How to modify the read-only system volume of the bootable external drive?

Hi, I have a bootable external disk and the system volume is read-only.

I’m using macOS Monterey 12.6.1. And both macOS Big Sur and Ventura have the same read-only system volume.

I know how to modify the read-only system volume in the internal disk.

  1. Boot into recovery mode to disable System Integrity Protection and Signed system volume.
  2. Reboot back into macOS. And create a new folder and mount the system volume there.
  3. Modify the files.
  4. Create a new snapshot.
  5. Reboot.

Here are several links taking about this.

It seems that I can boot from the external drive and do the same thing to modify the system volume there.

But can I modify this read-only system volume of the external drive when I’m using macOS from the internal disk?

I tried the mount command above but it doesn’t work.

~ sudo mount -o nobrowse -t apfs /dev/disk2s2 ~/livemount
mount: ~/livemount failed with 75

I honestly have no idea, but the person who seems to have done the most investigation of the modern MacOS volume structure, external boot disks, and what is and isn’t possible, is Howard Oakley. If you haven’t already, I suggest browsing his site, and maybe posting a comment or sending an email asking your questions. He’s very responsive and has vast knowledge.

Other than if you’re running a Hackintosh, why would one ever want to do this?

My opinion after reading tons of articles by Howard is that he would discourage doing this. I’ve not seen him post any articles advocating the disabling of SIP and modifying the system volume or read-only system snapshot. Doing either seriously degrades the security features built into macOS.

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