NFS (NETWORK FILE SYSTEM)

The NFS service enables computers of different architectures that run different operating systems to share file systems across a network. NFS support has been implemented on many platforms that range from the MSDOS to the VMS operating systems.The NFS environment can be implemented on different operating systems because NFS defines an abstract model of a file system, rather than an architectural specification. Each operating system applies the NFS model to its filesystem semantics. This model means that file system operations such as reading and writing function as though the operations are accessing a local file.

The NFS service has the following benefits:

● Enables multiple computers to use the same files so that everyone on the network can access the
    same data
● Reduces storage costs by having computers share applications instead of needing local disk space
    for each user application
● Provides data consistency and reliability because all users can read the same set of files
● Makes mounting of file systems transparent to users
● Makes accessing of remote files transparent to users
● Supports heterogeneous environments
● Reduces system administration overhead

The NFS service makes the physical location of the file system irrelevant to the user. You can use the NFS implementation to enable users to see all the relevant files regardless of location. Instead of placing copies of commonly used files on every system, the NFS service enables you to share the original file from the NFS server's file system. All other systems access the files across the network. Under NFS operation, remote file systems are almost indistinguishable from local file systems.

The NFS service provides support for mirror mounts. Mirror mounts enable an NFSv4 client to traverse shared file system mount points in the server namespace. For NFSv4 mounts, the automounter will perform a mount of the server namespace root and rely on mirror mounts to access its file systems. The main advantage that mirror mounts offer over the traditional automounter is that mounting a file system using mirror mounts does not require the overhead associated with dministering automount maps.

=> how to do it step by step and how to use and validate?

To set up an NFS server:

1. Install the nfs-utils package.
   

   # yum install nfs-utils

2. Create the directory where you will copy the full Oracle Linux Release 6 Media Pack DVD image, for example /var/OSimage/OL6.6:
   

   # mkdir -p /var/OSimage/OL6.6

3. Edit the configuration file, /etc/exports, as follows.
   
   1. Add an entry for the directory where you will copy the DVD image.
      The following example allows read-only access to the directory /var/OSimage/OL6.6 for any NFS client on the 192.168.1 subnet:
      

      /var/OSimage/OL6.6 192.168.1.0/24(ro)

   2. Save your changes to the file.
4. Start the NFS server, and configure it to start after a reboot.
   

   # service rpcbind start
   # service nfs start
   # service nfslock start
   # chkconfig rpcbind on
   # chkconfig nfs on
   # chkconfig nfslock on

5. If you have configured a firewall on your system, configure it to allow incoming NFSv4 requests from NFS clients.
   For example, use the following commands to configure iptables to allow NFSv4 connections and save the change to the firewall configuration:
   

   # iptables -I INPUT -p tcp -m state --state NEW -m tcp --dport 2049 -j ACCEPT
   # service iptables save

 To configure an existing NFS server:

1. Create the directory where you will copy the full Oracle Linux Release 6 Media Pack DVD image, for example /var/OSimage/OL6.6:
   

   # mkdir -p /var/OSimage/OL6.6

2. Use the exportfs command to export the directory.
   

   # exportfs -i -o options client:export_dir

   
   For example, to allow read-only access to the directory /var/OSimage/OL6.6 for any NFS client on the 192.168.1 subnet:
   
   

   # exportfs -i -o ro 192.168.1.0/24:/var/OSimage/OL6.6