MacPorts and /opt/local on Catalina and Big Sur read only volumes

Ryan Schmidt ryandesign at
Sat Jun 26 03:20:27 UTC 2021

On Jun 25, 2021, at 21:03, Tabitha McNerney wrote:

> On a fresh Catalina or Big Sure system, if you cd to root / then sudo then try mkdir /opt or something else such as mkdir /hello the system won't allow it, I get this:
> mkdir: /hello: Read-only file system
> note: the MacBook I just tried this on also has FileVault enabled and its got one of those Apple T2 chips with a touch bar
> How does the MacPorts Catalina or Big Sur pkg installer work around this restriction?

I don't know that we're doing anything. It just works.

There is some mechanism, that I don't understand, by which the system volume and the data volume are combined into a single presentation. Presumably the Installer app knows that you cannot install to the system volume, so it installs MacPorts to the data volume.

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