[Big Sur] sealed boot volume modification - help needed

[Rastafabi]

I am puzzled. I need to modify the sealed system snapshot of Big Sur. And I did from Recovery HD. However I cannot get the modification to be reflected within a new snapshot… What am I doing wrong?

1. I booted into recovery, opened terminal, unmounted and remounted the system volume to gain write access.
   

   umount /Volumes/Macintosh\ HD
   mkdir /Volumes/Macintosh \HD
   mount -o nobrowse -t apfs /dev/disk2s5 /Volumes/Macintosh\ HD

2. I added the desired file to the now writeable volume using cp
3. I checked wether the file actually got transferred using ls
4. last I snapshotted the volume and rebooted
   

   bless --folder /Volumes/Macintosh\ HD/System/Library/CoreServices --bootefi --create-snapshot --setboot

However upon reboot the file was nowhere to be found. So I restarted into Recovery HD and rechecked using ls, just to find the file indeed did reside in the system volume. As it was there I took a new snapshot, but still this did not work. What am I missing?

Any help is highly appreciated!

PS: I cannot disable authenticated-root because I use FileVault, thus I need to make the modifications from within the recovery volume.

 

[coso]

I will probably need to do the same to fix the EDID of my external screen by putting a file in “/System/Library/Displays/Contents/Resources/Overrides”. Is this the same problem? It's not enough to disable System Integrity Protection right?

 

[joevt]

For Catalina and Big Sur, user created Display Overrides should go into /Library/Displays/Contents/Resources/Overrides

Overrides there will override anything that's in /System/Library/Displays/Contents/Resources/Overrides

You don't need to do anything to write to /Library/...

 

[Rastafabi]

For Catalina and Big Sur, user created Display Overrides should go into /Library/Displays/Contents/Resources/Overrides

Overrides there will override anything that's in /System/Library/Displays/Contents/Resources/Overrides

You don't need to do anything to write to /Library/...

While this is true, it on works for "standard" .plist overrides, as it seems. I need to apple an .mtdd override, which apparently does not work this way…

 

[coso]

For Catalina and Big Sur, user created Display Overrides should go into /Library/Displays/Contents/Resources/Overrides

Overrides there will override anything that's in /System/Library/Displays/Contents/Resources/Overrides

You don't need to do anything to write to /Library/...

Really? This would be amazing. Guide for patch-edid.rb said to put it in system and it worked (I don't remember how I got it to work in Catalina). If it's even easier it's much better, thanks

 

[joevt]

While this is true, it on works for "standard" .plist overrides, as it seems. I need to apple an .mtdd override, which apparently does not work this way…

mtdd is for displays which use multiple DisplayPort inputs. What display is your mtdd for? I don't think anyone has successfully made an mtdd for 4K 144 Hz and 8K 60Hz displays.
Is it for a 5K iMac display?

Really? This would be amazing. Guide for patch-edid.rb said to put it in system and it worked (I don't remember how I got it to work in Catalina). If it's even easier it's much better, thanks

Yes, just make the override in the /Library/... folder. You might still need sudo. The /Libary/... path is where SwitchResX creates its overrides.

 

[Rastafabi]

mtdd is for displays which use multiple DisplayPort inputs. What display is your mtdd for? I don't think anyone has successfully made an mtdd for 4K 144 Hz and 8K 60Hz displays.
Is it for a 5K iMac display? […]

No, it is for a Philips 5k, which has the same panel as the Dell and HP 5Ks. I've been using a custom madd up until Catalina and needed to make a patched HP one thereafter for it to work. I think it still could work, if I only would get it to be included in the snapshots… It did work unmodified for beta5, but that was on an external disk without FileVault…

 

[FixMiller]

No, it is for a Philips 5k, which has the same panel as the Dell and HP 5Ks. I've been using a custom madd up until Catalina and needed to make a patched HP one thereafter for it to work. I think it still could work, if I only would get it to be included in the snapshots… It did work unmodified for beta5, but that was on an external disk without FileVault…

I'm in a similar situation, have you found a solution?

 

[Rastafabi]

I'm in a similar situation, have you found a solution?

Yes and no. The solution is ti disable Filevault and volume-sealing entirely, which is something I do not want to do. So for me I haven't actually found a solution.

 

[FixMiller]

Yes and no. The solution is ti disable Filevault and volume-sealing entirely, which is something I do not want to do. So for me I haven't actually found a solution.

Yeah, not an option for me either. Thank you for the update.