macOS 10.15 Read Only root

Mark Anderson mark at
Sun Jun 30 21:19:19 UTC 2019

I actually just tried. I have an /opt but I can create and delete other
things in the root. So we may be ok. I’ll keep an eye on it.

Obviously anything in /bin or /usr that isn’t /usr/local is off limits.


On Sun, Jun 30, 2019 at 10:50 AM Kridsada Thanabulpong <sirn at>

> Hi,
> I have been running Catalina for a while and from my quick testing of
> creating .rootro, reboot, and mkdir /sw, the whole process went through
> just fine and /sw become writable (thanks to firmlinks).
> I couldn't try creating /opt because I already had it from Mojave.
> So far, the only issue seems to be you cannot completely remove /opt or
> /sw anymore once they're created. mkdir is fine, but rmdir'ing them will
> result in "Operation not permitted" error.
> I'm not able to test if this is still the case with the Public Beta
> (my MacBook has battery defect). I can experiment again once I regain
> access to a Mac.
> Regards,
> Kridsada
> Ryan Schmidt <ryandesign at> writes:
> > 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.
> >
> >
> > Just a reminder, make sure that anything discussed about Catalina on
> this mailing list is information that has already been publicly released.
> >
> >
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