Chapter 12.

Network Scripts

Using Red Hat Linux, all network communications occur between configured interfaces and physical

networking devices connected to the system. The different types of interfaces that exist are as varied

as the physical devices they support.

The configuration files for network interfaces and the scripts to activate and deactivate them are located

in the

/etc/sysconfig/network scripts/

directory. While the existence of interface files can

differ from system to system, the three different types of files that exist in this directory, interface

configuration files, interface control scripts, and network function files, work together to enable Red

Hat Linux to use various network devices.

This chapter will explore the relationship between these files and how they are used.

12.1. Network Configuration Files

Before we review the interface configuration files themselves, let us itemize the primary configuration

files used by Red Hat Linux to configure networking. Understanding the role these files play in setting

up the network stack can be helpful when customizing your system.

The primary network configuration files are as follows:

  /etc/hosts

  The main purpose of this file is to resolve hostnames that cannot be resolved

any other way. It can also be used on resolve hostnames on small networks with no DNS serer.

Regardless of the type of network the computer is on, this file should contain a line specifying the IP

address of the loopback device (

127.0.0.1

) as

localhost.localdomain

. For more information

see the hosts man page.

  /etc/resolv.conf

  This file specifies the IP addresses of DNS servers and the search domain.

Unless configured to do otherwise, the network initialization scripts populate this file. For more

information on this file see the resolv.conf man page.

  /etc/sysconfig/network

  Specifies routing and host information for all network interfaces.

For more information on this file and what directives it accepts, see Section 3.7.1.23.

  /etc/sysconfig/network scripts/ifcfg  interface name

  For each network in 

V

W

terface on a Red Hat Linux system, there is a corresponding interface configuration script. Each of

these files provide information specific to a particular network interface. See Section 12.2 for more

information on this type of file and what directives it accepts.

Caution

The /etc/sysconfig/networking/ directory is used by the Network Administration Tool

(redhat config network) and its contents should not be edited manually. For more information

about configuring network interfaces using the Network Administration Tool, see the chapter

called Network Configuration in the Official Red Hat Linux Customization Guide.

12.2. Interface Configuration Files

Interface configuration files control the operation of individual network interface device. As your

Red Hat Linux system boots, it uses these files to determine what interfaces to bring up and how to