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From: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
To: Jim Rees <rees@umich.edu>
CC: James <purpleidea@gmail.com>, Chuck Lever <chuck.lever@oracle.com>,
        "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: RE: NFS clientaddr, kerberos
Date: Mon, 24 Jun 2013 13:37:17 +0000
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> -----Original Message-----
> From: linux-nfs-owner@vger.kernel.org [mailto:linux-nfs-
> owner@vger.kernel.org] On Behalf Of Jim Rees
> Sent: Sunday, June 23, 2013 3:43 PM
> To: Myklebust, Trond
> Cc: James; Chuck Lever; linux-nfs@vger.kernel.org
> Subject: Re: NFS clientaddr, kerberos
> 
> Myklebust, Trond wrote:
> 
>   > > 	echo "options nfs callback_tcpport=<port>"
> >>/etc/modprobe.d/options-local.conf
>   > This is very useful to know.
>   > Is there any way to specify this as a mount option?
> 
>   No. The NFSv4 callback channel port number is a global property. It does
>   not want to be a per-mount thing.
> 
> Would it make sense as a sysctl? I can sort of imagine cases where this might
> be useful. Not that I'm volunteering to implement it.

Hi Jim,

With the sysfs interface to kernel parameters, there is little advantage in implementing a sysctl.
Since this is a writeable kernel parameter, it means that you can also change it via the pseudofile in /sys/module/nfs/parameters/callback_tcpport after the module has been loaded (but you still need to do so before mounting any NFSv4 volumes).

Cheers
  Trond