How to change login/lock screen on Lubuntu 20.04?

Hi all, I’m a Linux beginner and am still learning my way thru the command line.

I’ve recently installed Lubuntu 20.04 LTS and really enjoy playing around with it.

However I’d like to find out how to change the lock/login screen image on my installation, and have not been able to find the solution through my searching through the official documentation and this forum.

Also, I tried to install a script that supposedly would cause Bing’s daily backgrounds to be displayed on my desktop. Unfortunately at the end of the installation it ran into some problems, and restarting the machine failed to show the new desktop backgrounds as promised. So I ended up uninstalling the script. Here is where where I found the instructions for doing this:

If anyone has experience with the above and can tell me how to do it right, it would be great.

But that’s not really important. I’m more interested in finding out how to change my lock screen background, and would be thankful for any advice on this item.

Yeah I don’t think that Bing business has anything to do with your login/lock screen. For that, you want to look at the display manager, SDDM. There’s a config editor for it but it’s not quite ready for prime time. Even then, I’m not sure it would do what you want because SDDM only thinks about “themes.” The theme we use includes that particular wallpaper. You can find the theme in /usr/share/sddm/themes/lubuntu and the specific wallpaper there is named wall.png. Replace it with another wallpaper and there you go.

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Thank you very much for your quick response! I’ve found the file, will play with it and see what I can come up with.

Cheers, and thanks again.

No problem. Be well!

There is some documentation about it in the official Manual section of this website, explaining how to change the background, etc.

I’ve found it’s difficult to change the appearance of the log-in screen much because of the way SDDM is set up. My original idea was to make my own theme by changing the Main.qml file, but it’s not so easy because the PictureBox and PasswordBox objects are imported from other .qml files. I got around that by importing the markup language from those files into Main.qml and modifying it, but I feel this is a very messy solution.

By the way, you might want to take a look at @wxl comment in this post:

@Chris Thanks for the suggestion to work with SDDM. I went and took a look at it, but as @wxl noted, the config editor is still in development, and I don’t trust myself enough to go tweak SDDM directly on my own. I found out that the wall.png file in /usr/share/sddm/themes/lubuntu is actually a sym link that points to a .jpg image in /usr/share/lubuntu/wallpapers. I just went into that folder and replaced that image with another one, and that did the trick.

Thanks again for all your help, have a great day everyone!

Yeah that works, too. Glad you figured it out!

One more question, if I may: how do I get a screen capture of my login screen? I see that Lubuntu 20.04 came installed with ScreenGrab, but I can’t get that to work once I have logged out of my session. I’ve seen an example where a script needs to be run, but it requires that I switch my desktop to lightdm display manager, and I’m not sure if that will break something that I can’t fix.

Oh wow, that’s a crazy idea. I’ve never tried it before, but you could install scrot which is a command line screenshot utility (it’s what was in the old Lubuntu), and run it with something like --delay 10 and then lock the screen.

You can almost do it by running sddm-greeter --test-mode from the command line and then taking a screen shot of that.

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i3lock can do static images or a color:

Options are for mouse cursor, keyboard feedback, empty password response, failed attempts, and color code or image (PNG)

sudo apt install i3lock

https://i3wm.org/i3lock/
https://github.com/i3/i3lock

Edit the “Lock-Screen” entry in /usr/share/applications

[Desktop Entry]
Type=Application
Name=Lock Screen
GenericName=Lock Screen
Comment=Lock the current session
Exec=i3lock -c 000000 -p default -e -f -n
Icon=system-lock-screen
Categories=System;Screensaver;
OnlyShowIn=LXQt;