AMD-Action:authenticate:SP error while trying to download Xcode 7.1

That worked for me! Thanks.

Via command line (make sure Shared doesn't already exist on your primary drive and then run...):

$ cd /Volumes/PRIMARY/Users

$ sudo mkdir Shared

$ sudo ditto /Volumes/SECONDARY/Users/Shared /Volumes/PRIMARY/Users/Shared/

http://osxdaily.com/2014/06/11/use-ditto-copy-files-directories-mac-command-line /

This is alternate solution if your comfortable with the command line and using a terminal.

I had relocated the Shared directory and was using a symbolic link from /Users/Shared -> To my second disk location, then I upgrade and bang started getting the error. I figured the problem out but was not satisfied with answer and though I could work around it I wanted something better.

I had a space issue's as I use music software, the samples want to install under /Users/Shared. So being available for every user with an account. I did not have the luxury of space on the primary drive. But I have to say that apple not respecting a symbolic link is pretty stupid, that's why they where invited to help relocate resource and abstract away and make transparent any dependencies.

Regardless I found an alternate solution , the apple version of the mount command has less functionality than the version found on Linux. On Linux you can use the mount command with a --bind option to mount a directory from one location to another directory.

So this solution makes use of bindfs a tool design fro the job.

1. Install FUSE for OS X
2. Install Brew or update your existing install via

   brew update

3. In a Terminal:

   brew install bindfs

4. sudo mkdir /Users/Shared
5. sudo bindfs -o volname="Shared" /Volumes/MySecondDisk/Shared/ /Users/Shared

This presents a volume at the correct system level, its a simple matter of putting this in script and associating with your start-up items eg.

#!/bin/bash

sudo /opt/local/bin/bindfs -o volname="Shared" /Volumes/USB1/Shared/ /Users/Shared