SDDM

Simple Desktop Display Manager (SDDM) is Article description::a modern [[display manager that supports both the X11 server and the Wayland protocol.]]

Emerge
Install :

If there are performance issues, it might help to add the sddm user to the video group:

Files
SDDM has two configuration files: the package installed and  which is used to override specific options. The second is not created by the package. KDE Plasma writes user changed options to. Both files have the same format. See comments in the file and for details on available options.

Prior to 0.18.0
Prior to 0.18.0 the configuration was only in. Some of the files may have had to be generated manually. If installing 0.18.0, skip ahead to Service section.

Keymap
To select the correct keymap on the login screen, add following lines to the file:

This file is not created automatically when the package is installed so you'll need to create it if you haven't done so already.

Next create the directory

and the file.

the first country code is the default. Finally set execute permissions on the file.

OpenRC
Set SDDM as the default display manager:

To start SDDM on boot, add xdm to the default runlevel:

To start SDDM now:

After logging in to the X session via sddm, it is a good idea to verify that ConsoleKit is working as intended. By typing all active sessions can be listed. The list should include your session, typically running on. This session should also read. Active being FALSE indicates an issue.

systemd
To start SDDM on boot:

To start SDDM now:

Plasma
Graphical configuration is integrated in Plasma 5 system settings by installing :

Long load time before SDDM shows the greeter
A low entropy pool can cause long SDDM load time - see upstream bug report. If using systemd, the graphical target is reached and then everything appears to hang. Moving the mouse or using the keyboard will make the SDDM greeter launch (faster).

Solve the problem by using, for example, the package to increase the entropy pool or by enabling RANDOM_TRUST_CPU kernel config option with a recent-enough CPU.

Permission denied errors in Xorg.log
The X server will not start and permission denied errors (such as the following) are present in the log file:

It is likely the sddm user has not been added to the video group. Running the following command should fix the problem:

Missing users
If the login screen is missing some user(s) to choose from, this might be caused by - standard   is 1000 and some existing users may have lower uids.

X11: Incorrect layout on high DPI with fractional scaling and multiple monitors
If a scaling setting such as 1.5 (150%) is used, the second monitor (and others) might display incorrectly. An example screenshot is included. Note how the second half of the screen is actually starting in the first half and the aspect ratio of this screenshot is incorrect.



To fix this, use a script which SDDM will run right after initializing X but before loading the login screen. The default script for this is. Copy this file to, for example, and make necessary changes.

Example script to fix using and  a scale of 1.5 with 2 4K monitors that are oriented horizontally and placed side-by-side:

Then, configure sddm to execute this script:

Remember that this script must be executable (e.g. ). DisplayCommand is a path, not a command with arguments.

If SDDM still shows the incorrect layout or reverts to prior behavior, check that the DE has not added its own settings to SDDM.

SDDM service starts but yields a black screen
On NVIDIA cards, SDDM appears to require DRM enabled and operational according to this closed bug report.

Ensure Direct Rendering Manager is enabled in your kernel. If it isn't, enable it, rebuild the kernel, and re-emerge nvidia-drivers.

Ensure the nvidia-drm module is configured to run at startup. For systemd, it's as simple as ensuring this empty file exists:

/etc/modules-load.d/nvidia-drm

Finally, ensure your GRUB_CMDLINE_LINUX_DEFAULT entry contains the necessary flag:

nvidia-drm.modeset=1