Enable/disable KDE 4 desktop effects on command-line

Today I had a problem that my laptop, running KDE4 with desktop effects turned on, froze before I could start systemsettings and disable it. So to manually disable it:
- start Ubuntu in recovery mode
- go to root console
- go to /home/$USER/.kde or /home/$USER/.kde4
- then edit share/config/kwinrc
- set Enabled to false under [Compositing]