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  1. You can find below the easiest way to change your lock-screen picture on MacOs Catalina:

    1. System Preferences > Security&Privacy > make sure FileVault is off.
    2. System Preferences > User&Groups > Right Click on User after you unlocked settings > Advanced Options > Copy UUID
    3. Go > Library/Caches > Make New Folder and rename to Desktop Pictures > Right click on the folder > Get info > Below where Sharing&Permissions is > make the admin read&write.
    4. Open the new folder named Desktop Pictures > Make another folder and name paste the UUID as the folder’s name > Get info on the new folder > make admin read&write as well.
    5. Reboot mac.
    6. Acces Library/Caches/ Desktop Pictures/ UUID folder > change picture with anything you want.
    7. Reboot computer.

    1. Did not work for me. I put the picture I wanted (a JPEG) into the UUID-named folder, rebooted, and got the same supervillain-volcano image on my login screen. Added the Administrator with read&write to the permissions on the JPEG, rebooted again, same result. Converted the JPEG to HEIC, added Administrator with read&write, rebooted. Login picture still unchanged.

      Does the file in the UUID-named folder need to have a special name? I feel like the instructions got really vague at step 6…

  2. This worked a treat under Catalina, but not Big Sur. All okay up to Step 5:

    sudo mount -wu /; killall Finder

    where I get the response

    mount_apfs: volume could not be mounted: Permission denied
    mount: / failed with 66

    Really appreciate it if anyone can help. I hate the Log in BG…

    Cheers from London, Brett

  3. I’ve found a solution which I have written in here.

    which I have written in here:

    i think in most cases it is the missing of a folder in “/Library/Caches/Desktop Pictures”

    this must be created with the name of the user’s UUID. In addition, the rights for the system to write must be set.

    after that macOS should put a “lockscreen.png” file for the login there again.

    Should work for Catalina and Mojave.

    1. oliver (and norbi) – yours are the best solution. works perfectly and i have been doing this every iteration of macOS after updating.

      keep in mind for those reading, “lockscreen.png” must be in the caches folder. one could rename their favourite png image to lockscreen.png and place it there. furthermore, one could have a different desktop image and lock screen image simply by locking the lockscreen.png via the Get Info window before changing the Desktop Picture.

  4. Great it works thanks, but please how to reverse this ?? I’m still getting System mounted on each start. any solutions ?

  5. Having chosen to display, at random, one of my own photos from a folder as a desktop picture, OSX has arrogantly chosen to use the first in alphabetical order as the logon photo. So the procedure listed above is simply not relevant. I need to experiment further. Pretty poor of Apple not to do make this is simple process.

  6. How To Change The Lock Screen
    1) Select or create an image and name it: Catalina.heic
    2) Go to: Finder > Applications > Utilities > Disk Utility
    a) Select Macintosh HD
    b) Click on Info
    c) Read BSD device node (mine says disk1s1)
    3) Shutdown computer
    4) Restart computer – holding down the [command] + [R] keys until it boots
    5) Select admin account and enter in the password
    6) Click on utilities and open Terminal
    7) Enter: csrutil disable and press return – you have now disabled the integrity
    8) Restart computer
    9) Go to: Finder > Applications > Utilities > Terminal
    10) Enter: sudo mount -t apfs -wu /dev/[system ID]/Volumes
    11) Enter: sudo mount -wu /; killall Finder
    12) Go to: Finder > Go > Go to Folder
    13) Enter: /System/Library/Desktop Pictures
    14) Select image: Catalina.heic and rename it: old.Catalina.heic
    15) Drag-and-drop the image you named: Catalina.heic into the open folder
    16) Go to: Finder > Applications > Utilities > Terminal
    17) Enter: diskutil apfs updatePreboot /[system ID] and wait for it to finish
    18) Close all open windows
    19) Shutdown computer
    20) Restart computer – holding down the [command] + [R] keys until it boots
    21) Select admin account and enter in the password
    22) Click on utilities and open Terminal
    23) Enter: csrutil enable and press return – you have now enabled the integrity
    24) Restart computer

    1. the lock screen is a same as your Desktop Picture in System Prefences>Desktop & Screen Saver>Desktop

      1. That’s the image used for the lock screen once a user has logged in, it’s not the startup screen which initial screen seen when starting before any user has been chosen. For MacOS 11.2 aka Big Sur (what’s with the nonsensical OS names?) the image is: /System/Library/Desktop Pictures/Big Sur Graphic.heic

        The above process will likely work fine to replace this image with whatever you want. There are also images for Day and Night, but they are just aliases pointing to the Graphic image.

  7. Worked like a charm. But is ist correct that the desktop picture has changed to the same one I just for the login screen? I had wished for two separate ones.

    And one more question, doing all that my login password doesn’t show any signs any more. I can type them but they remain “blind” like as you are typing the password in terminal

  8. This worked great, but within a few days, my system became unstable and my computer began to crash weekly. I can’t be sure this was the problem, of course, but after a couple of months I had to reinstall the OS. Just sayin’.

    1. I have been loving the HEIC images. And, I notice a direct correlation to my system being *weird*, and then crashing (startup disc becomes corrupted, yikes flashing folder with a qusetion mark), and I have to reinstall OS. I haven’t done this bit, but just using custom HEIC images for whismy and fun.

  9. Unfortunately, it doesn’t work on my mid 2012 Macbook Pro. As soon as I turn on the FileVault encryption, the login background goes into plan grey and no way to turn it back to Catalina’s wallpaper. While the SSD is not encrypted, the background is fine. I tried your steps to check if the files are there and not corrupted or something.. but everything looks fine. So I have no idea why it is happening.

  10. Dear John- Switch to Boot camp and Windows 10? Are you kidding? Get off this Mac conversation and go back to your clunky operating system of choice.

  11. I appreciate the detailed instructions; however, this did not work for me. Any suggestions would be most appreciated. My guess is the name of the disc is the problem? The hard drive is disc0, there is a ‘container disc1’ that has ‘Macintosh HD’ identified as ‘disc1s2’. first I tried sudo “mount -t apfs -wu /dev/disk1s2/Volumes” and then “sudo mount -t apfs -wu /dev/disk0/Volumes”.

    Suggestions are most appreciated 🙂

  12. This was important enough for me to try, and it worked, but there are a couple of rough spots in these instructions, one of which I hope my pointing out is helpful to someone else who might be a bit timid about jumping in.

    What is “the identifier for your system”? I found the correct identifier for my system after looking very closely at the screenshot included in that step (#4). The Macintosh HD listed on the left has two entries: the second has ” – data” appended to it. Use the one without ” – data”. The “identifier” is listed as “device” in the list in the screenshot (last item), and, if you follow the instructions’ advice to click on the “info” button (indicated by the arrow), the “BSD device node” on the info list. Hope that is helpful.

  13. It worked but only for my initial log in screen. If I restart I get the changed image, but if I log out it returns to the original Catalina display until I shut down or restart again. Is that how it’s supposed to be? I thought the image would change regardless of how you log off.

  14. This is ridiculously complex for something that should be a simple job. The wisest thing to do is to install Windows 10 using Bootcamp and kick yourself for buying a Mac in the first place, like I do every day.

    1. True, what a hassle for something this simple, reading the comments about the problems people run into while doing this makes me keep the old background, quite annoying

  15. This worked great for me except for one thing. After changing the image, the icons for “Restart” and “Shutdown” on the login screen are all white. Similarly, the characters inside the password box are white as well. Has anyone else encountered this — and do you have ideas for how to fix it? Thanks.

  16. Thanks so much for this. What a palava! In step 9 I had an issue which is not documented here: After renaming the Catalina-heic file to Catalina-original.heic I moved the new Catalina.heic file into the directory but got an error message to say that there was a newer version of this file in the directory and did I want to replace it. I chose to keep both which resulted in the new file being renamed CatalinaCopy.heic. I then renamed that file Catalina.heic and all is well.

  17. followed exactly, checked and double checked, and now i can’t boot…even ran 1st aid in recovery…when clicking info, DON’T choose the first disk listed as BSM…i should have used disk2s5 instead of disk1s5…[bricked]

    1. You need to enter “sudo mount -t apfs -wu /dev/YOURSYSTEMDISKNAMEHERE/Volumes”

      In my case it was “sudo mount -t apfs -wu /dev/MacProSSD /Volumes”

  18. Thank you for the detailed post. Unfortunately I am just too chicken to try this. WAY over my head, and I have used Macs since the original Mac with 128K of memory came out. Each time Apple changes the OS it just gets let reliable, more complex and less intuitive. The original programmers were Very focused on intuitive user interfaces. How about just a “set startup screen”. Apple has forgotten their roots.

  19. I was unable to rename the .heic file or paste the replacement one into /Desktop Pictures folder…?

    Any ideas?

    1. you may have missed a step or you may have encountered the same issue I did – see my post to see what I did to get this to work.

  20. So when I load the terminal screen, before the command can be entered, it is prefixed on my Catalina iMac with “bash-3.2#” and entering the command “crsutil disable” after that throws up an error that it cannot find crsutil.

  21. Wow! This is complicated, however, I have talked to Apple care numerous times and the “expert” tells me they don’t know how. Even went in person to get my computer fixed and asked to change this, several of them tried and were unsuccessful. Soooooo at least you have given some directions. Unsure if I am able but will try.

  22. I agree with the others, the directions for doing this on macOS Mojave was far simpler

    1. Find an image or photo to use as a background photo. It is important that this picture should fit the resolution of your screen. Thus you may want to know your screen resolution. You can find that easily. On your Mac, go to Apple Menu > About This Mac and click the Displays tap. you may find it to be 1280×800.

    2. Save this image on the desktop as a .jpg file. You can also find images online.

    3. And then rename your image as Mojave.heic (HEIC: High Efficiency Image Format).

    4. Now, Open Finder and go to
    Go > Go to Folder… (or press Command-Shift-G)

    5. Enter /Library/Desktop Pictures/ and then click Go.

    6. Find the Mojave.heic file.

    7. As a backup method, change its name to something like Original-Mojave.heic (so you can change back later). You may have to enter your admin password.

    8. Drag the new Mojave.heic image into the folder and exit (copy and paste). Again you will have to enter your admin password.

    9. Restart your computer

    10. Done. You’ll see your new background.

    1. Yeah, welcome to Catalina. Apple is bending over backwards to prevent customizations and branding. Such a waste of time for something we should have every right to change on our own. MS is doing similar things in OS10 as well.

  23. Sorry I’m new to Mac. Can you please tell me how do I find out what is the “identifier” of my system, alike disk1s5?

    1. +1 to this question. I’m not new to Mac, but when I do a “df” in my terminal window I see:

      /dev/disk1s1 mounted on “/”
      /dev/disk1s2 mounted on “/System/Volumes/Data”
      /dev/disk1s5 mounted on “/System/Volumes/Data/home”

    1. Unfortunately, due to numerous changes to core system functionality in MacOS Catalina, this is the only way to change the login screen background.

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