Solution for changing Big Sur login wallpaper to custom.

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Welcome, dpacheco_utd, to Apple Support Communities!

If your «startup screen» (user selection screen, login screen, or whatever Apple calls that screen) shows more than a single User choice (including any Guest users), then the “solution” presented in this Discussion will not help.

(Usually, the screen with the Apple logo, and the progress bar, seems to be called the “Startup screen”.)

If you can eliminate all users (including Guest users), other than your User Account, then you can follow the steps presented in this Discussion.

None of us have found a solution for multi-user systems, yet.

sallyrf wrote:

I followed all your very clear directions but it made no difference on my 2020 MacBook Pro. Do you have any other ideas? …

Do you have a Single User system: no other users, not even the Guest user?

If you have any other users, these directions won’t help much at all.

Did you disable FileVault? If FileVault is enabled, the result will be the same ol’ Login Screen (rather than the personal Lock Screen).

Is your Login set to show a list of your system’s Users, or to Username/Password? This was not included in the original set of instructions, because the List of Users is the usual default. Username/Password will always show the Login Screen (the «Big Sur Graphic.heic»).

The lock screen image (Big Sur Graphic.heic) is in the System/Library/Desktop Pictures folder and I can't make any changes to this folder no matter what I try.

Thanks. Sally

Yes. You are quite correct where the Login Screen (and default Lock Screen) is found.

However. That volume is a Read-Only volume, so, no, you cannot make any changes, there.

(If we could make changes, there, even those of us with multi-user systems would be able to change the Login Screen.)

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.

Mbbrown55,

I assume you have a Desktop Pictures folder located in Macintosh HD > Library > Caches.

For step 10 within the Desktop Pictures folder, there is a folder with your UUID value as the name. Right click that folder and come down to Get Info. Next click the lock at the button of the get info window and enter your admin password to your Mac to grant permission. Where it says Sharing and permissions select Read & Write for your user account, admin and Everyone.

You might have to click the + button to add the admin if it's not showing in the list.

For FileVault and Guest user, go to System Preferences. Click Security and Privacy and then click the tab for FileVault and make sure it's off.

Next for guest user, go to Users & Groups and make sure Guest user is off.

To change the desktop picture go to desktop and screensaver and change the desktp picture to the one of the big sur landscape which should cause the lockscreen.png file to be automatically created.

Reboot your Mac and your login screen should match your desktop picture.

Hope this helps.

Welcome, E. Kennedy, to Apple Support Communities!

I see you have not had success with applewarm‘s suggestions.

Unfortunately, there are a few nuances that were not included in applewarm‘s original suggestions:

1. Such only work for truly Single-User systems: hence the reason for having to disable the Guest account. Multi-User systems will always see the Login Screen (always the colorful Big Sur Graphic image), prior to choosing a User (provided the system is not using the Username/Password dialogue for logins).
2. Those suggestions don’t take into account that some people have chosen to use the Username/Password dialogue for logins: this approach, even for a Single-User system, will never show the user’s Lock Screen (with the possible exception of the user explicitly putting their computer into Locked mode). One will always see the colorful Login Screen with the Username/Password dialogue for logins.

None of us have found a way to replace the background of the Login Screen: it’s always the colorful Big Sur Graphic image.

Does any of the above help you see why your system is not doing what you want?

I did create the folder and the folder with the userID. I did everything as described, but still have that ugly login screen. disabled firevault. this is a single user laptop. so what did I fail to do?

pantload wrote:

Does this work for a mac that has multiple users? Does it get rid of the bright Multi-color big sir graphic doing this?

I have a multi user machine and this doesn't work...

Sorry, pantload, but this process does not work on «multi user machine[s]».

On Single-User machines, this process helps the system recognize that the system is Single-User.

This, then causes the Login Window to be skipped: the system skips to the Lock Screen of the recognized Single-User. (That is, provided the Login Window is set to “List of users”, rather than “Name and password”.)

On Multi-User systems the system cannot skip the Login Window (the one with «the bright Multi-color big sir graphic»).

None of us have found a workaround to change the background image of the Login Window.

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.

Welcome, ted2019, to Apple Support Communities!

Have you made sure that all the other conditions are met on your system?

The conditions are necessary to make sure that your system is recognized, by the macOS, as a Single-User system.

Multi-User systems are not helped by the provided settings.

However, there is one additional setting that was neglected: making sure the “Display login window as:” is set to “List of users”, and not “Name and password”.

What this all does is cause the Login Window to be skipped, skipping into the system’s Single-User’s Lock Screen (showing the lockscreen.png image for that user).

Thanks!

If I may, I want to point out to others (who, like me, may have failed at this so many times already after reading many online posts about this) that the place to find the Desktop Pictures folder (or to create that folder if there is none there) is inside your boot drive's Library/Caches folder... not inside the user/[username]/Library/Caches folder. In my case I had to create a Desktop Pictures folder and, inside that folder, create my UUID folder.

Applewarm's steps (where you change the desktop image as the last step before restarting) is the way to do it. But, I noticed that if you want to add a custom image to the UUID folder, so that the lockscreen image is your custom image, different from the desktop image, you need to define your desktop image first, via system preferences, restart the computer, then replace the lockscreen.png image in the UUID folder (which, if you look at it will be an identical image to the desktop you defined before restarting) with your custom image. Looks to me like whenever you change your desktop image via sys prefs and restart, the lockscreen image in the UUID folder gets replaced with the same image as your new desktop image (wiping out your custom image there).

I think.

Anyway... thanks applewarm.

It worked, thanks for posting these instructions.

As soon as I changed the desktop from Big Sur background to the rainbow and back I saw that the file had been created.

For Number 10, which folder do you grant permission to? For me I granted permission to both the UUID and desktop pictures folder.

A few suggestions to make your instructions clearer:

1. Go to System Preferences > Users & Groups
2. Click lock to make changes
3. Right click on user in left column > Advanced Options
4. Copy UUID value
5. Go to Macintosh HD/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 for user, admin and everyone for both the UUID folder and Desktop Pictures folders
11. Make sure FileVault and Guest user are deactivated
12. Change desktop wallpaper
13. Restart your computer

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