macOS 10.15 Read Only root

Rainer Müller raimue at
Sun Jun 30 11:21:12 UTC 2019

On 30/06/2019 04.15, Ryan Schmidt wrote:
> On Jun 29, 2019, at 19:53, Mark Anderson wrote:
>> Do we have any plans with how to deal with 10.15 not allowing us to create /opt if it doesn’t exist? Or does /opt just come with the file system? I can’t remember.
> macOS does not come with an /opt directory.
> I was not aware that macOS Catalina will prevent the creation of such directories, but I haven't read up on the new system yet. If that is true, then that sounds like a problem for us.

/opt will not reside on the read-only volume, but with the new concept of a
"firmlink" it will be placed on another volume.

I was told the full list of these writable paths using firmlinks can be found in


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