the problem with installing ntop on freebsd

mail# cd /usr/ports/net/ntop
mail# make install clean
===> Installing for ntop-3.3_1
===> ntop-3.3_1 depends on executable: dot - not found
===> Verifying install for dot in /usr/ports/graphics/graphviz
===> graphviz-2.14.1_1 depends on executable: wish8.4 - found
===> graphviz-2.14.1_1 depends on executable: gmake - found
===> graphviz-2.14.1_1 depends on executable: bison - found
===> graphviz-2.14.1_1 depends on file: /usr/local/bin/libtool - found
===> graphviz-2.14.1_1 depends on file: /usr/local/libdata/xorg/libraries - not found
===> Verifying install for /usr/local/libdata/xorg/libraries in /usr/ports/x11/xorg-libraries
/usr/X11R6 exists, but it is not a symlink. Installation cannot proceed.
This looks like an incompletely removed old version of X. In the current version, /usr/X11R6 must be a symlink if it exists at all.Please read /usr/ports/UPDATING (entry of 20070519) for the procedure to upgrade X.org related ports.*** Error code 1

Stop in /usr/ports/x11/xorg-libraries.
*** Error code 1

Stop in /usr/ports/graphics/graphviz.
*** Error code 1

Stop in /usr/ports/net/ntop.
*** Error code 1

Stop in /usr/ports/net/ntop.
mail# rm /usr/X11R6/

*********
from the error messages:
usr/X11R6 exists, but it is not a symlink. Installation cannot proceed.

This looks like an incompletely removed old version of X. In the
current version, /usr/X11R6 must be a symlink if it exists at
all.Please read /usr/ports/UPDATING (entry of 20070519) for the
procedure to upgrade X.org related ports

SO WE SHOULD REMOVE THE sysmlink /usr/X11R6

>rm -r /usr/X11R6
本文出自 “doff” 博客，谢绝转载！