I guess this is appropriate here since Big Sur is still in development Yesterday I created a new APFS partition with macOS Big Sur. I usually edit some files in /System/Library files to tweak my home setup to my liking, including some display settings. However the steps I usually take to be able to edit these files no longer work. These steps were: Boot the Mac in recovery mode and go to the terminal, Here I disable SIP using csrutil disable, Reboot back in to Recovery Mode, open the terminal again Remount the disk with write permissions using mount -uw / Make the edits However step 4 no longer seems to work on Big Sur as I am getting an error: mount_apfs: volume could not be mounted: Permission denied mount: / failed with 66 Is there another way to mount the file system with write permissions?