FedFsNfsServer0.8

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== Introduction ==
== Introduction ==
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This article describes how to configure a Linux NFS server to resolve junctions.  Once a file server can resolve junctions in its local file systems, it can participate in a FedFS domain.
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A [[FedFsGlossary#Junction|junction]] is a link between two shared file systems
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A ''[[FedFsGlossary#Junction|junction]]'' is a link between two shared file systems.  These shared file systems might not reside on the same server.
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A junction stores a list of [[FedFsGlossary#Location|locations]]. When a client attempts to access a junction, a file server must convert this list into a [[FedFsGlossary#Referral|referral]]This is known as [[FedFsGlossary#Junction_Resolution|junction resolution]].
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There may be more than one replica of the linked-to shared file system, stored on several different file servers.  Each replica of the linked-to file system is called a ''[[FedFsGlossary#Location|location]]''.
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A junction stores a list of locations.  A file server must convert this into a format which is correct for the protocol clients are using to access the server (say, NFSv4)The server-side process of recognizing a junction and converting its contents is known as ''[[FedFsGlossary#Junction_Resolution|junction resolution]]''.
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On Linux, a junction is denoted by a directory with special mode bits and an extended attribute that contains the junction location list.  The NFS server must convert a junction's location information into an NFSv4 referral which can be sent to NFS clients.
On Linux, a junction is denoted by a directory with special mode bits and an extended attribute that contains the junction location list.  The NFS server must convert a junction's location information into an NFSv4 referral which can be sent to NFS clients.
When the Linux in-kernel NFS server encounters a junction, it resolves the junction by performing an upcall to mountd.  It is mountd that actually reads a junction and converts it to information that the kernel NFS server can put on the wire as an NFSv4 referral.
When the Linux in-kernel NFS server encounters a junction, it resolves the junction by performing an upcall to mountd.  It is mountd that actually reads a junction and converts it to information that the kernel NFS server can put on the wire as an NFSv4 referral.
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This article describes how to configure a Linux NFS server to resolve junctions.  Once a file server can resolve junctions in its local file systems, it can participate in a FedFS domain.
== Build nfs-utils ==
== Build nfs-utils ==

Revision as of 16:29, 27 November 2012

Project: fedfs-utils

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Introduction

A junction is a link between two shared file systems

A junction stores a list of locations. When a client attempts to access a junction, a file server must convert this list into a referral. This is known as junction resolution.

On Linux, a junction is denoted by a directory with special mode bits and an extended attribute that contains the junction location list. The NFS server must convert a junction's location information into an NFSv4 referral which can be sent to NFS clients.

When the Linux in-kernel NFS server encounters a junction, it resolves the junction by performing an upcall to mountd. It is mountd that actually reads a junction and converts it to information that the kernel NFS server can put on the wire as an NFSv4 referral.

This article describes how to configure a Linux NFS server to resolve junctions. Once a file server can resolve junctions in its local file systems, it can participate in a FedFS domain.

Build nfs-utils

On Fedora 18, rpc.mountd already has working junction resolution support. On other distributions, you'll need to build a version of rpc.mountd with working junction resolution support.

First, you'll need to install the nfs-plugin.h header.

The "make install" step should install the header in /usr/include/nfs-plugin.h . If not, you can find it in fedfs-utils-0.8/src/include/nfs-plugin.h and install it by hand.

Now download and unpack the latest nfs-utils tarball on the same system where you built fedfs-utils. Build nfs-utils, and replace rpc.mountd on your NFS server. The configure options are complicated; I usually copy them from the latest nfs-utils RPM spec file from my distribution.

$ ./configure yada yada
$ make
$ sudo install utils/mountd/mountd /usr/sbin/rpc.mountd

Then restart the NFS service.

# systemctl restart nfs-server.service
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