Big Sur login screen, custom wallpaper and several users

[rimvydukas]

Hi,
As you may know, there is no easy way to setup lock screen wallpaper in Big Sur. So here goes my problem and question.

1. Clean Big Sur installation with one user. I set up wallpaper for this user, restarted my mac and bam, this wallpaper was set as lock screen wallpaper even without me clicking on the user's picture. Great. Checked “/Library/Caches/Desktop Pictures” just in case and saw that UUID folder was created with lockscreen.png file in it.
2. Ok. Created another user, set wallpaper for this user, restarted my mac and saw this ugly standard wallpaper and two users pictures. Now behaviour is the following - when I click on first user picture, wallpaper is changed to my custom one. But when I click on second user picture - Big Sur shows standard wallpaper.
3. Ok so I logged in as secondary user and created UUID folder for this user in “/Library/Caches/Desktop Pictures” too. Logged out. Now the behaviour is the following - if I click on any user, wallpaper is changed to my custom one. Great.

Now here goes my major problem - when noone from these two users is selected (mac is at lock screen right after restart) - Big Sur shows standard wallpaper. So my question - does anyone know how to change this wallpaper to different one? Thanks.

 

[PeterHolbrook]

I've read A LOT of convoluted comments on how to change one's individual login screen. As far as I can see, most of that advice is perfectly useless and irrelevant, as there are easier methods to achieve the same result (for instance, the latest version of Onyx for Big Sur achieves it transparently). But none of this will solve the issue of the horrendous pre-login wallpaper when you have several users on your Mac. That particular wallpaper comes from either /System/Library/PrivateFrameworks/SystemDesktopAppearance.framework/Versions/A/Resources.DefaultBackground.jpg or /System/Library/Desktop Pictures/Big Sur Graphic.heic. Both files are in a sealed volume. In other words, replacing them with one particular wallpaper of your liking will require UNSEALING the volume, then at least one bless operation, creating a new snapshot, et cetera, and I suppose, once unsealed, the volume can't be left in a sealed condition. Because of this, I'm quite pessimistic that the pre-login wallpaper can be changed. If anyone knows better, let us know.

EDIT: I wonder if there might be a roundabout solution. Perhaps if we knew who the "owner" is of the pre-login screen (the one listing all possible users of the computer). I thought the process might be owned by root, but, if so, the superusers UUID doesn't seem to have the desired effect. Might the pre-login screen be owned by someone/something else, like a deamon, a "Setup User", an "Unknown user", an "Unprivileged User", the WindowServer or something like that? Each of these has its own UUID.

 

[RawIsDan]

Hi,
As you may know, there is no easy way to setup lock screen wallpaper in Big Sur. So here goes my problem and question.

1. Clean Big Sur installation with one user. I set up wallpaper for this user, restarted my mac and bam, this wallpaper was set as lock screen wallpaper even without me clicking on the user's picture. Great. Checked “/Library/Caches/Desktop Pictures” just in case and saw that UUID folder was created with lockscreen.png file in it.
2. Ok. Created another user, set wallpaper for this user, restarted my mac and saw this ugly standard wallpaper and two users pictures. Now behaviour is the following - when I click on first user picture, wallpaper is changed to my custom one. But when I click on second user picture - Big Sur shows standard wallpaper.
3. Ok so I logged in as secondary user and created UUID folder for this user in “/Library/Caches/Desktop Pictures” too. Logged out. Now the behaviour is the following - if I click on any user, wallpaper is changed to my custom one. Great.

Now here goes my major problem - when noone from these two users is selected (mac is at lock screen right after restart) - Big Sur shows standard wallpaper. So my question - does anyone know how to change this wallpaper to different one? Thanks.

Did you ever find a solution to this ? I've looked around with no luck and it's aggravating.

 

[ignatius345]

I don't actually mind the "waves" looking graphic that I see on my MacBook Air's login screen -- but the version that seems to have come preinstalled on my new iMac is nasty. I think it's a throwback to some old Aqua design from the early 2000s and I truly hate it. I hope the next MacOS release lets it be changed.

 

[rxtc]

That particular wallpaper comes from either /System/Library/PrivateFrameworks/SystemDesktopAppearance.framework/Versions/A/Resources.DefaultBackground.jpg or /System/Library/Desktop Pictures/Big Sur Graphic.heic.

Unfortunately not. Both places are definitely not the source of the login screen picture. I own an iMac M1 in Silver and my not changeable login screen picture is identical to "hello Grey.heic" from Desktop pictures in the old fashioned Aqua Style. DefaultBackground.jpg in SystemDesktopAppearance.framework is the rainbow style "Big Sur Graphic.heic" from Desktop Pictures, "Big Sur Graphic.heic" in Desktop Pictures is also the rainbow style and not the used "hello Grey.heic".
Same wave style as Ignatius345 in his post, but different color.

My suspicion is, that this login screen definition is anywhere in one the endless new APFS containers like iSCPreboot, xART etc., which are only visible if you run EtreCheckPro.