/etc/fonts/local.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
    <alias>
        <family>serif</family>
        <prefer>
            <family>IPAPMincho</family>
            <family>DejaVu Serif</family>
        </prefer>
    </alias>
    <alias>
        <family>sans-serif</family>
        <prefer>
            <family>M+ 1p</family>
            <family>IPAPGothic</family>
            <family>DejaVu Sans</family>
        </prefer>
    </alias>
    <alias>
        <family>monospace</family>
        <prefer>
            <family>M+ 1mn</family>
            <family>IPAPGothic</family>
            <family>DejaVu Sans Mono</family>
        </prefer>
    </alias>
</fontconfig>