From Fedora Project Wiki

SDDM as the default KDE display manager instead of KDM


Retire KDM as the default display manager of the KDE Fedora Spin in favor of SDDM.


  • Name:
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  • IRC: #fedora-kde

Current status

Detailed Description

As described in many articles and discussions, KDM is nearing its end of life and it's time we decided upon the successor.

I'm proposing to switch to SDDM, which is a new project that suits our needs perfectly despite its immaturity:

As of July 2013, KDM's maintenance consists of bugfixes for the most painful bugs, consisting of only about 20 actual commits to the repository in last two years (excluding translation, themes and merges), adding many new features would require major changes to a lot of the code and there is no active maintainer.

SDDM is written in C++11/Qt5 (compared to the bits of XDM in KDM), compilable against Qt4, supports QtQuick theming and its upstream is quite active.

Compared to the current DM, KDM, it currently lacks a few features (such as XDMCP) but adds some other ones (QtQuick themes) or is currently adding them (Keyboard layout switching in the greeter).

Benefit to Fedora

We'll lead the way for other distributions in terms of which DM to provide for KDE Frameworks 5' / Plasma 2.

Instead of bugreports for obsolete and unmaintainable KDM we'll be getting bugreports for fresh SDDM with clean codebase


  • Proposal owners:
    • Fix the bugs affecting log in: PAM stack integration and LDAP user lists
    • Change kde-settings and the spin-kickstarts to provide SDDM package instead of KDM
    • (eventually) exclude KDM from the kde-workspace package
  • Other developers: N/A (not a System Wide Change)
  • Release engineering: N/A (not a System Wide Change)
  • Policies and guidelines: N/A (not a System Wide Change)

Upgrade/compatibility impact

Previous versions of Fedora won't be impacted by this change. Their users will have the possibility to switch from whichever DM they were using to SDDM.

SDDM is now lacking some functionality compared to KDM, namely XDMCP, VNC and multi-seat support. They are planned to be added.

How To Test

Anybody able to run KDE Plasma Workspaces as his desktop can test.

System preparation

  • Create some testing users
for i in test1 test2 test3; do useradd --password test $i; done
  • Install and enable SDDM
yum install sddm # when the packages are included in the repositories)
systemctl enable --force sddm.service

Basic testing

(basically applies to every DM/DE combination)

1. Log in as test1

2. From the Kickoff menu, select Leave > Switch User > New Session.

  • SDDM greeter should appear

3. Repeat steps 1. and 2. for users test2 and test3

4. Try switching the sessions (VTs) with [Ctrl+Alt+F<x>] keys.

  • test1 should be on VT1 ([Ctrl+Alt+F1]), test2 on VT2 and so on.

5. Try switching the sessions using the Leave > Switch User dialog.

6. Log out user test2 and switch to test1, then use the Leave -> Switch User dialog to switch to test3.

7. Use the Leave > Switch User > New Session dialog to log test2 again.

Please report any deviations from the expected usual multi-user desktop experience.

Further tests

Also, please test using your regular workflow, especially if your computer is used by more than a single user.

If you're a user of some of the special authentication methods (such as a central authentication server, or a fingerprint reader), please test logging in while using them, too, and report the results to us.

User Experience

KDE Spin login screen's appearance changes.

Login screen configuration menu in systemsettings will be different (upstream provides its own KCM module)

KDM will still be included in the repositories with further updates, allowing the user to switch to it at his option.


Only dependent package will be sddm-kcm, providing the configuration module for SDDM.

Coordination with other maitainers won't be necessary now. However it is possible other DEs will decide to use SDDM as their default DM in future releases.

Contingency Plan

  • Contingency mechanism: Continue to use KDM as the default KDE Spin display manager.
  • Contingency deadline: Beta freeze
  • Blocks release? Depends on the state of the feature. If some basic functionality of a display manager is missing, we'll have to revert to KDM.



Release Notes

KDE spin of Fedora now uses SDDM as its new default display manager. KDM (the previous one) is still available for installation from the Fedora repositories.

If you want to return to KDM usage, install it by using yum install kdm and enable the service with systemctl enable --force kdm.service.