Red Hat Enterprise Linux 5 Administration Unleashed

Updating Software 131perform as well as the current kernel, or causes other problems. When you use the -Uargument to RPM, the older version of the software package is no longer available.For most packages, you will receive an error message when trying to use the -i argument toupgrade a package if you already have an older version installed. With the kernel package,you will not receive this error because it is possible to have multiple versions of the kernelinstalled. Thus, it is recommended that you always use the rpm -ivh kernel--..rpm command when upgrading the kernel so the older kernel remainson the system. The system must be rebooted to enable the new kernel. After rebooting, youwill notice the new kernel in the list of possible boot choices. By default, the system bootloader is configured to boot the new kernel. To modify which kernel is booted by default,edit the boot loader configuration file for your architecture. Chapter 2, “Post-InstallationConfiguration,” contains example boot loader files for all architectures.For x86 and x86_64 systems, modify the value of the default option in /etc/grub.conffile. Each kernel installed has a section in /etc/grub.conf starting with a title line such asthe one shown in Listing 5.4. The value of the default option is the number of the titlesection, with the count starting at 0 and going from the first title section listed to thebottom of the file.LISTING 5.4Kernel Section in Bootloader Configuration File5title Red Hat Enterprise Linux (2.6.16-1.2096)root (hd0,0)kernel /boot/vmlinuz-2.6.16-1.2096 ro root=LABEL=/ rhgb quietinitrd /boot/initrd-2.6.16-1.2096.imgIf you are unable to boot the new kernel to modify the bootloader configuration file, youcan choose a different kernel using the up and down arrow keys at the bootloader screenshown as the system is booting and before the kernel is loaded.Updating SoftwareIf an RPM package is already installed, it can be updated to a newer version. With RPM,there isn’t the concept of using a different file or set of files to perform a softwareupgrade. The same RPM file or files used to install a program can be used to update theprogram as well.To update to a newer version of a package already installed:rpm -Uvh --..rpmThe same additional arguments available when installing packages can be used whenupgrading. They are listed in Table 5.1.Some of the files in an RPM package are marked according to what type of files they are.For example, configuration files can be marked as configuration files by the person who