changing Application Fonts for debian

[Basanta Shrestha <basanta mpp org np>]

Dear List,
We are localizing gnome. I have added a font. There is no problem in 
manually changing this font for 'Application Font', 'Desktop Font' and 
'Window Title font'. But I need to be make this font one and the only 
default font so that this font is used across whole gnome application 
interfaces. Please note that I can NOT use gui to do this!! Can any one 
tell me how to do this by directly modifying into files? This font 
should be used for all the login users that exists in the system.
o/s:  Debian linux

-basanta