Encontrei minha solução em man exports
no mac:
-maproot=user:group1:group2:... The colon separated list is used to specify the precise credential to be used for remote access by root. The elements of the list may be either names or numbers. Note that ''user:'' should be used to distinguish a credential containing no groups from a complete credential for that user.
que leva a:
In the absence of -maproot and -mapall options, remote accesses by root will result in using a credential of -2:-2. All other users will be mapped to their remote credential. If a -maproot option is given, remote access by root will be mapped to that credential instead of -2:-2. If a -mapall option is given, all users (including root) will be mapped to that credential in place of their own.
Então eu usei:
/Users/garyrichardson/leap/nfs -rw -maproot=501:501 172.16.180.130