[OS X TeX] sudo ln -s /opt/X11 /usr/X11

[Richard Koch]

Shen,

Recently third parties took over the maintenance of X11. So upgrading OS X sometimes
removes X11, replacing it with a stub. It is easy to locate XQuartz on the network 
and reinstall X for OS X.

TeX Live is compiled with X11 active. I can imagine the warning you report when X11 isn’t
available, but I expect pdflatex to work anyway. I haven’t heard of a case of pdflatex
actually failing to work when X11 is missing.

When you install XQuartz, it puts X11 libraries in /opt even though the Mac expects
to find them in /usr/X11. I thought it automatically created symbolic links, but maybe not.
The advice you were given created the symbolic links, but without putting the
expected libraries in /opt. Not very reasonable..

My advice:

	Don’t worry about an X11 warning unless it actually causes a Latex error.

	In case of an error, just install XQuartz

Dick Koch