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# SDDM

From ArchWiki

The Simple Desktop Display Manager (SDDM) is a display manager. It is the recommended display manager for the LXQt desktop environment.

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.

Note As of SDDM version 0.20, Wayland sessions are listed and can be started from SDDM, but the SDDM greeter itself still runs in X11 mode by default, although an experimental Wayland greeter can be enabled.

## Installation

Install the sddm package. Optionally, install sddm-kcm for the KConfig Module and qt5-declarative for enabling Qt5 theme support.

Follow Display manager#Loading the display manager to start SDDM at boot.

## Configuration

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-conf-gitAUR available.

Everything should work out of the box, since Arch Linux uses systemd and SDDM defaults to using `systemd-logind` for session management.

### Autologin

SDDM supports automatic login through its configuration file, for example:

    /etc/sddm.conf.d/autologin.conf

    [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.

To autologin into KDE Plasma while simultaneously locking the session (e.g. to allow autostarted apps to warm up), see KDE#Lock screen.

### Passwordless login

It is possible to configure SDDM to allow logging into some accounts without a password. This differs from automatic login in that the user still has to choose which account to log into, and it differs from simply setting the account password to the empty string in that it only allows interactive users to log in (and not, for example, remote users logged in via SSH).

SDDM goes through PAM so you must configure the SDDM configuration of PAM:

    /etc/pam.d/sddm

    #%PAM-1.0
    auth        sufficient  pam_succeed_if.so user ingroup nopasswdlogin
    auth        include     system-login
    ...

In order to also allow unlocking the KDE Plasma lock screen without a password, also add the same line at the top of `/etc/pam.d/kde`:

    /etc/pam.d/kde

    #%PAM-1.0
    auth        sufficient  pam_succeed_if.so user ingroup nopasswdlogin
    auth        include     system-login
    ...

You must then also be part of the `nopasswdlogin` group to be able to login interactively without entering your password:

    # groupadd -r nopasswdlogin
    # gpasswd -a username nopasswdlogin

### Unlock KDE Wallet automatically on login

See KDE Wallet#Unlock KDE Wallet automatically on login.

### Theme settings

Theme settings can be changed in the `[Theme]` section. If you use Plasma's system settings, themes may show previews.

Set to `breeze` for the default Plasma theme.

Some themes are available in the AUR, for example archlinux-themes-sddmAUR.

#### Current theme

Set the current theme through the `Current` value, e.g. `Current=archlinux-simplyblack`.

#### Editing themes

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:

    /usr/share/sddm/themes/name/theme.conf.user

    [General]
    background=/path/to/background.png

#### 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-qt6 --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.

Note This is just a preview. In this mode, some actions like shutdown, suspend or login will have no effect.

#### Mouse cursor

To set the mouse cursor theme, set `CursorTheme` to your preferred cursor theme.

Valid Plasma mouse cursor theme names are `breeze_cursors`, `Breeze_Light` and `breeze-dark`.

In case SDDM defaults to the Adwaita theme on KDE setups (GNOME mouse cursor), one should set the `Inherits` variable to the desired value in `/usr/share/icons/default/index.theme` manually.

Tip On Plasma, run `grep -i cursortheme ~/.config/kcminputrc` to check the name of the active mouse cursor theme.

#### User icon (avatar)

This article or section is out of date.

Reason: SDDM detects icons in `/var/lib/AccountsService/icons/` without configuration and Plasma no longer creates the files in `$HOME/`. (Discuss in Talk:SDDM)

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 `/etc/sddm.conf.d/avatar.conf`.

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 `FacesDir` is `/usr/share/sddm/faces/`. You can change the default `FacesDir` location to suit your needs. Here is an example:

    /etc/sddm.conf.d/avatar.conf

    [Theme]
    FacesDir=/var/lib/AccountsService/icons/

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).

Note In many KDE versions, the user icon image file is `~/.face` and `~/.face.icon` is 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.

### Numlock

If you want to enforce numlock to be enabled, set `Numlock=on` in the `[General]` section.

If SDDM is running under Wayland, the numlock setting currently does not work. You may need to change KWin settings to enable it, see this issue.

### Rotate display

See Xrandr#Configuration.

### DPI settings

Sometimes it is useful to set up the correct monitor's PPI settings on a "Display Manager" level.[1] To do so you need to add to `ServerArguments` the parameter `-dpi your_dpi` at the end of the string. For example:

    /etc/sddm.conf.d/dpi.conf

    [X11]
    ServerArguments=-nolisten tcp -dpi 94

### Enable HiDPI

Note Since sddm version 0.20.0, HiDPI support is enabled by default, and the following step is not necessary.

Create the following file:

    /etc/sddm.conf.d/hidpi.conf

    [Wayland]
    EnableHiDPI=true

    [X11]
    EnableHiDPI=true

When using Wayland, the HiDPI scaling depends on the greeter used.[2] For instance, when using a Qt-based greeter such as Breeze, add the following configuration:

    [General]
    GreeterEnvironment=QT_SCREEN_SCALE_FACTORS=2,QT_FONT_DPI=192

### Enable virtual keyboard

Install qt6-virtualkeyboard (or another virtual keyboard).

Create the following file:

    /etc/sddm.conf.d/virtualkbd.conf

    [General]
    InputMethod=name_of_virtual_keyboard

SDDM now displays a button in lower-left corner of login screen to open the virtual keyboard.

### Using a fingerprint reader

Tip KDE's lock screen should already support unlocking with fprint since the release of Plasma 6, `kscreenlocker` ships with the required `/etc/pam.d/kde-fingerprint`.

But that configuration does not include login, only unlocking of existing sessions.

Because KWallet requires passwordbased auth on login (see below), you might still want to skip the setup for fprint with SDDM.

Note Make sure that your fingerprint is registered before making these changes. Fingerprint support is not completely working properly yet, and it seems logging in with only a password no longer works using this method.

SDDM works with a fingerprint reader when using fprint. After installing fprint and adding fingerprint signatures, add the following to the top of `/etc/pam.d/sddm`:

    /etc/pam.d/sddm

    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:

    /etc/pam.d/sddm

    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.

If you now press enter in the empty password field, the fingerprint reader should start working.

### Rootless

Traditionally, the X11 display server has been run with root privileges by default. This rootful mode allows X11 to have unrestricted access to system resources, which was necessary for its operation in environments where direct hardware access and management were common. However, with the increasing emphasis on security in modern computing environments, efforts have been made to transition to rootless modes, which is also why Wayland by default runs in rootless mode.

Starting unprivileged X11 (and Wayland) sessions has been supported since sddm 0.20.0.[3]

To enable rootless mode: create a new configuration file under `/etc/sddm.conf.d/`, name it something meaningful, and add the following to it, replacing `x11-user` with `wayland` if necessary.

    /etc/sddm.conf.d/rootless-x11.conf

    [General]
    DisplayServer=x11-user

To confirm whether you are running in rootless mode check which user owns the compositor process (e.g. `kwin_wayland`)

### Wayland

Note

- SDDM considers its Wayland support experimental.
- By default `DisplayServer=wayland` attempts to use the weston compositor, even if it's not installed, to use a different Wayland compositor, enter the program and relevant arguments to the `CompositorCommand` option as described in #KDE Plasma / KWin, see also sddm.conf(5) for more.

#### KDE Plasma / KWin

Adding the following lines to your configuration file sets the Wayland compositor to KWin and enables the wlr_layer_shell Wayland protocol extension. This requires layer-shell-qt and layer-shell-qt5AUR for SDDM themes using Qt6 and Qt5, respectively.

    /etc/sddm.conf.d/10-wayland.conf

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

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

##### Virtual keyboards

To enable virtual keyboard support (e.g. using qt6-virtualkeyboard or plasma-keyboard), append the `--inputmethod` flag with the appropriate keyboard to the `kwin_wayland` command as shown below. Do not set the option `InputMethod` in the section `General`, since this will cause the virtual keyboard to no longer be shown.

    /etc/sddm.conf.d/10-wayland.conf

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

##### Match Plasma display configuration

Changes to your display configuration made in a Plasma Wayland session (e.g. monitor layout, resolution, etc) will not persist to SDDM. To make them persist open Plasma's System Settings and navigate to Colors & Themes > Login Screen (SDDM) and click "Apply Plasma Settings...". You will need to have permission to perform this action.

The same can be achieved manually with the following:

To enable correct display & monitor handling in SDDM (scaling, monitor resolution, hz,...), you can copy or modify the appropriate configuration file from your home directory to the one of SDDM:

    # cp ~/.config/kwinoutputconfig.json /var/lib/sddm/.config/
    # chown sddm:sddm /var/lib/sddm/.config/kwinoutputconfig.json

To also enable correct input handling in SDDM (tap-to-click, touchscreen mapping,...), you can copy the appropriate configuration file from your home directory to the one of SDDM:

    # cp ~/.config/kcminputrc /var/lib/sddm/.config/
    # chown sddm:sddm /var/lib/sddm/.config/kcminputrc

## Troubleshooting

### Blank screen with cursor, but no greeter shows

Greeter crashes if there is no available disk space. Check your disk space with `df -h`.

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.

### Hangs after login

Try removing `~/.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.

Note that the config file still has the option `MinimumVT` but is ignored since SDDM version 0.20: sddm.conf(5) § MinimumVT=.

### One or more users do not show up on the greeter

Warning Users set with a UID lower than 1000 or higher than 60513 should generally not be exposed to a display manager.

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:

    /etc/sddm.conf.d/uid.conf

    [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:

    /etc/sddm.conf.d/avatars.conf

    [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 [4]. This seems to not be a bug in SDDM but in X server.[5]

### Screen resolution is too low

Issue may be caused by HiDPI usage for monitors with corrupted EDID [6]. 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:

    /etc/X11/xorg.conf.d/90-monitor.conf

    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:

    /etc/sddm.conf.d/avatar.conf

    [Theme]
    EnableAvatars=false

### X authority (aka MIT-MAGIC-COOKIE) file

SDDM uses a random fresh UUID for the auth file as described in details at [7]. 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:

    /usr/share/sddm/scripts/Xsetup

    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

Note xrandr will give differing names for outputs in a Wayland session. Ensure you're in a X11 session before running the above command.

The following Xsetup recreates the above setup for the login window:

    /usr/share/sddm/scripts/Xsetup

    #!/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

### 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.

### Failing first password attempt results in text clearing itself after a few keystrokes on subsequent attempts

Use a different theme than the default.

### Screen out of sync on hybrid graphics with Wayland

If you set up SDDM with `kwin_wayland` compositor, one may encounter a screen out of sync when booting. If returning back to X11 works well, and you're using `mesa-amber` drivers, chances are Wayland will work well by just replacing your current `mesa-amber` drivers with `mesa`. You can find more details about this issue at KDE Bug 483804.

### Some themes crash

Some SDDM themes do not specify `QtVersion` in `metadata.desktop` and SDDM starts with incompatible greeter (qt5 instead of qt6).

If you have set custom theme but on reboot there is default theme with error `Library import requires a version`, you need to add `QtVersion=6` to `/usr/share/sddm/themes/ThemeName/metadata.desktop`.

### 12h or 24h clock

You could see an SDDM with a 12hr (am/pm) clock where you would expect a 24h clock. This is more likely for people who use a non-native language (like french people using US English) but still expecting units to be in their local format.

This behavior is not determined by SDDM settings, but in `/etc/locale.conf`. Make sure you have an `LC_TIME` set with the locale of choice. See Locale for details.

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