/System/Library/LaunchDaemons/com.apple.servermgrd.plist Is Missing - Causing postgres to not start properly
"Invalid or missing service identifier"  seems to mean that your plist file has not got or has  misspelled a section like

&lt;key&gt;Label&lt;/key&gt;
&lt;string&gt;com.foo.bar&lt;/string&gt;


Note "Label" must start with upper case L.