The Simple Desktop Display Manager (SDDM) is a display manager. It is the recommended display manager for the KDE Plasma and LXQt desktop environments.
From Wikipedia:Simple Desktop Display Manager:
- Simple Desktop Display Manager (SDDM) is a display manager (a graphical login program and session manager) for the X11 and Wayland windowing systems. SDDM was written from scratch in C++11 and supports theming via QML.
The KDE development team has accepted a proposal to incorporate the SDDM project into the Plasma Desktop project. SDDM will be an official part of Plasma and updates will likely be pushed alongside Plasma Desktop updates.
Install the sddm package. Optionally install sddm-kcm for the KConfig Module.
Follow Display manager#Loading the display manager to start SDDM at boot.
The default configuration file for SDDM can be found at
/usr/lib/sddm/sddm.conf.d/default.conf. For any changes, create configuration file(s) in
/etc/sddm.conf.d/. See sddm.conf(5) for all options.
The sddm-kcm package (included in the plasma group) provides a GUI to configure SDDM in Plasma's system settings. There is also a Qt-based sddm-config-editor-gitAUR available.
Everything should work out of the box, since Arch Linux uses systemd and SDDM defaults to using
systemd-logind for session management.
SDDM supports automatic login through its configuration file, for example:
[Autologin] User=john Session=plasma
This configuration causes a KDE Plasma session to be started for user
john when the system is booted. Available session types can be found in
/usr/share/xsessions/ for X and in
/usr/share/wayland-sessions/ for Wayland.
An option to autologin into KDE Plasma while simultaneously locking the session is not available 
You can add a script that activates the screensaver of KDE to the autostart as a workaround:
#!/bin/sh /usr/bin/dbus-send --session --type=method_call --dest=org.freedesktop.ScreenSaver /ScreenSaver org.freedesktop.ScreenSaver.Lock &
Unlock KDE Wallet automatically on login
See KDE Wallet#Unlock KDE Wallet automatically on login.
Theme settings can be changed in the
[Theme] section. If you use Plasma's system settings, themes may show previews.
breeze for the default Plasma theme.
Some themes are available in the AUR, for example archlinux-themes-sddmAUR.
Set the current theme through the
Current value, e.g.
The default SDDM theme directory is
/usr/share/sddm/themes/. You can add your custom made themes to that directory under a separate subdirectory. Note that SDDM requires these subdirectory names to be the same as the theme names. Study the files installed to modify or create your own theme.
Customizing a theme
To override settings in the
theme.conf configuration file, create a custom
theme.conf.user file in the same directory. For example, to change the theme's background:
Testing (previewing) a theme
You can preview an SDDM theme if needed. This is especially helpful if you are not sure how the theme would look if selected or just edited a theme and want to see how it would look without logging out. You can run something like this:
$ sddm-greeter --test-mode --theme /usr/share/sddm/themes/breeze
This should open a new window for every monitor you have connected and show a preview of the theme.
To set the mouse cursor theme, set
CursorTheme to your preferred cursor theme.
Valid Plasma mouse cursor theme names are
User icon (avatar)
SDDM reads the user icon (a.k.a. "avatar") as a PNG image from either
~/.face.icon for each user, or the common location for all users specified by
FacesDir in an SDDM configuration file. The configuration setting can be placed in either
/etc/sddm.conf directly, or, better, a file under
/etc/sddm.conf.d/ such as
To use the
FacesDir location option, place a PNG image for each user named
username.face.icon at the location specified by the
FacesDir key in the configuration file. The default location for
/usr/share/sddm/faces/. You can change the default
FacesDir location to suit your needs. Here is an example:
The other option is to put a PNG image named
.face.icon at the root of your home directory. In this case, no changes to any SDDM configuration file is required. However, you need to make sure that
sddm user can read the PNG image file(s) for the user icon(s).
~/.face.iconis a symlink to that file. If the user icon images are symlinks, you need to set proper file permissions to the target files.
To set proper permissions run:
$ setfacl -m u:sddm:x ~/ $ setfacl -m u:sddm:r ~/.face.icon
You can check permissions with:
$ getfacl ~/ $ getfacl ~/.face.icon
See SDDM README: No User Icon.
If you want to enforce Numlock to be enabled, set
Numlock=on in the
Sometimes it is useful to set up the correct monitor's PPI settings on a "Display Manager" level. To do so you need to add to
ServerArguments the parameter
-dpi your_dpi at the end of the string. For example:
[X11] ServerArguments=-nolisten tcp -dpi 94
Create the following file:
[Wayland] EnableHiDPI=true [X11] EnableHiDPI=true
Enable virtual keyboard
Create the following file:
SDDM now displays a button in lower-left corner of login screen to open the virtual keyboard.
Using a fingerprint reader
SDDM works with a fingerprint reader when using fprint. After installing fprint and adding fingerprint signatures, add the following to the top of
auth sufficient pam_fprintd.so
In order to use either a password or a fingerprint, you can instead add the following to the top of the file:
auth [success=1 new_authtok_reqd=1 default=ignore] pam_unix.so try_first_pass likeauth nullok auth sufficient pam_fprintd.so
Note that KWallet cannot be unlocked using a fingerprint reader (see KDE Wallet#Unlock KDE Wallet automatically on login), but the first line ensures that a password login will automatically unlock KWallet.
auth sufficient pam_unix.so try_first_pass likeauth nullok auth sufficient pam_fprintd.so
The first line looks different from the corresponding
/etc/pam.d/sddm configuration because the KDE lock screen does not need to run the KWallet pam module.
If you now press enter in the empty password field, the fingerprint reader should start working.
Running under Wayland
SDDM can run rootless under Wayland, but currently only when using the sddm-gitAUR package.
Create a new config file in the
/etc/sddm.conf.d/ directory, name it something like
Add the following to the new file:
[General] DisplayServer=wayland GreeterEnvironment=QT_WAYLAND_SHELL_INTEGRATION=layer-shell [Wayland] CompositorCommand=
Next, you will need a Wayland compositor (such as KDE's KWin compositor) to render SDDM, and enter the program and relevant arguments as a parameter to
KDE / KWin
Add the following as a parameter to
CompositorCommand into the SDDM config file created above (e.g
[Wayland] CompositorCommand=kwin_wayland --no-lockscreen
To enable virtual keyboard support (e.g. using qt5-virtualkeyboard or maliit-keyboard), append the
--inputmethod flag with the appropriate keyboard to the
kwin_wayland command, like so (replacing
qtvirtualkeyboard as necessary):
[Wayland] CompositorCommand=kwin_wayland --no-lockscreen --inputmethod maliit-keyboard
Blank screen with cursor, but no greeter shows
Greeter crashes if there is no available disk space. Check your disk space with
If disk space is not the issue, it may be due to a bug. Switch to another TTY, and then try
loginctl unlock-session session_id or to restart SDDM.
Long load time before SDDM shows the greeter
A low entropy pool can cause long SDDM load time (Bug report). See Random number generation for suggestions to increase the entropy pool.
Hangs after login
~/.Xauthority and logging in again without rebooting. Rebooting without logging in creates the file again and the problem will persist.
SDDM starts on tty1 instead of tty7
SDDM follows the systemd convention of starting the first graphical session on tty1. If you prefer the old convention where tty1 through tty6 are reserved for text consoles, change the default value of
MinimumVT variable, which comes under the
One or more users do not show up on the greeter
By default, SDDM is configured to displays only users with a UID in the range of 1000 to 60513. If the UIDs of the desired users are outside this range then you will have to modify the range.
For example, for a UID of 501, set
MinimumUid and hide those with shells used by system users:
[Users] HideShells=/usr/bin/nologin,/sbin/nologin,/bin/false,/usr/bin/git-shell MinimumUid=500
For users with a higher UIDs, set
MaximumUid to the appropriate value.
User avatars do not show up on the greeter
User avatars are not shown on the greeter if the number of users exceeds
DisableAvatarsThreshold parameter or if avatars are not enabled at all as controlled by
EnableAvatars parameter. To circumvent this add the following lines to your sddm configuration:
[Theme] EnableAvatars=true # enable avatars DisableAvatarsThreshold=7 # set the threshold for the number of users. Avatars are not shown if this threshold is exceeded.
SDDM loads only US keyboard layout
SDDM loads the keyboard layout specified in
/etc/X11/xorg.conf.d/00-keyboard.conf. You can generate this configuration file by
localectl set-x11-keymap command. See Keyboard configuration in Xorg for more information.
An alternative way of setting the keyboard layout that will only set it in SDDM and not subsequent sessions is to invoke a setxkbmap command in the startup script of SDDM, located at
/usr/share/sddm/scripts/Xsetup. See Xorg/Keyboard configuration#Using setxkbmap for examples.
SDDM may also incorrectly display the layout as US but will immediately change to the correct layout after you start typing your password . This seems to not be a bug in SDDM but in X server.
Screen resolution is too low
Issue may be caused by HiDPI usage for monitors with corrupted EDID . If you have enabled HiDPI, try to disable it.
If even the above fails, you can try setting your screen size in a Xorg configuration file:
Section "Monitor" Identifier "<default monitor>" DisplaySize 345 194 # in millimeters EndSection
Long load time on autofs home directory
SDDM by default tries to display avatars of users by accessing
~/.face.icon file. If your home directory is an autofs, for example if you use dm-crypt, this will make it wait for 60 seconds, until autofs reports that the directory cannot be mounted.
You can disable avatars by creating the following configuration file:
SDDM uses a random fresh UUID for the auth file as described in details at . So in order to find that file one may use a script:
# find /var/run/sddm/ -type f
This may be needed if one needs to start x11vnc when there is no user logged in. For example:
# x11vnc -display :0 -auth "$( find /var/run/sddm/ -type f )"
Overlapping greeters on multiscreen setup
It happens that the X monitor layout is not setup correctly on multiscreen setup leading to overlapping greeters. To solve this add the following lines to order your sddm greeter layout from left to right:
for next in $(xrandr --listmonitors | grep -E " *[0-9]+:.*" | cut -d" " -f6); do [ -z "$current" ] && current=$next && continue xrandr --output $current --auto --output $next --auto --right-of $current current=$next done
Login session appears on an unexpected display
It can happen that the SDDM login session appears on a different display than your primary display if multiple displays are connected. This problem can be annoying if the secondary display is rotated and the primary display is not. A simple fix to this problem is to use xrandr to configure the displays before the login session using Xsetup script. E.g. here xrandr reports that there are two connected displays where the secondary display (DP-2) is left of the primary display (DP-4).
# xrandr | grep -w connected 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 following Xsetup recreates the above setup for the login window:
#!/bin/sh # Xsetup - run as root before the login dialog appears xrandr --output DP-4 --auto --primary xrandr --output DP-2 --left-of DP-4 --rotate left --noprimary
KDE Plasma Wayland hangs on shutdown and reboot
In some cases on KDE Plasma Wayland sessions, SDDM (release 0.19.0-9) does not stop when issuing a shutdown or a reboot. This results in the shutdown process hanging while systemd waits for SDDM to stop. This bug has already been fixed, but until a new version of SDDM is released, there are a few possible workarounds:
- Install sddm-gitAUR, which includes the commits fixing the problem
- While the shutdown process is hanging, pressing
Ctrl+Alt+F1to switch to the SDDM tty will allow SDDM to stop properly
- Logging out from Plasma and then shutting down or rebooting from SDDM will also work properly
- By default systemd waits 90s before forcibly terminating SDDM with a SIGKILL, but you can lower that time threshold by editing the service
sddm.servicewith a drop-in file.
For more information about the bug see  and .
Black screen after logout with NVIDIA graphics card
One may encounter a complete black screen or with only cursor/display device logo on it after the logout of any user. This happens because
sddm.service starts faster than the NVIDIA drivers. Consider using early KMS.