The X Core Font System is a very old font system of the X Window Server (some of the man pages are 25 years old!). However, some things (most notably bar ain’t recursive) still use it.

The default installed fonts for the Core Font System aren’t very nice, and I wanted to use my own. Fortunately, it not only has support for TrueType fonts (wow), but it’s very easy add them:

• Navigate to the directory containing the fonts (e.g. /usr/share/fonts/truetype/ubuntu-font-family/)
• Run mkfontscale then mkfontdir (you may need to install something like xfonts-utils)
• Add something like xset fp+ /usr/share/fonts/truetype/ubuntu-font-family/ to your ~/.xinitrc file