after using Dexter I get a configuration which contains:
FontPath "unix:/7100" # local font server
# if the local font server has problems, we can fall back on these
but I don't have xfonts-100dpi installed, only xfonts-75dpi.
Arround line 335 of dexter it reads:
"NetMousePS/2" "Genius NetMouse or NetMousePro" \
this is the protocol I need to use, yet my mouse is a Logitech one.
The generated config file load every module on the system, including
the dri one, which needs this somewhere:
Mode 0666 means anyone with a current connection to the X server can
create a direct rendering context. You can specify a Group and use mode
0660 instead, but doesn't make sense on a default Debain installation.