Red Hat Enterprise Linux 5 Administration Unleashed

66CHAPTER 2Post-Installation Configuration. /etc/resolv.conf file: Sets the DNS servers (using their IP addresses) and the searchdomain. The values of the DNS servers are often added when the network is activatedbecause the data can be provided by DHCP or a similar service.. /etc/sysconfig/network-scripts/ directory: Contains scripts to start and stop anetwork device and a specialized configuration file for each device.. /etc/rc.d/init.d/network file: Initialization script that starts and stops thenetwork.CAUTIONIf the Graphical Network Configuration Tool from the Administration, Network menuitem of the System menu has ever been run on the system, an /etc/sysconfig/networking/ directory will exist. The files in this directory are only used by the graphicaltool and are not referenced by any of the network scripts. If changes are made tothese files, they will not be applied to the actual network configuration files used.Some of the network configuration files such as the ifup and ifdown scripts in /etc/sysconfig/network-scripts/ do not need to be modified in most cases and should notbe modified unless absolutely necessary. This section discusses the network configurationfiles that may be modified to change the network settings and how to enable the changes.Listing 2.1 shows an example of a /etc/modprobe.conf file. The first line assigns the e100kernel module to the eth0 network device. If the network card is supported, the module isautomatically configured during installation or by Kudzu the first time the system isbooted with the new card. Refer to Chapter 6, “Analyzing Hardware,” for more detailedinformation about how Kudzu works, how to add module parameters to the/etc/modprobe.conf file, or how to change which kernel module is used for each device.LISTING 2.1/etc/modprobe.confalias eth0 e100alias scsi_hostadapter sata_silalias scsi_hostadapter1 ata_piixThe /etc/sysconfig/network file usually contains the content shown in Listing 2.2. If theNETWORKING option is set to yes, the networking subsystem is enabled but not necessarilystarted at boot time. The value of the HOSTNAME option is the hostname for the system. Ifone is not set, the default hostname is localhost. Refer to the file /usr/share/doc/initscripts-/sysconfig.txt for additional options for this file.LISTING 2.2/etc/sysconfig/networkNETWORKING=yesHOSTNAME=smallville