macOS 26.4 Beta: Problems Mounting HFS+ Volumes

But sure, these guys are going to execute a Snow Leopard update. Okay.

On the one hand, I just don’t understand, in terms of release cycles, why this — a sudden regression in a minor release — keeps happening. Is their test suite so small, their code base so brittle, their willingness to cherry-pick changes from main so large? Why does 26.4 suddenly change the HFS+ stack?

OTOH, Apple has it in the beta release notes, so that may suggest 1) they were indeed making a change to the disk subsystem, knowing the risk, 2) they intend to fix this by final.

By far the most bemusing thing about this is that it is clear that Apple was aware that there was an issue with the HFS+ filesystem module, but the workaround doesn’t work in many cases.

It is clear from the rpath error that fsck_hfs is some kind of internal debug build, but it makes you wonder how exactly they assemble the OS. I mean, how did that get pulled in, but the other binaries are okay? mount_hfs is fine.

Apple can't even get it right in the release notes. The bug impacts HFS+ volumes, not HFS volumes. Support for HFS volumes was removed in 10.15.

I wonder if they're doing something silly like rewriting fsck_hfs in Swift. You know, since the OS is mostly bug-free and polished.

Maybe this is the special Apple experience: not being able to use external media. Did they pull this build?

I get this same message on an HFS+ drive in Sequoia. Is it actually true on Sequoia or is it also inaccurate there?

@Sören They moved to changing underlying frameworks in .4 few years ago. In Sonoma I had issue when they broke compression value for HEIC images. It partially got fixed in 14.5 release (1.0 compression value remained broken for API but not for Preview). https://developer.apple.com/forums/thread/748300

It's this because some aren't used to having a shit ton of backwards comp to worry about? A delayed cultural mine planted by osx and then the move to new architecture.

@Manx, I don’t think fsck_hfs is broken on any Sequoia build, so that is something you should take a look at.

If you open Terminal, run fsck_hfs and it doesn’t just vomit a very verbose error, then your HFS+ drive probably has actual issues.

"I have 7 (seven!) external drives that I currently can’t use 🙄"

On a beta system?

"Finally figured out how to properly mount my external HFS drives under macOS 26.4b1!"

I probably wouldn't mount HFS+ volumes on a beta system that has known issues with HFS+ volumes, unless I didn't mind losing all the data on these volumes.

I thought I read where it was best to have external drives formatted as APFS, instead of HFS+, when using Monterrey and forward. Is that not the case? or am I not reading this correctly?

I'm glad to see DiskWarrior getting mentioned again. That wonderful piece of software is one of the reasons I don't want to transition all of my drives to APFS, because APFS doesn't have a magical cure-all.

It's also distressing but totally expected to see these kinds of changes happening in a minor point release. Why is Apple changing major, critical parts of their already bug-ridden OS in what are supposed to be minor updates whose major purpose is ostensibly to fix bugs?

@billyok gets it exactly right. They're not going to pull off a "Snow Leopard" release even if they try. This is yet another indicator of the dysfunction plaguing Apple's software development.

@Clay APFS offers some advantages like snapshots, but for spinning hard drives the performance remains terrible. I think that’s fundamental to the design.

Speaking of DiskWarrior, there was a minor update recently from version 5.3.1 to 5.3.2 to better work under Tahoe's Liquid Glass UI. Still no APFS support.

While I do miss DiskWarrior, and still use HFS+J for spinning drives because APFS sucks on them, the benefits of APFS on SSD are substantial, particularly copy-on-write. It makes it trivial to protect previous versions of files and folders, even very large ones such as Photos libraries or Outlook databases, because you can duplicate them first before you do something to them, but with their copies only taking up as much space as the changes you make. That's gold. And snapshots and additional volumes without partitioning are also very helpful.

(It's a problem for backup via any means other than Time Machine or block-level copying, though, since the copies effectively "expand" at the destination. CCC does at least have partial support for keeping the copied file as a pointer/clone, if it has had no changes to it.)

Not having a robust disk repair utility is a bummer, but, on the other hand, it makes me take backups more seriously, so there's that. And I encounter corrupted APFS volumes significantly less often than HFS+/J volumes -- it's usually a media falure as opposed to a file system problem.

Apple has appeared to have fixed this with the 2nd 26.4 Developer Beta today.

Has this been verified by anyone? Release notes still state:

Known Issues:

HFS external media might fail to mount automatically. (168672160)

Workaround: For macOS only, use CLI tool diskutil mount to attach the relevant disk device.

Asking before I go through with an install, as this issue warrants my immediate action if actually addressed.

Thanks!