Red Hat Enterprise Linux 5 Administration Unleashed

Installing Virtualization 531There are two types of virtualization: para-virtualization and full virtualization. Paravirtualizationcreates a VM for the guest OS, but the virtual hardware is not exactlyidentical to the actual physical hardware. An OS run inside a para-virtualized VM mustsupport para-virtualization so that the virtual hardware is recognized. For example, withVirtualization, the disk image used as the virtual hard drive has the device name xvda.On a fully virtualized system, the hardware is simulated so that the guest OS does nothave to support virtualization. For example, the virtual hard drive for a VM on a fullyvirtualized host uses the device name sda for the first SCSI hard drive so that the guest OSis unaware that it is running inside a VM. It is slower than para-virtualization.Para-virtualization can be run on the x86_64 and Itanium2 architectures and x86 systemwith the PAE extension. To achieve full virtualization, the processor on the host systemmust be 64-bit (x86_64 or Itanium2) and must have a Hardware Virtual Machine (HVM)layer referred to as vmx for Intel processors and svm for AMD processors. Check the list offlags in /proc/cpuinfo for the flag corresponding to your 64-bit processor. If you do notfind it, be sure this feature has been enabled in the BIOS.Installing VirtualizationThe Virtualization feature can be installed during the installation process or after it. Toinstall it while installing the operating system, enter an installation code that includesvirtualization support. This code should have been provided with your Red Hat EnterpriseLinux subscription if you elected to purchase the virtualization feature. To verify that theinstallation will include the Virtualization packages, select to customize the software selection.On the next screen, the Virtualization software group should appear and should beselected as shown in Figure B.1. This software group is only shown if an installation codethat includes virtualization is entered at the beginning of the installation program.BTo install Virtualization after the initial installation process is complete, first subscribe thesystem to the Virtualization channel in Red Hat Network. It will be listed as a childchannel of the Red Hat Enterprise Linux 5 channel for the system. Go to rhn.redhat.comto perform this action and for detailed instructions on subscribing to additional channels.After the system has access to the Virtualization channel, use yum to install the necessarypackages. As root, execute the following where is a space-separated list ofpackage names:yum install Alternatively, schedule the package installation via the RHN website. The following packagesare necessary to configure Virtualization (additional packages will be installed asdependencies):. kernel-xen: Linux kernel with Virtualization support compiled into it.. xen: Virtualization tools needed to set up and maintain the virtual machines.. xen-libs: Libraries necessary for the Virtualization applications.