[Samba] create mask, create vs copy file

[Andy Smith]

Hi, 

  I have an issue whereby when I create a new file it obeys the create
mask defined for the share but when I copy a file from within the same
directory the file is created without write permssions for the primary
group. 

Ie: directory has permissions 770, existing file has permissions of 770,
create mask is 0770. When I copy a file its permissions are 750. However
when creating a new file permissions are correctly set to 770. I'm a bit
stumped really, surely create mask should work regardless of whether I'm
copying or creating files? Or is the windows client somehow trying to
read the permssions of the existing file and is doing a bad job of
copying the permissions to the new file? 

the environment is Ubuntu 14 LTS and samba 4.3 

thanks, Andy.