Configuring the NFS Server on the Command Line

To configure a Red Hat Enterprise Linux system as an NFS server via the command line, make sure the nfs-utils RPM package is installed.

The server configuration file, /etc/exports, uses the following format:

shared_directory allowed_hosts(options)

where shared_directory is the name of the directory to be shared, allowed_hosts is the IP address range of the allowed clients, and options is a list of NFS options for the exported directory. Obviously, the exported directory must exist. You must be root to modify this file.

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NFS and SELinux Configuration

NFS and SELinux

In Red Hat Enterprise Linux 5 & 6, NFS is protected by the default Security-Enhanced Linux (SELinux) policy, known as the targeted policy. By default, this targeted policy allows NFS connections to the server by setting the nfs_export_all_ro and nfs_export_all_rw SELinux booleans to 1.

If you are sharing home directories over NFS while using SELinux, you must set

use_nfs_home_dirs boolean to 1 on each client connecting to the NFS server sharing the home directories. Execute the following command as root:

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What is NFS server

Network File Sharing

In an enterprise computing environment, it is common to share files between computers or allow several users to access the same set of files on a central server and have all changes be visible to all users immediately. In a pure UNIX environment, including those consisting solely of Red Hat Enterprise Linux systems, this can be achieved via Network File System (NFS). If sharing files between Red Hat Enterprise Linux and Microsoft Windows systems is desired, Samba can be used to achieve connectivity.

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Understanding PAM, or Pluggable Authentication Modules

PAM, or Pluggable Authentication Modules, is an authentication layer that allows programs to be written independent of a specific authentication scheme. Applications request authentication via the PAM library, and the PAM library determines whether the user is allowed to proceed. If an administrator wants to implement a different authentication scheme, he just changes the PAM configuration files and the existing programs work seamlessly.

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Automation with crontab

Automation with crontab

In any operating system, it is possible to create jobs that you want to reoccur. This

process, known as job scheduling, is usually done based on user-defined jobs. For

Red Hat, this process is handled by the cron service, which can be used to schedule tasks (also called jobs). By default, Red Hat comes with a set of predefined jobs that occur on the system (hourly, daily, weekly, monthly, and with arbitrary periodicity). As an administrator, however, you can define your own jobs and allow your users to create them as well.

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Scheduling Tasks with Cron job

Now that you understand the basics of automating tasks with a script or program, the next step is to know how to schedule the tasks so they are executed at a specific time or on a set schedule. Some scripts such as removing users may not need to be scheduled, but others such as performing backups might work better on a schedule so users can anticipate them or so they can be run during a time when they won’t interfere with the daily workload of the system.

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Executing Commands in a Bash Script

To execute a series of commands in a Bash script, list each command on a separate line. For example, Listing shows the very basic Bash script that gathers information about system resources.

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