I previously wrote about running apps as root on a normal user’s desktop. I still recommend that you follow those steps, but one thing has changed with the release of karmic and the inclusion of the qtcurve widget style.
Unlike the now deprecated gtk-qt widget style, qtcurve doesn’t let you configure anything. It directly reads your preferences from KDE and uses those. In particular, it uses your “General” font setting from KDE Control Centre -> Appearance -> Fonts.
There is a bug with qtcurve which causes it to have big fonts by default. A fix can be found in my last post.
If you use qtcurve, the GUI style won’t apply to your applications running as root. This is because qtcurve doesn’t respect the contents of ~/.gtkrc-2.0 (normally where GTK engines look for customisations). It instead reads your ~/.kde/share/config/kdeglobals file.
So if you want your root applications to look like your normal applications, first fix qtcurve as above. Then copy your kdeglobals to root:
sudo cp ~/.kde/share/config/kdeglobals /root/.kde/share/config/kdeglobals
You’ll have to repeat this if you change your “General” font setting. Don’t symlink to your file, as this may cause it to be owned by root next time you run an application as root.