FedFsNfsServer0.8
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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]]''. | 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 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]]''. | 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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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. | ||
Revision as of 19:39, 24 October 2012
Project: fedfs-utils
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Introduction
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.
A 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 location.
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 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.
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
