]

Good thing Apple has beta testing to iron out issues like this before they get released to the public!

 

[ikir]

A bug in Catalina? No way! Apple makes both the hardware and the software so things work flawle… 🤡

Just use Windows for one week and macOS will be perfect again. Believe me I’m an IT and half week I’m working for a big company with everything Microsoft related. HELL ON EARTH.

 

[skippermonkey]

It's the OS that just keeps on giving.

 

[superiska123]

Just use Windows for one week and macOS will be perfect again. Believe me I’m an IT and half week I’m working for a big company with everything Microsoft related. HELL ON EARTH.

This is so accurate! Catalina is a truly terrible release, but I seriously cannot comprehend the praise Microsoft gets for Windows 10... In my experience as a software developer, macOS is still miles ahead of Windows.

 

[Moshe1010]

why would anybody bother backing up MacOS if everything is on the cloud these days?

 

[wordsworth]

I just want them to fix the bug that makes the mail app pop up randomly when I am using gmail (works fine with icloud). Oh and maybe reopen some stores in Canada so I can get this damn keyboard replaced (S key popping off on 2017 mbp non touchbar)

I was under the impression that this was a Google problem. Began happening to me immediately after I signed up to Gmail.

I am increasingly thinking that Apple's software is not as robust as it once was and my own experience would seem to corroborate that. My MacBook Air crashed the other day. Off. Black screen. No power. It was plugged into the mains supply but the battery should have kicked in if that was an issue, and it wasn't an issue. I had to reboot. It's happened before a couple of times, too. I feel like it's possibly to do with Mojave. Never happened to me in the Sierras or El Capitan.

A friend was designing an app for iOS. Said it was a nightmare in a variety of ways. I respect his expertise and opinion. His take on it is that the hardware is good but the software can be poor.

As others have said on this forum, maybe Apple ought to take its time and not pump out OS iterations so relentlessly.

 

[MakeAppleAwesomeAgain]

I downgraded to Mojave on my Macbook and never upgraded my iMac. I couldn't be happier, it seems I'm on Mojave for a long, long time.

 

[jclardy]

Aah..could we please just get a stable release at WWDC. No new features. Just fix what is there.

My 16” MBP has had wonderful sleep issues (every time I put it to sleep for more than 4 hours it’ll reboot randomly in that period.) Amazing machine otherwise...but sleep was one of the most solid features in every mac laptop i’ve owned since my first plastic Intel Macbook. And in 2020 somehow they’ve screwed that up.

 

[4492865]

Apple is stretched too thin — no longer focused on a few key products and deliver them well. They’ve decided to compete in so many areas and their core products are now suffering because of it. iOS 13 has been a cluster**** right from the beginning and just shows that their QC processes for software are below par.

 

[bchah]

I don't comment often, but when I do... it is to confirm that if Mike Bombich is saying this is a problem, then this is a problem.

 

[dogslobber]

This bug is terrible for missing. How do you release a product and not regression test this type of thing? It's so elementary that any QA test plan should have coverage of these areas. Grade F, Apple.

 

[Gutwrench]

Ok, so an error flag wasn’t set properly.

This reminds me of an old saying, “Sometimes even the monkey falls out of the tree.”

Fix it and move on.

 

[nova motum]

Such a mistake must not happen in a public subrelease of macOS, especially as there had been 5 beta versions of 10.15.5 where the community could have detected the bug...
- I wonder whether the SF_FIRMLINK flag is being set correctly when using root permissions (just for a technical understanding)

Besides this, regarding APFS (which I still believe is really genius)

- I wonder why even Apple within 4 years has not managed it to create disk images of single APFS subvolumes within their containers - yet, only the complete container with all sub volumes in it can be transformed into an image

- And I wonder why Apple still sticks with HFS cs instead of APFS for Time Machine - there would be a much higher performance and storage size advantages, too....

 

[mookc1]

I don't comment often, but when I do... it is to confirm that if Mike Bombich is saying this is a problem, then this is a problem.

Agree 100%.

 

[swingerofbirch]

Ok, so an error flag wasn’t set properly.

This reminds me of an old saying, “Sometimes even the monkey falls out of the tree.”

Fix it and move on.

The APFS roll out has been a nightmare on the Mac from the beginning. Apple provided almost no documentation to developers.

 

[MacDevil7334]

Wow what is going on with Apple’s software QC process these days? I have never sat out an entire MacOS release before. I thought 10.15.5 would finally be stable enough to get me to upgrade from Mojave. But apparently not. And iOS 13 still has bugs that have been present since the first beta (looking at you, Mail). Something is really broken over at Apple right now.

 

[TMRJIJ]

It doesn’t seem like Public Betas are helping Apple. Either nobody is submitting these bugs or their QC is stretching to thin.

 

[imnotthewalrus]

Sigh. I use CCC on a regular basis. Kudos to Bombich ad the CCC team not only for finding the bug, but creating a temporary solution.

 

[dspdoc]

And in other news; getting massive kernel panics on a brand new Mac Pro running 10.15.5 here. What are you even doing, Apple?!