I have an external hard drive connected to my Mac OSX ML box. I wanted to setup a web server to access files on it, but the permission on all files and directories on the drive are "rwx" for the owner which is my local admin, and the group is the "staff" group. I need the files readable by the apache user _www and group _www, I was trying to set all files to be sudo chown -R _www:_www /Volumes/raid_mirror/WebDAV, but this doesn't do anything (gives no errros, just has no effect.) I tried chaning the group using "chgrp" to _www, but that won't work either, it gives me no errors and user and group remain the same.
OS X ignores ownership on external drives by default (on the theory that they probably came from some other computer with completely different accounts). You can change this in Finder by getting info on the volume and deselecting "Ignore Ownership on this Volume" (see Apple support document #PH10670, but reverse the process), or in Terminal with