Not able to logout ( shutudown or sleep too ) of KDE Desktop
 

When I want to logout, shutdown or use sleep, nothing happens. I have to press the power if I want to turn the computer off. Thanks.

Your sidebar indicates that you are using Slackware.

By default, in Slackware, you login to the command line, then issue "startx" to start the GUI. You exit the GUI to the command line, then issue the shutdown command as root ("shutdown now -h") (granted, there are other ways to do it, but this is one). What happens when you do this?

(Of course, you can issue the shutdown command from a terminal as root while still in the GUI. In Linux, there are often many roads to Rome.)

Please provide more information. Are you booting to the command line or are you booting to a graphical interface (runlevel 4)? What make/model computer are you using? What is the output of the command

issued in a terminal?

With enough information, we should be able to figure this out.

This shouldn't happen for logout, but IIRC your user needs to be in the power group to be able to shutdown the system or put it into standby/hibernate mode.