[Samba] [samba] file server: %U or %u?

[mathias dufresne]

Hi all,

Here there are trust relationship between domains.
On some file server using Samba 4.4.4 (Centos 7) I must set up my shares
using %U. When using %u the directory which is accessed is
/path/to/share/OUR_DOMAIN\username rather than /path/to/share/username.

Initially I thought it could be solved by using:
  winbind use default domain = yes
associated with:
  workgroup = OUR_DOMAIN
but that change only how users are generated by Winbind (or at least that's
how I feel it :)

And as smb.conf manpage tells:
 %U
           session username (the username that the client wanted, not
necessarily the same as the one they got).

I feel like it could be nice (because perhaps more secure) to use %u...