Who's 4294967294? 

Why is /mnt/nfs owned by something like 4294967294 and why is the group set to the same? Why there are no permissions for anyone except the owner on the nfs directory?  I am root on the Linux client so why is myfile owned (again) by 4294967294?

Well, first of all, remember we have not configured User Name Mapping so the Windows system has no idea about who you are so every NFS communication going from this host to the server is treated as anonymous access by the Windows system. The UID used for such communication is 4294967294 for operating systems that understand 64-bit calculations and 65535 for 32-bit capable operating systems. And that’s the reason you see 4294967294 owning the NFS mount point and the newly created myfile1.

So since Windows system doesn’t have mapping information for you, it treats  your access as anonymous access and assumes you’re a user with UID/GID of -2 and this is resolved to 4294967294 on Windows systems.

This same UID and GID is also used for all accesses from NFS clients where Windows server cannot determine the mapping information. This is slightly different than the all_squash option on Linux systems where all access requests are treated as anonymous access irrespective of whether or not there’s a corresponding entry in the /etc/passwd or /etc/group files (or NIS maps).

So now it’s easy to answer those questions – The nfsshare folder on the Windows server is owned by Administrators group. This is not yet mapped to any group using User Name Mapping so it is translated to -2 (and in turn to 4294967294).

In NTFS file system, although, an object has an owner AND a primary group, this primary group is not used by the Win32 subsystem and almost none of the windows based program can set it for you but it can be used and set by applications which can use the POSIX semantics implemented in NTFS file system. Here's more about it.

We have used Explorer to create this folder therefore the primary group for this folder is set to None or NULL SID and in the UNIX-style listing that gets to displayed as 4294967294.

If you want to set this primary group information, you can use chown.exe and chgrp.exe commands shipped with Interix or SUA. And, if you want to manage the permission the UNIX way, chmod.exe is there too.

You’re root (UID/GID) on the Linux system and since the root squashing is ON (remember that Allow root access check-box?), root is assumed as anonymous and that makes myfile1 created as 4294967294/4294967294. This also true if you’ve mapped the root user to a valid Windows user but have not turned on the Allow root access check-box.

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