Eu uso este conteúdo em ~ / .fonts.conf para substituir várias fontes com o Ubuntu
<!--?xml version="1.0"?>-->
<!--DOCTYPE fontconfig SYSTEM "fonts.dtd">-->
<!-- ~/.fonts.conf for per-user font configuration -->
<fontconfig>
<alias>
<family>sans-serif</family>
<prefer>
<family>Ubuntu</family>
</prefer>
</alias>
<alias>
<family>monospace</family>
<prefer>
<family>Ubuntu Mono</family>
</prefer>
</alias>
<match>
<test name="family"><string>Arial</string></test>
<edit name="family" mode="prepend" binding="strong">
<string>Ubuntu</string>
<string>Arial</string>
</edit>
</match>
<match>
<test name="family"><string>helvetica</string></test>
<edit name="family" mode="prepend" binding="strong">
<string>Ubuntu</string>
<string>Helvetica</string>
</edit>
</match>
</fontconfig>