The title says it all. After too many OS X and now macOS upgrades-in-place, my disk is cluttered with too much history. There is also the occasional small but unnerving issue that may just be resolvable by a clean install.

Moving from Catalina (10.15) to (10.16 version 11), my plan is to save just /Library and ~/.. Is any other path necessary to maintain personalized settings?

(After upgrading disk-to-disk—as opposed to time-machine-to-disk—I haven't been able to continue using my Time Capsule histories, and hence I'll be wiping these and starting fresh.)

  • Do you mean ~/Library and not /Library. What about your data e.g. spreadsheets and other work you do on the computer. What do you mean by ~/. ? Also why nit go to Big Sur now. I am doing this and the files I need to prunes are ~/.Library and ~/.* but ~/Library contains useful information e.g. licences and complex setups so these get done manualkly - its taken a couple of days
    – mmmmmm
    Jan 17, 2021 at 21:01
  • @mmmmmm Under macOS (and other unixes) ~/. is a shorthand for one's home directory (/Users/<id>). Hence ~/Library is part of ~/.. I'm not aware that ~/.Library has ever been used by macOS.
    – Calaf
    Jan 17, 2021 at 21:27
  • Sorry typo ~/Library. The Unix/POSIX standard for home directory is ~ adding anything to ~ is a different directory and definitly not recognised bu most users. It is defined in the shell e.g. gnu.org/software/bash/manual/bash.html#Tilde-Expansion and zsh.sourceforge.net/Doc/Release/… the latter says "A ‘~’ by itself is replaced by the value of $HOME. "
    – mmmmmm
    Jan 17, 2021 at 21:40
  • @Calaf "~/. is a shorthand for one's home directory" the /. is redundant there, since . is shorthand for the current directory (so ~/././././. == ~)
    – muru
    Jan 18, 2021 at 4:37
  • 3
    I'll dispute that "most". Who expects to see a redundant . there? I would think most people, like mmmmmm, would think that you meant to write ~/.* to mean "hidden files and directories" and forgot a *. Even ~/ would be significantly better than ~/.
    – muru
    Jan 18, 2021 at 6:40

2 Answers 2


Yes, a copy of /Library and ~/. (which includes ~/Library) will retain most of your personalised settings. You may want to also include /Users/Shared as it is used by a few apps (e.g. from Adobe) to store licences and/or settings.

But the copy will include much of your clutter and history. This will defeat the purpose of a 'clean' install.

A clean install requires you to erase the disk, reinstall macOS, reinstall applications and recover your documents, photos, etc. (but, sadly, not settings) from your backup. This process will require you to enter application licenses and re-establish settings.

You need to judge whether the time and effort of a true clean install is worth it for you.

Personally, I do a clean install every 18 months or so - but that is because I am something of an app junkie.

  • What about replacing master.cf with the content of master.cf.default and then starting again? Or delete /etc/postfix and reinstall macOS - that should restore the default configuration. I notice that in the current macOS those files are all dated 1/1/2020.
    – Gilby
    Jan 18, 2021 at 3:20
  • Both good ideas. The first didn't work. For the second, might it be enough to copy a clean /etc/postfix from another BSD?
    – Calaf
    Jan 18, 2021 at 4:55
  • 1
    Here is /etc/postfix/ from my Mac (unmodified). dropbox.com/s/rvblcvuhbrcnbs0/postfix.zip?dl=0
    – Gilby
    Jan 18, 2021 at 5:19

Some of /Library may not be copyable (or replaceable) due to SIP. And if you do copy back files, you might inadvertently overwrite files that needed to change in the update.

A better approach would be a TM backup → erase → install → use migration assistant to restore account and settings from backup.

  • Good point. Now the question is: what does one lose if one simply starts with a fresh (new) macOS with an empty /Library?
    – Calaf
    Jan 18, 2021 at 2:36
  • Unfortunately, some of the recent updates have changed some of my preferences back to the default. GRR.
    – WGroleau
    Jan 18, 2021 at 4:48

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