Red Hat Enterprise Linux 5 Administration Unleashed

Performing an Upgrade 55Configuring the DHCP ServerIf you do not already have a DHCP server setup on your network, consult Chapter 14,“Granting Network Connectivity with DHCP,” for details. The lines in Listing 1.3 must bein the dhcpd.conf file to enable PXE booting. Replace with the IPaddress or hostname of the PXE server.1LISTING 1.3Enabling PXE Booting on the DHCP Serverallow booting;allow bootp;class “pxeclients” {match if substring(option vendor-class-identifier, 0, 9) = “PXEClient”;next-server filename “linux-install/pxelinux.0”;}Starting the PXE Network InstallationTo start the PXE installation, configure the client to boot via PXE. This step varies per system,so consult your motherboard or network card documentation for details. Then, boot thesystem and wait for the first installation screen to appear. Follow the steps in the “Performingthe Installation” section earlier in this chapter to finish the installation. If performing a kickstartinstallation, wait for the installation to complete and reboot the system.Performing an UpgradeIf the system already has an older version of Red Hat Enterprise Linux installed, it can beupgraded, preserving the data on the system while upgrading the packages to the latestversions.To perform an upgrade, either choose Upgrade an existing installation during the interactiveinstallation or use the upgrade directive in the kickstart file.CAUTIONEven if you are not reformatting partitions with data that needs to be preserved, it isimportant that you back up all data before performing the upgrade in case an erroroccurs.When performing an upgrade, the steps are similar to those described in the “Performingthe Installation” section earlier in this chapter. However, some screens are omittedbecause their operations are not permitted for upgrades. For example, the system cannotbe repartitioned because it would cause data loss.