Solution for changing Big Sur login wallpaper to custom.

I do wish you had provided further information on what you are experiencing, Made-In-Italy.

When you Lock the Standard User account, do you or do you not get a screen that looks similar to that Standard User’s Desktop image?

How about when you Lock the Administrator account?

When you Log-out of any user account (even an administrator account) you should, generally, get the screen that presents a choice of users (one can, alternatively, set the login to always be Username and Password, with no indication of choices of users [security by obscurity]).

This screen will always have the Big Sur Graphic image («the rainbow colored background»).

We have not found a way to change this image, or the image used for this Login Screen («log in screen» or User Selection Screen).

However, for Single User systems (not even a Guest account), the «log in screen» (User Selection Screen, or Login Screen) will be “skipped”—going straight to that single user’s Lock Screen. (This is what the steps presented in this Discussion help facilitate.)

However, if you are Locking users/admin accounts, but not seeing a Lock Screen that looks similar to that user’s Desktop image, then there are other steps (related to this Discussion) that can help correct that issue.

pantload:

The screen that is called «the “Boot up” Big Sur screen» is the one that shows the Apple logo and the progress bar.

If your system is not recognized as a Single-User system, or if your login is set to use the Username/Password dialogue box, then the first screen you will see after «the “Boot up” Big Sur screen» will be the Login Screen, the one that either shows the Username/Password dialogue box, or the list of Users’ icons.

This is also the screen presenting the Big Sur Graphic (that brightly colored abstract image).

(Unfortunately, none of us have, yet, figured out how to replace the Big Sur Graphic on the Login Screen to anything else.)

In the case of the list of Users icons, once one of the User icons is clicked on, one is presented that User’s Lock Screen.

That screen should look very similar to that user’s Background.

In the case of a single-user system, that the system recognizes as such, the Login Screen is “skipped” to show that User’s Lock Screen, right after the Apple logo «”Boot up” Big Sur screen».

(The steps presented within this Discussion help make a Single-User system be recognized as such, by the macOS system.)

Yes. It was weird though it didn’t create right away. I kept the folder open and file vault off and it generates the ⛔️(Locked) folder by itself. It did take a few moments. If you have to turn file vault off then restart your Mac after it fully decrypts.

If you had to turn file vault off then restart your Mac after it decrypts just to be safe. (I did that). When you create the folder make sure the copy paste doesn’t make a “space“ in the naming. Set the permissions as they should be then restart. In the comments before, it took my folder moment to generate the folder. Once I get back to my laptop I can add photos and more information to replies.

charonspacexdragon wrote:

Turns out the OP solution is temporary. Does anyone know how to remove protections in order to change the actual file that macOS keeps pulling from. It’s in the System Library then Desktop Pictures folder.

The System Volume (what is mounted at the root of the directory system [at ‘/‘]) is both Read Only, and a filesystem “snapshot” (which is checked for integrity before the system will even be allowed to boot).

So. Without some highly specialized tools, along with specialized knowledge, making a change in that file will not be possible.

Besides. To obtain the desired result need not require changing that particular file.

Unfortunately, so far, the only thing we can change is the Lock Screen background for individual users.

For those systems that are recognized as being Single-User systems, this change is sufficient, since the Login Screen (provided the Login Screen is set up to be “List of Users”) will be skipped, to reveal that user’s Lock Screen.

Unfortunately, there are a number of things that can cause a system to not be recognized as a Single-User system. (That’s what the provided steps are for.)

For those of us that have Multi-User systems, the Login Screen will never be skipped, but we are still able to set the Lock Screen background. (This is easy to correct, if the system “forgets”, as occurred with one of my users with the last update: I simply reset that user’s Background and rebooted [not that I necessarily needed to reboot].)

Welcome, Ande_Landells, to Apple Support Communities!

You are entirely correct that the given solution only works for Single User Systems.

I’m sorry, but none of us have, yet, found a solution or workaround for Multi-User Systems.

The best course of action, at this time, is to provide direct Feedback to Apple: Product Feedback - Apple.

LeadMare wrote:

Thanks, Halliday.

Single-user system, Guest user Off.

Login screen shows just my login name and pwd entry field.

That is exactly your problem: you have the Login Screen set to “Username and Password”, rather than “List of Users”.

Change the Login Screen to “List of Users”, and let us know how things work for you.

…

LeadMare wrote:

Thanks again, Halliday.

I didn't see anything in System Preferences/Users & Groups that said "List of Users"

I turned on Guest User, but no relief from garish login screen.

…

Turn off Guest User.

Go to System Preferences -> Users & Groups -> Login Options, right under “Automatic Login” you’ll find “Display login window as:”. Set it to “List of users”, rather than “Name and password”.

Then let us know how things work for you.

I have verified that as conjectured in previous posts, it is exactly the file

/System/Library/Desktop Pictures/Big Sur Graphic.heic

that controls the just-after-boot user selection screen in a multi-user setup (hereafter the "Login Screen" as many other posters have termed it). I have managed to modify this file and set the Login Screen to show my company's logo, as desired. I describe the procedure below, but first:

MAJOR WARNINGS: Following this procedure will apparently leave your Mac in a state in which you cannot use FileVault, and must leave both Signed System Volume (SSV) and System Integrity Protection (SIP) off. This almost surely violates the terms of any Apple Care or warranty you might have, and may leave your Mac more vulnerable to security breaches. This procedure appears to be very much a one-way street. Also, to perform this procedure you need to be comfortable using the command line in Terminal to manipulate files.

So, I cannot recommend that anyone follow in these footsteps. You have been warned.

In any case, here's what I did on my 15" MacBook Pro running Big Sur 11.4. The process is based on the information in the post at https://developer.apple.com/forums/thread/649832.

1) Boot into Recovery Mode (⌘-R while starting up). Open the Terminal under Utilities. Enter the two following commands that disable SIP and SSV respectively, and then reboot (normally).

csrutil disable
csrutil authenticated-root disable

2) Copy the C language code file at https://raw.githubusercontent.com/fxgst/writeable_root/main/writeable_root.c to a convenient place on your computer; I will just call this file writeable_root.c

3) Make sure that the `clang` compiler is installed on your Mac. This probably means installing XCode. (I am not certain because I had already installed XCode, and clang was present on my Mac, and I think that's why but I am not 100% certain.)

4) Open a terminal window, and change directories to the one where you saved writeable_root.c, and compile it with the following command:

clang writeable_root.c -o writeable_root

5) Now run the program with

./writeable_root

6) This command will place that Terminal in a special directory which can access the System files in a writable way. So make sure you don't leave that special directory - only change into directories inside it. In our case, we just want to go to the spot mentioned at the top of the post:

cd System/Library/Desktop\ Pictures

Note there is no initial slash in the directory name in this command -- we are not going to the usual /System/Library, but to the special view of that directory accessible from inside the terminal session that writeable_root has created.

7) You may want to save the original login image (the one that has been described as "vivid" among other things); for example, with:

mv Big\ Sur\ Graphic.heic Big_Sur_Graphic_original.heic

8) Now replace that file with whatever image you want to appear on the (multi-user) login screen. For example, to sub in the lovely nighttime photo of grasses along the Big Sur coast, just do:

cp Big\ Sur\ Night\ Grasses.heic Big\ Sur\ Graphic.heic

9) When the file is as you want it to be, just type `exit` to leave this special shell session. NOTE your Mac will now automatically reboot -- and show you whatever image you substituted in under this filename at login!

10) However, as mentioned in the warning, at least in my case, the Mac will no longer boot at all if either SSV or SIP is turned back on, and I am unaware of any way of undoing the above changes. Certainly re-running writeable_root and putting the original graphic back did not return my Mac to an "Apple-approved" state, in that it still would not boot with SIP or SSV on.

Hopefully this information is of interest to anyone out there with a sufficiently strong itch to change that login graphic that they are willing to forego FileVault, SIP, SSV, and Apple Care. Cheers.

Hi,

I've found a suggestion on Reddit (not tested) for changing login background on a multiple user accounts system.

livello 1
Sakellaris
·
7m
This is my solution:
boot into the recovery mode
open terminal
type: csrutil disable
press enter
type: mount -uw / /dev/diskXsY <--

Attention!!! X=your Big Sur disk from 'diskutil list'
Y=your Big Sur disk slice
Now the Big Sur volume should be writable
6. Reboot normaly
7. name your own grafic image as Big Sur Graphic.heic
8. copy your own grafic image in to Macintosh HD
9. reboot into the recovery mode
10. open terminal
11. type: mount -uw / /dev/diskXsY <--

Attention!!!! X=your Big Sur disk from 'diskutil list'
Y=your Big Sur disk slice
12. type: cd /
13. type: cd /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures
14. type: mv /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Big\ Sur\ Graphic.heic /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Big\ Sur\ Graphic.heic.orig
15. type: mv /Volumes/Macintosh\ HD/Big\ Sur\ Graphic.heic /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Big\ Sur\ Graphic.heic
16. Reboot
Now you have your new login background
17. Reboot into the recovery mode
18. open terminal
19. type: csrutil enable
20. press enter
21. reboot e voilá
¯\_(ツ)_/¯

I think I should note that after an systemupdate you get stuck with the terrible APPLE login screen again and have to repeat placing your own png picture in the /Library/Caches/Desktop Pictures/UUID value folder . And indeed you do not have to name it lockscreen of course.

By the way: I think you also do not have to change the permissions if you do it this way since only you are puting something in the folder.

Also command+I the folder and give permissions at the bottom of the box to admin and everyone read/write

Step 11 is very important: Turn off FireVault and disable Guest user; otherwise the procedure does not work.

Soren Pearson:

What StephCape wrote was «I changed the 'Login Options' to 'Display login window as: List of users' (instead of 'Name and password' as I had it)».

This seems to be its own step.