Chapter 14: 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 explores 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 to resolve hostnames on small networks with no DNS server. 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.

/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 provides information specific to a particular network interface. See the “Interface Configuration Files” section of this chapter for more information on this type of file and what directives it accepts.

Warning

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 Chapter 13.