I have a macbook runnning Catalina. I would like to know if it's possible, when I am booting from an external SSD another version of Catalina to not be able to access the internal drive of the Macbook.

The first idea that comes to my mind would be to turn on Filevault on the internal drive and therefore it will ask for the decryption password on the external alternate operating system. While achieving its purpose, I doubt this is the only solution. Has anyone managed to 'disable' or remove read/write permissions when booting from an external macOS?

  • Maybe you can setup /etc/fstab on the external macOS to not mount the internal disk/volumes and set the read-only flag on it. -- UUID=$UUID none apfs ro,noauto, e.g. UUID=FAB060E9-79F7-33FF-BE85-E1D3ABD3EDEA none ro,noauto Read the manual page for fstab in Terminal. You can read the manual page for command in Terminal by typing command and then right-click on it and select: Open man Page You can get the UUID's using Disk Utility or from Terminal using diskutil. – user3439894 Feb 10 at 3:16

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