Solution for changing Big Sur login wallpaper to custom.

applewarm wrote:

1. Just sharing a solution I've found on Stack Exchange. Credit to whoever discovered it.

System Preferences > Users & Groups.

2. Open lock to make changes.

3. Right click on user in left column > Advanced Options.

4. Copy UUID value.

5. Go to /Library/Caches/Desktop Pictures.

6. If it doesn't exist create Desktop Pictures folder.

7. Inside Desktop Pictures create folder with UUID value as name.

8. Right click on folder > Get Info.

9. Open lock to make changes.

10. Grant permission to Read & Write to user, admin, everyone.

11. Make sure FileVault and Guest user are deactivated.

12. Change desktop wallpaper.

13. Restart computer.

Big Sur will now always create a lockscreen.png file in the UUID folder matching the current wallpaper.

Tested on a 2018 MBP and works perfectly.

Enjoy!

Can we see a screen shot of your modified folder as you indicate:

 /Library/Caches/Desktop Pictures

Here is what I see by default:

for clarity are you saying create another sub folder with a tile of the UUID?

Do you place another picture in that folder, do you name with UUID number or do you name it "lock screen.png" ?

Do you delete the old "lock screen.png" ?

Right now that "lock screen.png" matches my login background, not the colorful Big Sur restart wall paper...?

I've been a long time Mac user as well, since the early 90s, MacOS 7.5 days so understand your point about being loyal.

Apple has changed, back then there was no iPhone or iPod, or app store which made then popular. It's amazing how they can push out updates to software and hardware like they do year after year and keep things running smoothly as possible.

They could address the login screen issue in a future software update though or you could submit feedback via product feedback.

I followed the instructions and it worked for me. I don't use File Fault so that's not an issue nor multiple users but would like the ability for it to work under the guest user if it's enabled.

You could check out OnyX when it's released for Big Sur and see if it allows you to change the login screen if you want to keep File Vault enabled and use your machine with multiple users.

I think what happened was the Desktop Pictures folder in Macintosh HD > Library > Caches > somehow over the beta period disappeared which caused the pictures to not sync to the login screen. This is just my theory.

If you don't want to follows the steps to change the login screen background that's on you. Just trying to help is all.

Please format your posts so they are easier to read rather then packing it into one block of text.

Welcome, rob185, to Apple Support Communities!

I do hope «Apple support» didn’t, actually, «recommend [you] put in a comment in a forum for it to be hopefully fixed on next update.»

That would be quite terrible advice.

What I hope they actually advised you to do is provide Product Feedback to Apple: Product Feedback - Apple.

Most particularly at Feedback - macOS - Apple.

brianofTX,

I'm glad it works for you when FileVault is disabled. I have it working on my own Mac.

Yes FileVault needs to be off for the login screen to sync with your desktop picture.

Apple engineers/ the mac product management team do not read these forms as they are community based so your best bet is to submit a feedback request and hopefully it will get a address in a future update for Big Sur.

I feel it could be an artists representation of Big Sur or the waves at Big Sur. If you don't like the colorful background, the best thing to do is to keep FileVault off and use the this solution until Apple releases a fix.

I hope this helps.

Hi Francois-Stanford,

Yes, it only works for single user accounts and one has to turn off FileVault as well.

Hopefully Apple will address this with a future update. What do you can do is submit feedback at this point and hope they read it. That's all you can do at this point.

Hope this helps.

StephCape wrote:

I agree with both petroc2 and Halliday - but it should be your choice - not forced upon you, don't you think?

Oh. I quite agree that the user (system administrator) should be able to choose what image is best for their system.

As Soren Pearson has written:

«Hopefully Apple will address this with a future update. What … you can do is submit feedback at this point and hope they read it. That's all you can do at this point.»

I would recommend using the macOS Feedback, and choosing the “Bug” report: this is preventing you, the system administrator, from setting the most appropriate Login Screen (User Selection Screen, or whatever Apple calls that screen, before selecting a User to login as) for your system.

Fortunately, I have had good experiences submitting “Bug” reports to Apple.

Halliday,

I did post an updated solution which clarifies a few steps and made them clearer back when appleworm was active. They had suggested that I do it as well since they weren't able to edit the original post.

Hope this helps.

It seems that the default startup wallpaper is in /System/Library/Desktop Pictures/Big Sur Graphic Day.heic with links to it. So theoretically one would have to change one of these links using the method described for Catalina. However this particular folder seems to be part of the sealed filesystem (the startup wallpaper is no doubt critical for the system). As I understand this protection, you have to renounce forever to the SSV protection since it seems not possible to sign the changes you made; indeed this is the point of this protection: not being able to make any change to system files. (see https://forums.macrumors.com/threads/words-of-caution-regarding-modification-of-system-files-using-csrutil-authenticated-root-disable.2276764/). So I guess the only safe way is to indicate our displeasure to Apple via https://www.apple.com/feedback/macos.html and hope somebody will listen.

Welcome, Moka.s-Onkel, to Apple Support Communities!

The provided “solution” only works for Single-User systems. (The steps are, actually, to make a Single-User system be recognized as such.)

In the case of recognized Single-User systems (with the Login Screen set to “List of Users”, rather than “Username and Password”), the Login Screen is actually skipped, and starts at the Lock Screen of the single user.

The user’s Lock Screen is always (when everything works correctly) based upon that user’s Background image.

We have yet to find out how to change the background image of the actual Login Screen.

The best course of action, especially for Multi-User systems, is to provide Feedback, to Apple, concerning the desire to change the background of the actual Login Screen: Product Feedback - Apple.

One could, likewise, request means for setting a user’s Lock Screen to have a background that differs from the user’s working Background.

Hi Bandara75,

First, I would uninstall CleanMyMac as it can do more damage then good. Why you shouldn't use it.

I assume you were able to change the lock screen before but after using CleanMyMac it reverted back right?

Second you could consider reinstalling MacOS via recovery mode which will keep your data but should allow you to change the login screen and revert the system back to where it was before you ran CleanMyMac.

In summary, Macs don't need cleaning applications as they can tend to slow it down rather then actually "clean it"

Hope this helps.

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.

ted2019 wrote:

i tried following it but I did not need to change that image in that dir as it was already changed. My iMac has 2 users so it does not work from what you’re saying if you have multiple users. I will try it on my Mac book which is a single user over the weekend.

Yes. At this time, what we are able to change is only the Lock Screen background, and allowing the Login Window to be skipped, in the case of a Single-User system.

On Multi-User systems, or systems where the Login Window is set to use “Name and password”, the Login Window is never skipped.

All would be good, however, if we had the ability to change the background of the Login Window!

Unfortunately, none of us have figured out the “secret sauce” to make that change, yet, nor has Apple provided us with any tools for making that change, yet.

The best any and all of us can do, at this time, along such lines, is to provide Apple our Feedback, directly: Product Feedback - Apple.

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.

Hello all,

Just wanted to chime in and say that I am experiencing this same... annoyance(?) and to join in this discussion.

Yesterday, before I discovered this popular thread, I created this one:

Big Sur Graphic Flash on Log Out

I have read through this current thread but have not seen any mention of the "Big Sur Graphic Flash" on log out and was wondering if anyone (or maybe everyone) is seeing that? As I mentioned in that thread, I'm guessing it's happening because the Mac logs out to the log in screen then quickly checks and sees that I have a single user account and goes back to my selected desktop background?

As suggested by many others in this thread, I'm going now to leave Apple some feedback about this nonsense!

Cheers!

Wengro wrote:

I don’t mind the [Big Sur] image or the forthcoming Monterey one as OPTIONS, but making them an unchangeable default (without annoying and insecure work-arounds) Login Screen/Lock Screen background is just NOT cool!

I agree that built-in, secure means for changing the Login Screen background should be provided by Apple. (The Lock Screen background usually seems to properly change with the individual user’s choice of Background.)

However, no amount of discussion, here, will be able to change anything along such lines.

The only recourse is to provide Apple direct Feedback, through their designated mechanisms, such as Product Feedback - Apple.