Change login screen in Sierra

Really! Well I wonder whats happened to mine then, the only thing that happens is that it adds the alt symbol to 'Enclosing Folder'.

I have a 2010 Macbook Air where it works and a late 2012 iMac where it doesn't. Both machines run Sierra 10.12.

Wish I could find out why they react differently.

I've just found that it works on the iMac if I press the Shift key instead of the Option key.

I started a new thread for this issue here.

I have done this before, but Sierra is not letting me change the login screen. I've tried restarting, and no luck. It still shows the foggy pic of mountain found in the System>Library>CoreServices>DefaultDesktop file. Can you spot what I'm doing wrong?

Please do not touch anything in the System folder, leave it well alone. And the defaultdesktop file is an alias and nothing to do with the login screen.

Next the image you included is the correct location for the login image, you can create a png file in Preview

name it com.apple.desktop.admin.png, then save it in the location Macintosh HD/Library/Caches.

I'm confused, sorry. Why do you say that file has nothing to do with login screen?

That is the image that appears on my login screen and won't go away, even though I have followed the instructions to make a file named "com.apple.desktop.admin.png", as shown in previous picture I posted.

That file as its name suggests is the default desktop file, not the image you get at login. The login image is the file

in the path Macintosh HD/Library/Caches.

Do you have your mac set for Auto Login, bypassing the need to enter a password to enter your mac. The reason I mention this is because I think you may have it set to Auto Login, and therefore it is opening up on Desktop 1 (if you have more than one set) which is by default the Sierra desktop image unless you have changed it in System Preferences>Desktop. An unchanged login picture will be a blurred version of the default image, with your user image

a space to type your password, and the restart, shutdown and sleep buttons.

If the mac is set so you need to enter a password before accessing the mac then the Sierra default picture is shown as blurred, however as mentioned above in previous posts you can replace that image in Macintosh HD/Library/Caches

with your own image, named as before, com.apple.desktop.admin.png. This should take effect after logging out and then in again, or after a restart. This will only work if you have your mac set so you need to enter a password to access your account.

Is your account an Admin account, if you are the sole user of the mac then your account should be Admin by default.

This is what a default login screen should look like.

This is my login screen. It is not set for auto login, as there are two users. (Also, before update there was a login icon for a guest user, which I still have enabled in System Preferences, but no apparent way for one to login...?)

This is my Library/Caches folder:

When I replaced login screen on El Capitan, there was already a file with name "com.apple.desktop.admin.png" that I had to replace. In Sierra, there was no such file. I inserted the file as shown, but the login screen remains the same.

So, I remain confused....

Do you have File Vault enabled? That would disallow the guest user, I believe.

for me it simply worked to rename the desired background to sierra.jpg in library/desktop pictures/. However, this will still show a blurred login screen. Is there a way for an unblurred wallpaper on login screen like it was possible under El Captain?

If there is no file in the Caches folder then Sierra will default to a blurred image of the Default desktop image for the login picture.

You can of course input your own image as you have done, but needs to fall into certain criteria.

It helps if you have an image editor like Photoshop or similar. The file needs to be in RGB colour mode, sRGB or Adobe RGB. Make sure the file is also 8bit. It is also important that the image must be a 'layer' rather than the default Background layer, if that makes sense, screenshot below.

New login screen.

when I go to my /Library/CoreData folder, there is nothing in it but an ExternalRecords folder and no other files. Inside it there is an HTMLNotes folder (which is empty) and another that is a long string of numbers and letter with dashes. I read another string on reddit that says it's in /System/Library/CoreServices/DefaultDesktop.jpg -- but that's an unblurred alias of the login image -- and my iMac won't let me change that pic.