/etc/X11/app-defaults/XDu is in xdu 3.0-18.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | !
! XDu Resources
!
! I recommend the "-*-helvetica-bold-r-normal--14-*" font, but if
! you don't have it, or want your server default, then change it
! or comment it out respectively.
! Order choices: first, last, alpha, ralpha, size, rsize
! Color to taste.
!
!*foreground: yellow
!*background: blue4
!*help*foreground: green
!*help*background: red4
*window.Width: 600
*window.Height: 480
!*Font: -*-helvetica-bold-r-normal--14-*
!*Ncol: 5
!*ShowSize: true
!*Order: first
|