macOS 15 Sequoia on Unsupported Macs Thread

[amaze1499]

Is it possible to treat macOS like Linux, or another Unix system in terms of fstab, and stop all my Volumes from auto mounting? E.g. when booting into Monterey, can I stop the "Macintosh HD" volume with Sequoia from automatically mounting, and vise versa ?

Apple’s Disk Arbitration daemon overrides manual mounts. Since macOS Catalina the “split system volume” structure was introduced: System Volume (read-only) Data Volume (writable)

These are “sealed” system volumes that automatically mount on boot and are required for the OS to function.
So while you can block mounting of external or non-system volumes via /etc/fstab or diskutil,
you cannot prevent the active macOS’s own system volume from mounting, it’s part of the boot process.

When you boot into Monterey, you can stop the “Macintosh HD” (Sequoia) volume from auto-mounting by editing /etc/fstab. However you will need to add the UUID in order for that to work. But you need to know what you are doing, if not you could break something essential.

If you are bothered by the icons on the desktop only, you might consider to turn them off in Finder settings.

 

[Bigwaff]

Is it possible to treat macOS like Linux, or another Unix system in terms of fstab, and stop all my Volumes from auto mounting? E.g. when booting into Monterey, can I stop the "Macintosh HD" volume with Sequoia from automatically mounting, and vise versa ?

You're probably better served by creating an Automator script to unmount the offending volume. Add to your Login Items.

 

[MacinMan]

Apple’s Disk Arbitration daemon overrides manual mounts. Since macOS Catalina the “split system volume” structure was introduced: System Volume (read-only) Data Volume (writable)

These are “sealed” system volumes that automatically mount on boot and are required for the OS to function.
So while you can block mounting of external or non-system volumes via /etc/fstab or diskutil,
you cannot prevent the active macOS’s own system volume from mounting, it’s part of the boot process.

When you boot into Monterey, you can stop the “Macintosh HD” (Sequoia) volume from auto-mounting by editing /etc/fstab. However you will need to add the UUID in order for that to work. But you need to know what you are doing, if not you could break something essential.

If you are bothered by the icons on the desktop only, you might consider to turn them off in Finder settings.

Oh, It's not an issue with icons. I have one or two apps that complain if multiple versions are detected e.g. one on the active system drive and the other on the inactive system drive. I do know how to manage fstab in Linux, but Apple likes to break, or change the standard way of doing things, so that's why I was curious. So my plan was, when booting from the "Monterey HD", "Macintosh HD" wouldn't auto mount since it's not needed, and vise versa, when booting "Macintosh HD", "Monterey HD" wouldn't mount, as it wouldn't 't be needed, and it would prevent duplicates of being found of things that don't like that.

 

[amaze1499]

Oh, It's not an issue with icons. I have one or two apps that complain if multiple versions are detected e.g. one on the active system drive and the other on the inactive system drive. I do know how to manage fstab in Linux, but Apple likes to break, or change the standard way of doing things, so that's why I was curious. So my plan was, when booting from the "Monterey HD", "Macintosh HD" wouldn't auto mount since it's not needed, and vise versa, when booting "Macintosh HD", "Monterey HD" wouldn't mount, as it wouldn't 't be needed, and it would prevent duplicates of being found of things that don't like that.

I'd stick with @Bigwaff 's suggestion so.

 

[MacinMan]

I'd stick with @Bigwaff 's suggestion so.

OK, I'll look into that, I've used cron before but not automator.

 

[macpro_mid2014]

OK, I'll look into that, I've used cron before but not automator.

I use two different Volumes in my MBP11,2, each one of them with a version of macOS and I always enable FileVault on them.
So, every time I boot say Sequoia, macOS asks for the password to mount the Big Sur volume. If I close the pop-up window and don't enter the password, the volume is not mounted. But there is this annoyance of having to manually close the pop-up window asking to enter the password every time you boot the computer.

 

[Tratkazir_the_1st]

@MacinMan
Probably you need to dig about "no_automount" (or similar?) filesystem attribute, if APFS supports it. (It works with Linux filesystems.)