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

Martin Wege
Sat Aug 26 17:44:21 GMT 2023

On Fri, Aug 25, 2023 at 2:19 PM Corinna Vinschen via Cygwin
<> 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!


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