How to change the login screen wallpaper in Catalina?

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.

The configuration of Catalina has changed and the system is on a separate volume that the user can't access even with SIP disabled.

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.

www youtube com/watch?v=cjpd5LSuIOc

Terminal Code Below

In recovery mode:

csrutil disable

To allow changing of filenames:

sudo mount -t apfs -wu /dev/disk1s5/Volumes

sudo mount -wu /; killall Finder

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.

Make sure you changed your profile avatar to something else to clear all the cache :).

More info with pictures can see in this article: https://macplanet.vn/huong-dan-cach-thay-man-hinh-login-screen-tren-macos-catalina

You can simple do it all in Recovery mode like this article:

https://macplanet.vn/huong-dan-cach-thay-man-hinh-login-screen-tren-macos-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!

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!

Check our this article to customize your login screen.

https://macplanet.vn/huong-dan-cach-thay-man-hinh-login-screen-tren-macos-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?

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.

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.