Setting up 2 MacOS partitions to use and back up the same shared Document partition

Question

my question is similar to another question, but I need a different aspect of it that is not asked and answered there.

So I would like to access and backup my Documents folder from different MacOS Versions. There is the way to move the complete Home folder over to the dedicated partition, but this most likely breaks the System and the Photos database, if different OS versions access their settings files.

So I just want to access these Folders from both Partitions:

• Documents
• Fonts (might be tricky)
• Movies
• Desktop

I suspect that those don't contain System-breaking configurations and they are the most critical.

How can I safely tell the system that these, and only these are in another place, and still have them backed up with a time machine backup?

Here's the partitioning of the Machine (same as in the cited question):

• A partition A with MacOS version X.
• A second partition B with MacOS version Y.
• A third partition C with shared data. I would like to use partition C from A and B as default locations for the abovementioned folders.

Answer 1

I preferred using iCloud or OneDrive.

I don't want to be resonsible for backing up my documents, especially when we live in dwellings that can be total losses to fires, natural disasters, etc.

I am now leaning towards Microsoft 365.

In your case though, I don't think you need a third partition. macOS doesn't respect file permissions that it deems is from a different install.

My advise is because you solve your identity and ownership issues, in a simple way.

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I am not sure if you need a Directory Service to make this work, but if you want to go that route, you couple create fileshares that connect automatically through AFS or SMB, and hopefully avoid identity gotchas.

I have FOSS way to do this but its at least 20 steps. If you like I can produce it.