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.  Junctions tie together disparate filesystems to create a [[FedFsGlossary#FedFs_Domain|FedFS domain]].
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A ''[[FedFsGlossary#Junction|junction]]'' is a link between two shared file systems.  The two shared file systems may not reside on the same server.  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 [[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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Junctions store a list of locations.  Each location in the list is represented as an export path paired with a server name or IP address.  When a file-access client encounters a junction, the file server (via a ''[[FedFsGlossary#Referral|referral]]'') provides the stored list of locations to the client, who chooses a location and mounts it.
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A file server must convert the information stored in a junction into a list of locations that's in 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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A single junction is useful for linking together two shared file systems.  A web of junctions can be used to create a namespace that crosses between multiple file systems on multiple file servers.  FedFS uses junctions for just such a purpose.
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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.
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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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== Installing or Building fedfs-utils ==
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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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* [[FedFsUtilsBuild0.8|Installing or Building fedfs-utils-0.8]]
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=== Additional instructions ===
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Instead of installing the whole package, you may choose to install just the server components.  The plug-in library:
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# cd fedfs-utils-0.8/src/plug-ins ; make install
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The header describing the library's API is needed to enable junction support while building nfs-utils:
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== Build nfs-utils ==
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  # cd fedfs-utils-0.8/src/include ; make install
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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.
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And finally, the "nfsref" command:
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First, you'll need to install the nfs-plugin.h header.
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# cd fedfs-utils-0.8/src/nfsref ; make install
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* [[FedFsUtilsBuild0.8|Building fedfs-utils-0.8]]
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=== Build nfs-utils ===
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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.
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.

Latest revision as of 16:30, 27 November 2012

Project: fedfs-utils

[ Project Home | News | Downloads | Docs | Mailing Lists | Source Control | Issues ]

Introduction

A junction is a link between two shared file systems. Junctions tie together disparate filesystems to create a FedFS domain.

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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