Automounting Volumes on OS XRevisionas of Monday, 21 December 2015 at 02:30 UTC

OS X (client) will only mount external drives on user login (and not
reboot). To correct this,

 sudo defaults write /Library/Preferences/SystemConfiguration/autodiskmount AutomountDisksWithoutUserLogin -bool true

This creates a file:

 /Library/Preferences/SystemConfiguration/autodiskmount.plist