Re: NFSv4.x export options to mark export as case-insensitive, case-preserving? Re: LInux NFSv4.1 client and server- case insensitive filesystems supported?

Chuck Lever
2025-09-09T19:32:57Z

On 9/9/25 12:33 PM, Cedric Blancher wrote:
> On Tue, 9 Sept 2025 at 18:12, Chuck Lever <chuck.lever@oracle.com> wrote:
>>
>> On 9/9/25 12:06 PM, Cedric Blancher wrote:
>>> Due lack of a VFS interface and the urgend use case of needing to
>>> export a case-insensitive filesystem via NFSv4.x, could we please get
>>> two /etc/exports options, one setting the case-insensitive boolean
>>> (true, false, get-default-from-fs) and one for case-preserving (true,
>>> false, get-default-from-fs)?
>>>
>>> So far LInux nfsd does the WRONG thing here, and exports even
>>> case-insensitive filesystems as case-sensitive. The Windows NFSv4.1
>>> server does it correctly.

As always, I encourage you to, first, prototype in NFSD the hard-coding
of these settings as returned to NFS clients to see if that does what
you really need with Linux-native file systems.

>> Hi Cedric,
>>
>> Can you send a pointer to some documentation for the Windows NFSv4.1
>> implementation of this feature?
>
> That is just ON by default for the Windows NFSv4.1 server if you
> export NTFS, and OFF by default for DVDs.
> We never had to change it.
>
> https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/nfsadmin
> explains a bit of it, but for Windows Server 2022 and 2025 it's a bit
> different. Part of the more interesting docs are behind a
> paywall/Microsoft login.

The feature is comprised of these three configuration options:

translationfile=<file> - Specifies a file containing mapping information
for replacing characters in the names of files when moving them from
Windows-based to UNIX-based file systems. If file is not specified, then
file name character translation is disabled. If the value of
translationfile is changed, you must restart the server for the change
to take effect.

casesensitivelookups={yes|no} - Specifies whether directory lookups are
case sensitive (require exact matching of character case).
You must also disable Windows kernel case-insensitivity to support
case-sensitive file names. To support case-sensitivity, change the DWord
value of the registry key, HKLM\SYSTEM\CurrentControlSet\Control\Session
Manager\kernel, to 0.

ntfscase={lower|upper|preserve} - Specifies whether the case of
characters in the names of files in the NTFS file system will be
returned in lowercase, uppercase, or in the form stored in the
directory. The default setting is preserve. This setting can't be
changed if casesensitivelookups is set to yes.

Sounds like there is more going on than just setting an export option. I
will need to hunt down a Microsoft NFS developer to find out how much
the shared file system is involved in handling internal filename
resolution. I'm at SDC next week, there should be one or two there.

--
Chuck Lever