Can't delete MacOS Install Data folder from hard drive. OS 26.2

First thing......do you have a good backup of your system? If not, that should be your first order of business since you may need it.

Second, you can try deleting the "macOS Install Data" folder while booted into recovery mode. If that data is indeed located on the "Data" volume, then it should be possible to delete it, however, if it is actually located on the signed & sealed read-only system volume, then it will break the seal on it & prevent you from booting normally. Unfortunately macOS does a lot of behind the scenes magic to make the system volume & Data volume appear as one, so it can be impossible to tell where this item is physically located.

How to start up from macOS Recovery - Apple Support

You may need to end up performing a clean install of macOS (requires erasing the disk) followed by restoring from a backup. While the Erase All Content & Settings should work, you may need to use the Disk Utility option to erase the disk if that folder is actually located on the sealed system volume rather than the "Data" volume.

Use Disk Utility to erase a Mac with Apple silicon - Apple Support

Use Disk Utility to erase an Intel-based Mac - Apple Support

farrelli wrote:

Thanks. However, I found a number of replies elsewhere here that this usually results from a past upgrade that didn't finish correctly. They all say that it's safe to remove. I mean, it's from 2024, so how relevant could it be now that I'm on 26.2?

I have a 1TB drive but I am getting tight and never have enough time to figure out what I could offload, so I'm looking to save where I can. This is over 3TB of apparently wasted space.

Thanks again.

You are welcome though you also mentioned " on my HD and it's taking up over 3GB." Not quit the same

If we understand the situation correctly " I am getting tight "

Reducing Mount Point System/Volume/Data is a common question. 

1 -  System data taking too much in MacOS Sono… - Apple Community

2 - Time Machine Local Snapshot won't delete - Apple Community

3 - Over 60% storage blocked by System Data - Apple Community

How to free up ‘System Data’ and other storage on your Mac from a fellow colleague  @ neuroanatomist

Use another application to see where space is being used  Storeograph  on the Apple Apps Store 

Suggest getting an External SSD Drive and start moving your Pictures, Videos, Music and any other large files you have control over, OFF the Internal drive and Onto the External

There are  two effective ways to remedy this issue:

Quick Fix Actions:

For Apple Silicon computers, use Disk Utility to erase a Mac.

For Apple Intel computers, use Disk Utility to erase an Intel-based Mac, then reinstall macOS.

Always make a Time Machine backup before proceeding.

   Migrate only the user account, not the entire system.

   Reinstall only the necessary applications from the Apple App Store or directly from the developers.

Note - On Apple Silicon and newer computers. The SSD Drive and the Unified RAM are Soldered to the Logicboard and can not be upgraded.

By virtue of mount point of System as in /System/Volumes/Data

It can not be removed

Lives on the Data volume (normal for modern macOS with ( sealed system volume)

The macOS operating system resides in a sealed and read-only volume that can’t be opened by users or third-party applications.

Why does the user believe this specific 3GB is causing problems ?

Does the computer behave oddly or does not work at all ?

Is the computer giving a warning that computer is running out of Free Space

On my recently update M4 machine to Tahoe 26.2

disk3s5 - Data [APFS Virtual drive]

        Filesystem: APFS

        Mount point: /System/Volumes/Data

        Encrypted

        Used: 39.75 GB

        Shared values

            Size: 494.38 GB

            Free: 432.41 GB

            Available: 454.45 GB

You do not have r/w permissions on the /System

is there some other associated issue?

You can reinstall the macOS on top of your existing macOS and compare your results:

How to reinstall macOS Recovery (both M1/M2/M3/M4 and Intel) — How to reinstall macOS - Apple Support