Re: Questions and problems with NFS4

From: J. Bruce Fields
Date: Fri Jul 30 2010 - 14:49:00 EST

On Fri, Jul 30, 2010 at 02:18:37AM +0200, J.A. MagallÃn wrote:
> First of all, plz correct me if this is in some kind of wiki, web page or
> the like, but I have not been able to find it. All this things should be
> on a document somewhere, perhaps even in the kernel itself...


> These are the things I have found out (thanks to your answers...).
> I'm a long time unix admin, not new to NFS, but all this things were not
> obvious to me, so perhaps they deserve to be in a document, something like
> "NFS 3 to 4 migration for dummy admins":
> - Everything just works if you mount shares as nfs4. Even, if you have a
> bunch of linux boxen with recent kernel/nfs-utils, probably you are
> already doing nfs4... modern mount tries nfs4 first.
> - Using nfsroot with fsid=0 is not mandatory, nor bind-mounting everything
> under some /export (like many documents say), that only forces you to

We should update that documentation.

> use the old way of specifying paths in the server (absolute, not
> relative to /export).
> - Even if you use nfsroot(fsid=0), and you mount it on the client
> at /somepoint, you are not forced to mount everything else under
> /somepoint (plz, correct me if I'm wrong).
> - You can strip your server for NFS4, but not too much... Old daemons
> are still needed locally. For example, you can get rid of NFS2 and
> UDP for nfsd (-N 2 -U, -any os still uses NFS2??-), and old
> mount protocols (-N 1 -N 2 for mountd)...
> - ... but they can be firewalled, use is just local
> - portmap/rpcbind is not needed, but still used because nfsd is not
> yet proper clean for only-nfs4-behavior.
> There are also some things I have not been able to discover, like
> using the interesting things of NFS4:
> - How do you activate delegations ? Is this an automatic thing, or
> do I have to add any option somewhere ?

It's automatic. You can turn them off on the server side with
/proc/sys/fs/leases-enable. They'll be turned off automatically if the
server can't open a tcp connection back to the client (for example, if
the client is behind a NAT).

> - How do you use cache ? Many docs talk about fsc option, but man
> does not mention it (nfs-utils 1.2.2).
> I have tried to use cachefiles module, and cachefilesd, but
> when I try to run it, I get:

I haven't used that. I don't believe there's anything NFSv4-specific
about it.

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