Red Hat Enterprise Linux 5 Administration Unleashed

236CHAPTER 10Techniques for Backup and RecoveryTIPIf using NFS, FTP, or HTTP, remember to allow the system being booted into rescuemode access to the directory containing the installation files.If you select NFS, FTP, or HTTP, a network connection will be established, if possible,before continuing. If the location does not require a network connection, rescue modeoptionally allows the administrator to start a network connection. After choosing whetherto start the network, select whether to mount the filesystem. As with using rescue modefrom the installation CD or DVD, use the shell to repair the system, and type exit toreboot the system when finished.Single-User ModeSingle-user mode is equivalent to runlevel 1 on the system. If runlevel 1 is not configuredproperly, you will not be able to boot into single-user mode. Rescue mode requires a bootmedia, but single-user mode is specified as a kernel option using the installed boot loaderand does not require additional boot media. However, it does require that the boot loaderis working properly and that the filesystem be mounted. It does not provide the ability tostart a network connection.Possible reasons to use single-user mode include. Forgot root password. Repair runlevel other than runlevel 1To boot into single-user mode, boot the system with the single kernel parameter.Specifying a boot parameter differs from architecture to architecture. Refer to Table 10.6to determine the correct method for your architecture.TABLE 10.6 Booting into Single-User Mode per ArchitectureArchitectureSingle-User Mode Commandx86, x86_64 Press any key at the Booting Red Hat Enterprise Linux() message to view the GRUB menu. Pressthe E key to edit the currently selected boot line. Append the linewith the word single, and press B to boot the system.Intel ItaniumAt the EFI shell prompt, type elilo linux single.IBM POWERAppend a space and the number 1 after the kernel name at(IBM eServer iSeries, YABOOT prompt.IBM eServer pSeries)IBM System zCreate another boot stanza in /etc/zipl.conf identical to thedefault stanza except append a space and the number 1 at theend of the parameters. Refer to Chapter 2, “Post-InstallationConfiguration,” for a sample /etc/zipl.conf file.Be sure to run the /sbin/zipl command as root to enable thechange.