Can't write to FIFO file mouted via NFS

Question

I'm trying to write to FIFO file locate on NFS mount and it blocks. What could be the problem?

My /etc/export:

/tmp/test/ 10.0.0.0/24(rw,no_root_squash,async)

ls /tmp/test on NFS server and client is the same

prw--w--w- 1 root root 0 2009-06-24 17:28 ui-input

and I'm writing as root

Thanks.

Answer 1

This response is probably too late to help you now, but it's notable that you could achieve a similar effect using named pipes and the "nc" (netcat) command. Netcat can accept input from standard input (or a named pipe) and echo it out over a socket to another instance of netcat on another host, optionally to a named pipe.

So basically, your setup would look like this:

Host1$ mkfifo Host1_named_pipe
Host1$ nc -l 1234 > Host1_named_pipe

Host2$ mkfifo Host2_named_pipe
Host2$ nc Host1 1234 < Host2_named_pipe

Now, when you run a program on Host2 and send its output to Host2_named_pipe, that output will come out of Host1_named_pipe on Host1.

or via ssh :

Host1$ mknode Host1_named_pipe p
Host2$ mknode Host2_named_pipe p

Host1$ cat Host1_named_pipe | ssh Host2 'cat - > Host2_named_pipe'

Answer 2

A FIFO is meant to be an inter-process communication mechanism. By trying to export the FIFO via NFS, you are asking the kernel to treat the local inter-process communication as more of a network communication mechanism.

There are a number of issues associated with that, the most obvious one being that the FIFO read implementation inside the kernel expects a buffer in userspace to copy the data to. Such a buffer is not directly available in NFS. Thus, the Kernel does not support the export of FIFOs over NFS.

You may want to use sockets for network communication instead.