I have spent quite a bit of time figuring out automounts of NFS shares in OS X...
Somewhere along the line, Apple decided allowing mounts directly into /Volumes should not be possible:
/etc/auto_master (see last line):
#
# Automounter master map
#
+auto_master # Use directory service
| #!/bin/bash | |
| # Dashing service | |
| # Add this file to /etc/init.d/ | |
| # $ sudo cp dashboard /etc/init.d/ | |
| # Update variables DASHING_DIR, GEM_HOME, & PATH to suit your installation | |
| # $ sudo nano /etc/init.d/dashboard | |
| # Make executable | |
| # $ sudo chmod 755 /etc/init.d/dashboard | |
| # Update rc.d | |
| # $ sudo update-rc.d dashboard defaults |