Documenting Cygwin on NFS, no longer only exchange-medium! Re: How to fix |mkfifo()| failure if |pathname| is on NFS ? / was: Re: [EXTERNAL] Re: mkfifo: cannot set permissions of 'x.fifo': Not a directory

[Corinna Vinschen]

On Aug 26 19:44, Martin Wege via Cygwin wrote:
> On Fri, Aug 25, 2023 at 2:19 PM Corinna Vinschen via Cygwin
> <cygwin@cygwin.com> wrote:
> >
> > On Aug 23 01:05, Roland Mainz via Cygwin wrote:
> > > Note that Cygwin does not interpret the file |myfifo.fifo| as FIFO,
> > > instead it comes back as a symlink "myfifo.fifo -> ':\0:c4:1000'".
> > >
> > > AFAIK there are (at least) these two options to fix the problems:
> > > 1. Check whether the filesystem for the fifos path is NFS
> > > (cgywin.dll's |fs.fs_is_nfs()|), and if it is a symlink check if it
> > > starts with ':\0:c4:' (assuming "c4" is the prefix for inodes created
> > > with |mkfifo()|). If this condition is |true|, then cygwin |stat()|,
> > > |open()| etc. should treat this inode as FIFO.
> >
> > The downside is that it is not possible to diffentiate between Cygwin
> > FIFOs and real FIFOs created from the remote side in `ls -l'
> > output.  Note that Cygwin returns the NFS stat info verbatim, so
> > a real FIFO is returned as a real FIFO:
> >
> >   linux$ mkfifo bar
> >   cygwin$ ls -l bar
> >   prw-r--r-- 1 corinna vinschen  0 Aug 25 13:58 bar
> >
> > The idea was always to use NFS as exchange medium, but not as
> > installation medium for the entire distro or to keep Cygwin home
> > dirs on NFS.  There were times where NFS was pretty unstable.
> > I used NFS for quite some time to build Cygwin packages, but at one
> > point I got trouble (performance problems with multiple concurrent
> > processes accessing an NFS share, build errors out of the blue),
> > so I switched to Samba shares, albeit grudgingly.  I'm not yet
> > sure if the problems are fixed.  At least a recent OpenSSH build
> > ran through without problems...
> 
> Corinna, could you please update the Cygwin documentation then? We use
> NFS, both Windows builtin and CITI NFSv4.1, with Cygwin for years
> without major problems, so that comment about exchange-medium-only is
> clearly wrong!

I'm talking about the idea how users would use NFS, and the idea was
that nobody in their right mind would use a crippled filesystem (from
the Windows POV) for the entire installation.  Before you came up with
your complaints, nobody here even knew that somebody actually did that.

NFS is a niche filesystem on Windows and was never in the focus of
anybody here, except me, because I was toying around with it and was
happy to have it working.  As far as I knew until a few days ago,
I was the only user of Cygwin's NFS support.

As for FIFOs on NFS, as I wrote, they never worked as desired on NFS.
For kicks I tried back until Cygwin 3.3.  Given this isn't a regression,
it won't be fixed for Cygwin 3.4.

As Brian wrote in his reply to your mail, we are all volunteers here.
Everybody working on Cygwin is working in their spare time and/or on the
goodwill of their employer.

Cygwin is open source.  You can fix or implement stuff yourself and send
the patches to the cygwin-patches ML for review.  Otherwise you will
have to let us, the people actually working on the project, decide when
and how something gets implemented.

Having said that, I have a local patch enabling FIFOs on NFS.  I might
push it at one point to the main branch, but the pressure you guys are
currently building up on this mailing list puts me right off.


Corinna