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From: Cedric Blancher <cedric.blancher@gmail.com>
Date: Wed, 22 Nov 2023 23:41:29 +0100
Message-ID: <CALXu0Ufx4muT4vpLBcBW5cunODzTWo=940NKAD5GoS05jHZhAQ@mail.gmail.com>
Subject: Re: How to set the NFSv4 "HIDDEN" attribute on Linux?
To: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
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On Mon, 20 Nov 2023 at 15:44, Chuck Lever III <chuck.lever@oracle.com> wrot=
e:
>
>
>
> > On Nov 20, 2023, at 6:46=E2=80=AFAM, Jeff Layton <jlayton@kernel.org> w=
rote:
> >
> > On Sun, 2023-11-19 at 17:51 +0100, Cedric Blancher wrote:
> >> On Sat, 18 Nov 2023 at 12:56, Jeff Layton <jlayton@kernel.org> wrote:
> >>>
> >>> On Sat, 2023-11-18 at 07:24 +0100, Cedric Blancher wrote:
> >>>> Good morning!
> >>>>
> >>>> NFSv4 has a "hidden" filesystem object attribute. How can I set that
> >>>> on a Linux NFSv4 server, or in a filesystem exported on Linux via
> >>>> NFSv4, so that the NFSv4 client gets this attribute for a file?
> >>>>
> >>>
> >>> You can't. RFC 8881 defines that as "TRUE, if the file is considered
> >>> hidden with respect to the Windows API." There is no analogous Linux
> >>> inode attribute.
> >>
> >> Can we use setfattr and getfattr to set/get the NFSv4.1 HIDDEN and
> >> ARCHIVE? We have Windows NFSv4 clients (and kofemann/Roland's codebase
> >> supports this), and that means we need to be able to set/get and
> >> backup/restore these flags on the NFSv4 server side.
> >>
> >
> > No. They would need to be stored in the inode on the server somehow and
> > there is no place to store them. These attributes are simply not
> > supported by the Linux NFS server.
>
> To be clear: these attributes are not supported within the Linux
> filesystems themselves. NFSD could of course handle these attributes,
> but there is simply no mechanism to make them persistent on Linux
> filesystems.

You have the setfattr/getfattr attributes on Linux, which can easily
store such boolean flags.

It would also solve the backup and restore issue, as GNU tar supports
these via tar --xattrs

>
> NTFS might be an exception to that, but I believe Linux does not
> allow mounted NTFS filesystems to be modified. So again, no way
> to make those attributes persistent.

New NTFS kernel driver in Linux 6.x supports r/w operation

>
> But I do wonder how Samba on Linux handles these guys. NFSD should
> do something that doesn't conflict with that.

Did anyone figure that one out?

Ced
--=20
Cedric Blancher <cedric.blancher@gmail.com>
[https://plus.google.com/u/0/+CedricBlancher/]
Institute Pasteur