Red Hat Enterprise Linux 5 Administration Unleashed

86CHAPTER 3Operating System Updates. Pirut: For adding and removing software.. Pup: Package updater that only shows software updates available from RHN.Before you can use YUM to install or upgrade software, remember you must set it up toconnect to RHN. Either register the system with RHN directly after installation with theSetup Agent (as described in Chapter 2) or at any time by executing the rhn_registercommand. Root access is required, so you will be prompted for the root password if yourun the program as a non-root user.This following sections explain what YUM is, how to use the yum command-line utility,and how to use the two graphical interfaces to YUM included with Red Hat EnterpriseLinux.NOTEAlthough the RHN website might differ from the instructions in this chapter, the YUMutility should be the same as the one described in this chapter.What Is YUM?YUM stands for Yellow dog Updater, Modified because it is based on YUP, the Yellow dogUpdater. Where does the name Yellow dog come from? Yellow Dog is a version of Linux forthe Power Architecture hardware and is RPM-based, just like Red Hat Enterprise Linux andFedora. YUP, and later YUM, were written by the Linux community as a way to maintainan RPM-based system. Fedora Core can be updated with the YUM utility, and, now RedHat Enterprise Linux can be as well starting with Red Hat Enterprise Linux 5.Some of the advantages of YUM include. Automatic resolution of software dependencies. If a package installation or upgraderequest is made and requires the installation or upgrade of additional packages,YUM can list these dependencies and prompt the user to install or upgrade them aslong as they are in a repository YUM is configured to use.. Command-line and graphical versions. The command-line version can be run on asystem with a minimal number of software packages. It also allows administrators towrite scripts to automate software maintenance actions, which can be scheduled attimes convenient for everyone. The graphical versions offer ease-of-use and a userfriendlygraphical interface to software management.. Multiple software locations at one time. YUM can be configured to look for softwarepackages in more than one location at a time. The user doesn’t have to remember toprovide a location each time he performs an action. Software dependencies cansometimes be resolved even if the additional packages are not in the same locationas the requested package.