KDM

Summary
Provides an overview of the default display manager for the KDE.
Related
Display Manager

1 Introduction

KDM (KDE Display Manager) is the login manager of KDE. It supports themes, auto-logging, session type choice, and numerous other features.

2 Installation

Install the kdebase-workspace package:

# pacman -S kdebase-workspace

3 Configuration

An example configuration for KDM can be found at /usr/share/config/kdm/kdmrc. See /usr/share/doc/HTML/en/kdm/kdmrc-ref.docbook for all options.

You can visit System Settings > Login Screen and make your changes. Whenever you press "Apply", a KDE Polkit authorization window appears which will ask you to give your root password in order to finish the changes.

If you seem not to be able to edit KDM's settings when launching System Settings as user, you can use kdesu:

$ kdesu kcmshell4 kdm

In the pop-up kdesu window, enter your root password and wait for System Settings to be launched. Then go to Login Screen.

Note: Since you have launched it as root, be careful when changing your settings. All settings configuration in root-launched System Settings are saved under /root/.kde4 and not under ~/.kde4 (your home location).

3.1 Themes

Many KDM 4 themes are available at http://kde-look.org/index.php?xcontentmode=41. Choose between the installed themes in System Settings (run as root) as described above.

3.2 Themes creation

Themes files are in /usr/share/apps/kdm/themes.

The theme format is the same one as GDM, a documentation can be found here: Detailed Description of Theme XML format.

3.3 Configuration file

The master configuration file is /usr/share/config/kdm/kdmrc. The default file contains comprehensive comments about the function of each item.

3.3.1 ServerArgsLocal

To force the number of dots per inch of the X server, add a -dpi option to ServerArgsLocal. A commonly used value is 96 dpi.

ServerArgsLocal=-dpi 96 -nolisten tcp

3.3.2 SessionsDirs

This variable stores a list of directories containing session type definitions in .desktop format, ordered by falling priority. In Parabola some window managers install such files in /usr/share/xsessions. Add that to the list in order to be able to select them in KDM.

SessionsDirs=/usr/share/config/kdm/sessions,/usr/share/apps/kdm/sessions,/usr/share/xsessions

3.3.3 Session

The Session variable is the name of a program which is run as the user who logs in. It is supposed to interpret the session argument (see SessionsDirs) and start the session as desired for that argument. One may wish to customize this for window manager sessions, for example to set a wallpaper and start a screensaver. To do this in a way which will survive pacman updates (which clobber Xsession) do as follows:

cp /usr/share/config/kdm/Xsession /usr/share/config/kdm/Xsession.custom

In kdmrc set

Session=/usr/share/config/kdm/Xsession.custom

And then edit Xsession.custom as desired.

3.3.4 Restart X server menu option

To allow users to restart the X server from KDM, edit this option in kdmrc:

 [X-:*-Greeter]
 # [...]
 # Show the "Restart X Server"/"Close Connection" action in the greeter.
 # Default is true
 AllowClose=true

This feature will be available in the menu drop-down options. The option also includes a hotkey of Alt-E.

4 Troubleshooting

4.1 Keyboard maps

KDM depends on Xorg for keyboard input so if you do not have the good keymap check your xorg.conf file.

See the Xorg article for instructions.

4.2 Slow KDM Start

If KDM is taking a long time (in my case, it was 15-30 seconds) to display the login screen, you can try running the following command as root:

# fc-cache -fv

This will rebuild the X font caches, and may make KDM display the login screen quickly again.

5 Acknowledgement

This wiki article is based on ArchWiki. We may have removed non-FSDG bits from it.