I understand that macOS has its own policies about how various standard Unix directories are used, and that these are (or at least have in the past been) documented in the "File System Programming Guide". I'm about to update to High Sierra (from Sierra) and wonder:

  1. have these policies changed in any way between 10.12 and 10.13; and
  2. does the update process force changes (e.g. by enforcing new policies or reimposing old ones that have been customized) in organization or existing permissions.

For example I see that it is no longer possible under 10.13 to chown /usr/local/, and wonder what other changes the update will make to these standard Unix directories in (a) structure, (b) permissions, or (c) my ability to change permissions or organize the directories.

1 Answer 1


No super big changes on directories is my feeling / opinion.

High Sierra changes very little with respect to SIP protection and you can easily use ls to read ACL and restricted status protecting from root / super user modification of files.

Everything that was changed materially was versions before. High Sierra does introduce APFS and the concept of snapshots and radically more efficient storage and access speeds - but on the UNIX directory level - this is a snoozer of an upgrade.

Your /usr/local change is the only one that's notable - you can't get rid of it* but you're free to roam within it and change things to suit your needs.

Apple provides additional details about SIP Protected directories.


* Of course, you can still get rid of SIP protected files / folders / directories by disabling SIP by doing the hokey-pokey of reboot, disable, reboot, change, reboot, re-enable, reboot (Assuming you want SIP in general but not for this one thing). But then, the next time an OS update comes, your work customizing the OS could (and eventually will) fail since the installer will then put the file back where Apple intended it to be - existing and protected by SIP.

  • Cool. So it sounds like the big changes, which I've weathered already withe earlier updates, are with SIP and other than the mentioned /user/local change (for which there's a easy fix), things should go smoothly (my concerns are largely about Homebrew, Homebrew Python, MacTeX, and Node). Correct?
    – orome
    Commented Nov 10, 2017 at 17:13
  • @Allan, FYI bmike does not like proper HTML links in his answers. Years ago he got all over me about setting proper HTML links in his answers! Commented Nov 10, 2017 at 17:21
  • @user3439894 My apologies - I do prefer having the raw URL visible since I am 95% on iOS and you can’t tell where a link leads. that being said - I can’t / don’t want to be the boss of anyone and when well meaning people like you and Allan want to fix things up I hope I’m super chill about it. Please both of you keep editing and making things better. I’ll ping you in chat if I want to guide things further - deal?
    – bmike
    Commented Nov 10, 2017 at 20:26
  • Ehm, minor technicality, but: "you cannot get rid of it". 1. Disabling SIP altogether? 2. Editing in that state the rootless.conf? Have both of these or has just one of these options changed as well? Commented Nov 10, 2017 at 20:42
  • @bmike you said, "...on iOS and you can’t tell where a link leads", When I want to see the raw URL of a hyperlink in iOS, I touch and hold on the hyperlink and it then shows the URL first with several choices after, Open, Open in New Page, Add to Reading List, Copy and Cancel. Now I'm on an older version of iOS, but I would think that Apple wouldn't remove such basic functionality in later versions, but oh well if they did. Commented Nov 10, 2017 at 20:47

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