Updating System files

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:
  1. Boot the Mac in recovery mode and go to the terminal,

  2. Here I disable SIP using csrutil disable,

  3. Reboot back in to Recovery Mode, open the terminal again

  4. Remount the disk with write permissions using mount -uw /

  5. Make the edits

However step 4 no longer seems to work on Big Sur as I am getting an error:
Code Block
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?

Answered by Developer Tools Engineer in 613832022
The system volume is now read-only so you should seek to avoid modifying system files.
For those with a similar question, I found a similar post which is more active here.
Accepted Answer
The system volume is now read-only so you should seek to avoid modifying system files.

I would like to detail a reliable method for modifying the /System folder on macOS Sonoma/Sequoia. this is not intended behavior since you aren’t supposed to be able to modify it, however it works pretty well. The TL;DR is you need to do 5 things:

  1. Enable the root user using Directory Utility if not already done so.
  2. Disable system integrity protection from recovery mode terminal (csrutil disable && csrutil authenticated-root disable)
  3. Log-in as root
  4. Mount the system data partition to a folder && make changes to it
  5. Bless the volume as a startup snapshot and reboot.

(optional) 6. Re-enable SIP in recovery mode. I got the instructions from here: https://sites.google.com/view/delete-system-apps/home?authuser=1#h.203841rgwe44

Updating System files
 
 
Q