FedFsNfsAutomounter0.9

From Linux NFS

Revision as of 15:43, 17 October 2012

Project: fedfs-utils

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Introduction

One goal of FedFS is to present applications with the same file namespace no matter what client instance they are running on. These consistent FedFS pathnames are called Globally Useful Names.

A Globally Useful Name begins with a top level directory named after the file-access protocol. For NFS, that's /nfs4. Subdirectories of this directory are named after FedFS domains. They are mounted when someone on the client changes into a directory named after a corresponding FedFS domain.

Under /nfs4, you might see, for example, a corporate.example.com directory, a sales.example.com directory, and an engineering.example.com directory. Each of these directories contains the directories and data in its respective FedFS domain.

On Linux, autofs is used to create the top level of the space of Global Usefuls. Once the domain root directory of a FedFS domain is mounted, the Linux NFS client mounts the lower parts of each domain's namespace.

At this time, there is no way to allow an "ls" in /nfs4 to show possible FedFS domains. Autofs will unmount and remove idle directories in the /nfs4 directory automatically. Users and applications have to know the names of interesting FedFS domains in order to start populating the FedFS namespace on their clients.

Installing autofs

Most recent distributions have a pre-built version of autofs installed by default. If you see the file /etc/auto.master on your clients, then autofs is already installed. If it is not yet installed, consult your distribution's system administration documentation for the steps needed to install and configure autofs.

Installing the FedFS program map

A program map is used to convert a FedFS domain name to the correct NFS server to mount under /nfs4. On Fedora 17 or later, a pre-packaged version of the program map executable can be installed with:

 # yum install fedfs-utils-client

The executable is installed in /usr/sbin/fedfs-map-nfs4 .

If your distribution does not provide a pre-packaged version of fedfs-utils, you can build it from scratch. After downloading the tarball, the usual "./configure; make" ritual will suffice. The program map is in src/mount/fedfs-map-nfs4. Use the install program to install it:

 # install src/mount/fedfs-map-nfs4 /usr/sbin

The program map employs the /sbin/mount.nfs program to populate the /nfs4 directory. Ensure that your client has /sbin/mount.nfs installed.

Final steps

Now that you have autofs working and the FedFS program map installed on your client, create the top level directory for the FedFS namespace:

 # mkdir /nfs4

Add the program map to /etc/auto.master by introducing this line:

 /nfs4    /usr/sbin/fedfs-map-nfs4

Restarting the autofs daemon or rebooting your client should be enough to complete the configuration.