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Date:   Fri, 6 Nov 2020 16:46:40 -0500
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Vasyl Vavrychuk <vvavrychuk@gmail.com>
Cc:     Patrick Goetz <pgoetz@math.utexas.edu>, linux-nfs@vger.kernel.org
Subject: Re: Hard linking symlink does not work
Message-ID: <20201106214640.GC26028@fieldses.org>
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On Wed, Oct 28, 2020 at 10:53:20AM +0200, Vasyl Vavrychuk wrote:
> Thanks for replies about my problem. It is actually a practical one...
> 
> I need to compile Yocto BSP which builds only under older
> distributions. For convenience I have established a Vagrant virtual
> machine which uses NFS to share workspace with the host machine.
> 
> Now coming back to hardlinking symlinks.
> 
> Yocto build system uses hardlinks to prepare sysroot for packages, and
> symlinks are part of that sysroot provided by other packages.

For what it's worth, I can't reproduce the problem, linking a symlink
works fine for me.

What's your server?  (OS, version, exported filesystem?)

--b.

> 
> On Tue, Oct 27, 2020 at 10:03 PM Patrick Goetz <pgoetz@math.utexas.edu> wrote:
> >
> >
> >
> > On 10/27/20 12:12 PM, J. Bruce Fields wrote:
> > > On Fri, Oct 23, 2020 at 01:13:02PM +0300, Vasyl Vavrychuk wrote:
> > >> I have found that hard links for regular files works well for me over NFS:
> > >>
> > >> $ touch bar
> > >> $ ln bar tata
> > >>
> > >> But if I try to make hard link for symlink, then it fails:
> > >>
> > >> $ ln -s foo bar
> > >> $ ln bar tata
> > >> ln: failed to create hard link 'tata' => 'bar': Operation not permitted
> > >
> > > Huh.  I'm not sure I even realized it was possible to hardlink symlinks.
> > > Makes sense, I guess.
> >
> > What's even the use case for hard linking a symlink?  That sounds like
> > asking for trouble...
> >
> >
> > >
> > > I think my first step debugging this would be to watch wireshark while
> > > attempting the "ln", and see what happens.  That should tell us whether
> > > it's the client or server that's failing the operation.
> > >
> > > --b.
> > >
> > >>
> > >> I am using NFSv4 with Vagrant, here is mount entry:
> > >>
> > >> 172.28.128.1:PATH on /vagrant type nfs4
> > >> (rw,relatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=IP,local_lock=none,addr=IP)
> > >>
> > >> I have also verified that rpc-statd is running on host.
> > >>
> > >> Host machine is Ubuntu 18.04 with NFS packages version 1:1.3.4-2.1ubuntu5.3.
> > >>
> > >> Will appreciate help on this.
> > >>
> > >> Thanks,
> > >> Vasyl