How to change the login screen wallpaper in Catalina?

Ok everyone...

I've found the ultimate solution, it's super easy and it does work:

Credit goes to RobT43 at StackExchange!

Original post here!

PS: you can use your wallpaper of choice as is and just rename it, no need to resize it to 83,56 in x 83,56 in and all that!

1. Download and prepare your image for login screen. Remember to rename as Catalina.heic
2. Copy this Catalina to your usb, name the usb anything as you wish
3. Restart your mac and hold Command + R to boot into Recovery Mode
4. Enter your password and open Terminal
5. type the command:

cp /Volumes/Name of your Usb/Catalina.heic /Volumes/Name of your System Hard Drive/System/Library/Desktop\ Pictures/Catalina.heic

1. Restart your mac > go to System Preferences > Users & Groups > and you need to change your User name's picture, and some Login option to clear the cache.
2. Log out to see your new login screen.

Article with images can be found here: https://macplanet.vn/huong-dan-cach-thay-man-hinh-login-screen-tren-macos-catalina

Good luck!

Ok so I updated to Catalina 10.5.1 today and the login wallpaper reverted to the original Catalina one.

But I simply repeated the method I'd posted before and everything is back to custom now.

I'll post it again below since at this point it's kinda way back in the thread...

This works perfectly with no issues whatsoever or at least that I'm aware of.

My test is on a MBP 15" Touch Bar 2018.

Only issue/setback I've had thus far has been, as said, updating Catalina to the latest version.

''OnyX is a multifunction utility that you can use to verify the structure of the system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the Finder, Dock, Safari, and some of Apple's applications, to delete caches, to remove certain problematic folders and files, to rebuild various databases and indexes, and more.

Release Notes

WARNING:

There is a specific version of OnyX for each major version of the operating system.

Use the specific version, and don't try to use a non-compatible version.

OnyX 3.7.0 for macOS Catalina 10.15

Requirements: Mac Intel computer running macOS Catalina 10.15.

√ This version of OnyX will be available 10-15 days after the final version of macOS Catalina is released.''

i used OnyX to change  login screen wallpaper.

Yeah, it looks like the System folder is pretty much locked up. Haven't tried sudo and Terminal commands to rename and replace Catalina.heic, but simple drag and drop doesn't work and doesn't prompt for a password, so maybe root is required. Hope someone figures it out....

I've tried that through Terminal as admin user and root user, it still prevent any changes. I even tried it through recovery mode terminal, I made the change with ease and back up the original Catalina.heic by rename it. but when booting macOS Catalina, it restart before it reaches to the login window like it crashes everytime it sees a different Catalina.heic. I had to delete Catalina.heic and put the original heic back. While in Terminal, I checked the extended attributes and noticed there's a lot listed under the picture file that I wanted to put on login list. I removed all by typing xattr command with -c under that picture file name. The only thing that's listed is com.apple.macl that cannot be removed.

I typed ls -al@ Catalina*

to show the permission list along with others and the file I change to Catalina.heic shows "@" at the end of the permission read/white. This still did not solve it. This has something to do with the extended attribute because all the original pictures under /System/Library/Desktop Pictures has no extended attributes on any of them. I'm still learning about terminal and Catalina.

Ok so the Catalina version of OnyX does not have the login wallpaper options at all.

Looks like they couldn't figure out how to change it either ha!

I've always either used OnyX or like in Mojave it was easy to do manually.

What now?

Ah! I was able to resolve this! The extended attribute was not the cause. It's the size of the picture. I had to open Catalina.heic in photoshop and edit whichever I want then rename it as login.jpg. I went back to recovery mode and copied from my USB drive file (login.jpg) to /System/Library/Desktop Pictures and made sure its still named as Catalina.heic. Reboot and the login background works the way I expected.

I'm not an expert either. Just a simple basic command to do it after you get the correct size picture. Its suppose to be 83.56 x 83.56 inches (according to Photoshop). After you resize it to any of the application you like, save as jpg to the highest quality as you can get. Save it on Documents then reboot to Recovery Mode. Open Terminal:

You want to save the original Catalina.heic file in case if it doesn't work right for the first time by renaming it to something else.

type mv to rename it: /Volumes/(your hard drive name)/System/Library/Desktop\ Pictures/Catalina.heic

you will notice that when you type a few letters for the directory name, hit Tab which will complete a full directory name

example if your hard drive is Macintosh HD:

mv /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Catalina.heic Catalina.original.heic

Then move the picture file you want to System Desktop Pictures by copy and paste:

cp /Volumes/(your hard drive name)/Users/(username)/Documents/(file name)

/Volumes/(your hard drive name)/System/Library/Desktop\ Pictures/Catalina.heic

example, you can copy and paste the code by changing the username "joelm" to your username and Macintosh HD drive name to your drive name:

cp /Volumes/Macintosh\ HD/Users/joelm/Documents/login.jpg /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Catalina.heic

After that, just reboot the system and cross fingers that it works.

If you want to go back to original login picture. Go back to Recovery Mode and open Terminal:

rm is to remove/delete:

rm /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Catalina.heic

mv is to rename it:

mv /Volumes/Macintosh\ HD/System/Library/Desktop\ Pictures/Catalina.original.heic Catalina.heic

Reboot then you should have the original Catalina login window again. Please feel free to correct me if I am wrong here. Hopefully this helps.

1 of the 4 Macs (2015 27" iMac) that I've faced was the 'read-only' in Recovery Mode, I don't think this has something to do with SIP so I did the SIP dance on that one along with restarting to get it to work. If you type reboot on Recovery Mode, this did not work so I click on restart from Apple logo on top left. This works after I did the restart and SIP dance which is for some reason is odd.

My 2019 15" MacBook Pro with SIP enable has no issue doing so.

The test was successful on:

2019 15" MacBook Pro

2015 27" iMac

2014 Mac mini

2015 21.5" iMac

Great! Thanks Applewarm and RobT43, I'll give this one a try. I had to do this the hard way, trying to figure out why it didn't accept the picture I wanted to place in which is a 5k size picture so I had to open Catalina.heic in photoshop then edit it from there. Save As JPG and go from there.

During the test, confirmed that this works as well. It's very important to do this command after the first command shown in this post by RobT43:

sudo mount -wu /; killall Finder

If killall was not typed in, it will not let you do any modification in System folder.

This worked for me, yay! It obviously cleared the permissions issue I was getting before. What I did was what I was doing in Mojave, which is rename the Solar Gradient wallpaper to the default - in this case Catalina.heic - after duplicating both originals of Catalina.heic and Solar Gradient.heic. It's a nicely respectable login background, SFW and all, which is where it's seen, as the iMac I have at home is unable to update past High Sierra. Just as well, as I'm addicted to Thoth, which will never be 64 bit. Thanks!

The wallpaper went back to default when I restarted my computer. The wallpaper I chose only worked when I log out of the user. Is there a way to show the changed wallpaper after restart? I followed all the steps here.

The wallpaper went back to default when I restarted my computer. The wallpaper I chose only worked when I log out of the user. Is there a way to show the changed wallpaper after restart? I followed all the steps.