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.

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 the Section called /etc/sysconfig/network in Chapter 3.
/etc/sysconfig/network-scripts/ifcfg-<interface-name> — For each network interface 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 the Section called Interface Configuration Files 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.