If they are already mounted, you can continue to the next section. There is one other thing you can try if you keep getting a message telling you that you do not have enough space to install Big Sur.So I wanted to reset my 2019 Macbook Pro, so I used CMD + R and went to disk utility and erased Macintosh HD I then went to reinstall MacOS Big Sur and I got about halfway through the reinstallation but then it stopped and went to a prohibitory symbol with a black background and just states to go to Apple Support.If you upgrade to macOS Catalina from an earlier version of macOS, the read-only volume is created during the upgrade process.
