[Samba] os level permissions for samba 4 share

[Eduardo Sotomayor]

I read at the samba4 wiki that to setup a samba4 share you need to

 Create a folder that you want to share

# mkdir -p /srv/samba/Demo/

 Add a new share to your smb.conf:

[Demo]
     path = /srv/samba/Demo/
     read only = no


but what about permission at os level? I mean do I have to chmod 770
or chmod 2770 the folder or else?
I read somewhere that it was necessary to chmod 777 but that configuration is very unsecure at os level.

thanks