SDDM

Simple Desktop Display Manager (SDDM) is a modern display manager that supports both the X server and the Wayland protocol.

Installation

USE flags

Emerge

Install x11-misc/sddm :

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

Configuration

Files

SDDM has two configuration locations: the "system configuration" directory, /usr/share/sddm/sddm.conf.d/, and the "local configuration" directory, /etc/sddm.conf.d/, which is used to override specific options, as described by sddm.conf(5) . Changes should not be made to the files in the system configuration directory.

KDE Plasma writes changed options to /etc/sddm.conf.d/.

Refer to the sddm.conf(5) man page for details on the file format and the available options.

override.conf and Xsetup files

Some configuration cases require some commands to be executed before starting the X server and showing the greeter screen. For these cases, use a custom Xsetup file.

Create an SDDM local configuration directory if it does not exist:

Then create and edit the file /etc/sddm.conf.d/override.conf, with the following lines in it:

[X11]
DisplayCommand=/etc/sddm/scripts/Xsetup

Next create the directory /etc/sddm/scripts and the file /etc/sddm/scripts/Xsetup:

#!/bin/sh
# Xsetup - run as root before the login dialog appears

# Add various commands here for execution on SDDM start.

override.conf and X11 rootless mode

By default SDDM runs in X11 as the root user. This may be considered a security risk.

Since x11-misc/sddm version 0.20 it is possible to run SDDM in X11 rootless mode instead.

The display server configuration must be overridden using /etc/sddm.conf.d/override.conf, as described in the override.conf and Xsetup files section above. To do so, add:

[General]
DisplayServer=x11-user

override.conf and Wayland mode

Since x11-misc/sddm version 0.20 it is possible to run SDDM in Wayland mode.

Weston

SDDM supports several Wayland compositors. This first example uses SDDMs default compositor, Weston, for systems where kde-plasma/plasma-desktop is not used. First install dev-libs/weston with the kiosk USE flag enabled.

The display server configuration must be overridden using /etc/sddm.conf.d/override.conf, as described in the override.conf and Xsetup files section above. To do so, add:

[General]
DisplayServer=wayland

Additionally, it is possible to add a [Wayland] section to that file, e.g.:

# ...
[Wayland]
CompositorCommand=weston --shell=kiosk

Kwin

Users of systems using kde-plasma/plasma-desktop may want to use Kwin as the compositor instead. To do so, override by defaults via /etc/sddm.conf.d/override.conf, as described in the "override.conf and Xsetup files" section above:

[General]
DisplayServer=wayland
GreeterEnvironment=QT_WAYLAND_SHELL_INTEGRATION=layer-shell

[Wayland]
CompositorCommand=kwin_wayland --drm --no-lockscreen --no-global-shortcuts --locale1

elogind (OpenRC) workarounds

Running SDDM in Wayland mode on an OpenRC/elogind system requires additional configuration. The main challenge is that elogind does not always set XDG_RUNTIME_DIR for sessions started by SDDM's Wayland helper chain.

seatd

SDDM's Wayland compositor (typically Weston) needs a seat manager. While elogind provides seat management for X11 sessions, Weston uses libseat which works best with the seatd daemon.

Enable the server USE flag:

sys-auth/seatd server

Rebuild and start the service:

Add the display manager user and the login user to the seat group:

Weston kiosk shell

The kiosk USE flag must be enabled for Weston:

dev-libs/weston kiosk

Fixing XDG_RUNTIME_DIR for the greeter

SDDM starts the Wayland greeter via sddm-helper-start-wayland, which launches Weston and then the Qt6 greeter inside it. On elogind systems, XDG_RUNTIME_DIR is not set for the sddm user in this context, causing Weston to fail silently.

Back up the original binary and create a wrapper:

#!/bin/sh
if[-z"$XDG_RUNTIME_DIR"];then
exportXDG_RUNTIME_DIR="/run/user/$(id-u)"
mkdir-p"$XDG_RUNTIME_DIR"
chmod700"$XDG_RUNTIME_DIR"
fi
exportSEATD_SOCK=/run/seatd.sock
exec/usr/libexec/sddm-helper-start-wayland.real"$@"

Fixing XDG_RUNTIME_DIR for the user session

The same issue affects the user session. SDDM's wayland-session script starts a login shell which sources /etc/profile. Create a fallback:

if[-z"$XDG_RUNTIME_DIR"];then
exportXDG_RUNTIME_DIR="/run/user/$(id-u)"
if[!-d"$XDG_RUNTIME_DIR"];then
mkdir-p"$XDG_RUNTIME_DIR"
chmod700"$XDG_RUNTIME_DIR"
fi
fi

Export the seatd socket path globally:

exportSEATD_SOCK=/run/seatd.sock

Troubleshooting

Technical background

On systemd, logind automatically creates /run/user/<uid> and sets XDG_RUNTIME_DIR for every PAM session. On OpenRC with elogind, this works for most login paths but fails for SDDM's Wayland helper chain because sddm-helper launches sddm-helper-start-wayland (for the greeter) or wayland-session (for the user session) in a way that elogind's PAM module does not propagate the variable into the child process environment.

Summary of required changes

Keymap

To select the correct keymap on the login screen, add the command setxkbmap to the /etc/sddm/scripts/Xsetup file, as described in the "override.conf and Xsetup files" section above:

#!/bin/sh
# Xsetup - run as root before the login dialog appears

# ...

# First keymap will be gb
setxkbmapgb,us

The first country code is the default.

Multimonitor configuration

The greeter location can be set by xrandr configuration in /etc/sddm/scripts/Xsetup, as described in the "override.conf and Xsetup files" section above. Firstly, install xrandr:

Then use xrandr to list connected monitors:

DP-2 connected 2160x3840+0+0 left (normal left inverted right x axis y axis) 597mm x 336mm
DP-4 connected primary 3840x2160+2160+0 (normal left inverted right x axis y axis) 697mm x 392mm

The above example lists two connected monitors: primary (DP-4) and secondary (DP-2), meaning the following lines should be added to the /etc/sddm/scripts/Xsetup file:

#!/bin/sh
# Xsetup - run as root before the login dialog appears

# ...

# First, set DP-4 as primary
xrandr--outputDP-4--auto--primary
# Second, DP-2 will be placed on left of DP-4 and rotated by 270 degree clockwise.
xrandr--outputDP-2--left-ofDP-4--rotateleft--noprimary

After reboot SDDM will show the greeter in DP-4 monitor.

Service

OpenRC

If gui-libs/display-manager-init is not present, emerge it with:

The configuration file should be modified to use SDDM:

CHECKVT=7
DISPLAYMANAGER="sddm"

In its default configuration, SDDM likely won't start without elogind. Enable and start it using:

To start the chosen display manager on boot, add the display-manager to the system's default runlevel:

To start the display-manager immediately, run:

systemd

SDDM might not start properly if a machine-id hasn't been generated. To ensure the system has a machine-id:

To start SDDM on boot:

To start SDDM now:

Plasma

Graphical configuration is integrated in Plasma system settings by installing kde-plasma/sddm-kcm :

Troubleshooting

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 sys-apps/haveged 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 Xorg.log log file:

/var/log/Xorg.0.log:[ 2058.998] (EE) /dev/dri/card0: failed to set DRM interface version 1.4: Permission denied
/var/log/Xorg.0.log:[ 2061.229] (EE) intel(0): [drm] failed to set drm interface version: Permission denied [13].

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

Missing system buttons

SDDM only displays buttons if the functionality evaluates to being available. This can depend on several factors. For OpenRC systems using elogind, this can be caused by the service not running when the display manager is initialized. To make sure it is running, just add elogind to the boot run level.

Missing users

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

[Users]
MaximumUid=60000
MinimumUid=1000

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 the kernel. If it isn't, enable it, rebuild the kernel, and re-emerge x11-drivers/nvidia-drivers .

Device Drivers --->
 Graphics support --->
 <*> Direct Rendering Manager (XFree86 4.1.0 and higher DRI support) --->
 [*] Enable legacy fbdev support for your modesetting driver

Ensure the nvidia-drm module is configured to load at startup and modeset option enabled:

nvidia-drm
options nvidia-drm modeset=1

Alternatively, modeset option can be enabled on the kernel command line with nvidia-drm.modeset=1. This can be set in the bootloader or embedded in the kernel configuration.

See also

• LightDM — a cross-desktop display manager whose aim is to be the standard display manager for the X server.
• SLiM — a desktop-independent graphical display manager.

• Display manager