Buyer Beware: A Major Change in NFS (in Rawhide) is about to happen
James Laska
jlaska at redhat.com
Tue Oct 27 14:00:48 UTC 2009
On Mon, 2009-10-26 at 10:34 -0400, Steve Dickson wrote:
> [With the next nfs-utils rawhide build, I will be flipping the ]
> [switch that will cause all NFS client mounts to try NFS v4 first ]
> [At the bottom of this email has the workarounds if this change does ]
> [indeed cause pain ]
>
> As part of the https://fedoraproject.org/wiki/Features/NFSv4Default feature
> I am one commit away from changing the default protocol version NFS will
> be using (or at least trying to use).
>
> What does this means to you? Hopefully nothing! In theory this should
> be a very seamless transition but with all new technology there
> will be (and are) some rough spots.
>
> Why are make the change? See the NFSv4Default wiki for details,
> but in a nutshell:
> * Better performance - V4 is now a stateful protocol. Meaning the server keeps
> state on all the clients access a particular file or directory. This
> allows the server to give out delegations (or leases) which in turn
> allows the client to aggressive cache both data and meta data locally
>
> * Firewall Friendly- With v4 only one port is used 2049 for all traffic
> including mounting and file locking.
>
> * Finally it enables us use upcoming minor releases of the the protocol.
> NFS version 4.1 and pNFS are two example of upcoming minor releases.
>
>
> FYI, V4 was introduced in Fedora Core 2 so it has been around for a while. I
> personally have been using it for my home directory for a couple years now..
> For more of the nitty gritty details see
> http://www.iaps.com/NFSv4-new-features.html
>
> That's the good news... Here is the bad....
>
> Because the mount command will try NFS v4 first, mounts to older Linux servers
> will start failing like:
>
> # mount linux-server:/export /mnt
> mount.nfs: mounting linux-server:/export failed, reason given by server:
> No such file or directory
>
> This is due to a defect in the Linux server exporting code, which is fixed
> in F-12, *but* there are a number of workarounds
>
> On the server (Which is suggested):
> * Add the following entry to the /etc/exports file:
> / *(ro,fsid=0) Note: 'fsid=0' is explained in the exports(5) man pages.
>
> On the client, go back to v3 mounts by doing one of the following:
>
> * Add -o v3 to command line, similar to:
> mount linux-server:/export /mnt
>
> * Change the default mount version in the new /etc/nfsmount.conf file by
> uncommenting the Nfsvers=3 setting in the 'NFSMount_Global_Options' section.
> See nfsmount.conf(5) man page for details. The diff would look like:
>
> --- /etc/nfsmount.conf.orig 2009-10-26 09:30:21.000000000 -0400
> +++ /etc/nfsmount.conf 2009-10-26 10:31:30.227443686 -0400
> @@ -31,7 +31,7 @@
> # Protocol Version [2,3,4]
> # This defines the default protocol version which will
> # be used to start the negotiation with the server.
> -# Defaultvers=4
> +Defaultvers=3
> #
> # Setting this option makes it mandatory the server supports the
> # given version. The mount will fail if the given version is
Haven't gone through the full thread yet, but is it worth adding a
note/admonition to our NFS installation instructions that changing the
nfs server configuration may be necessary?
http://docs.fedoraproject.org/install-guide/f12/en-US/html/ch03s05s02.html
Thanks,
James
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