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I'm giving KDE another try - so far so good. I installed everything using apt-get install kubuntu-desktop. During the installation it asked me which login manager to use and I chose LightDM - however, now I'm finding user sessions (KDE) are behaving a little funny - when left for some time, they lock out asking for password, but there's no way to switch user (i.e. there's a small window asking for password with Ok and Cancel buttons - no Switch User, Shutdown, Suspend or anything).

Pressing Ctrl-Alt-F[something] shows a text log, where I can see a message "Not starting KDM because it's not the default manager" - so I think my problem can be fixed by making it default.

How can I do this?

(actually, trying to switch user via K-menu - Leave - Switch user results in the same dialog: "The session was locked by sergey, please enter your password")

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3 Answers 3

up vote 17 down vote accepted


With the Debian and the Debian based (K/X/L/ubuntu) you could use the dpkg-reconfigure.

    man dpkg-reconfigure:

           dpkg-reconfigure - reconfigure an already installed package

            dpkg-reconfigure [options] packages

    dpkg-reconfigure reconfigures packages after they have already been 
    installed. Pass it the names of a package or packages to reconfigure. 
    It will ask configuration questions, much like when the package was first installed...

That is:

sudo dpkg-reconfigure kdm


sudo dpkg-reconfigure gdm

or ...

Kubuntu & LightDM

The LightDM is :

There was a plan:


With the Oneiric the Kubuntu desktop is depending the KDM:

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Note that when you run the reconfigure command on either gdm or kdm, you have to choose between the two display managers yourself. – Thomas W. Oct 21 '11 at 18:19
If there is only one display manager installed, the dpkg-reconfigure command will have no output. – systemovich Nov 17 '14 at 8:09

Solution that doesn't require root access

Make a file ~/.xinitrc:

# makes a kde a default desktop after `startx':
exec startkde

Also make ~/.xsession:

# makes a kde a default desktop after `xdm':
exec startkde
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Have been looking for this solution since yesterday. I am not sure what I do, my startx always bring me to WindowMaker. Now I am returning back to KDE ;) – swdev Feb 19 '14 at 13:21

please have a look at the following file:


There you can change to kdm.

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This is also a valid answer although dpkg-reconfigure is probably more foolproof. – Sergey Oct 21 '11 at 20:37

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