Red Hat Enterprise Linux 5 Administration Unleashed

530APPENDIX BCreating Virtual Machines. Dedicated resource allocation. Each VM is allocated specific resources so one can’tuse 100% of the resources and cause the others to slow down or stop responding.. Multiple OSes or OS versions. One system can run multiple OSes or differentversions of the same OS, converting one test system into multiple test systems forsoftware development.This appendix guides the reader through the process of creating VMs, starting and stoppingVMs, and managing them with the virtualization tools.Virtualization System RequirementsThe host system must use the GRUB boot loader, which is the default for Red HatEnterprise Linux. It is required to be able to boot into the Virtualization guests.CAUTIONThe Virtualization feature of Red Hat Enterprise Linux will not work if SELinux isenabled. Refer to Chapter 23, “Protecting Against Intruders with Security-EnhancedLinux,” for instructions on disabling it before continuing.Before installing and configuring the Virtualization feature, be sure you have enoughsystem resources for each virtual machine. The system resources for each VM must be inaddition to the system resources needed for the host machine. The additional disk spacerequirements for each virtual machine are the same as those for a Red Hat EnterpriseLinux install. The amount of disk space necessary depends on the type of system you areconfiguring. Approximately 4 GB is recommended as a minimum.A disk partition or a disk image file can be used as the virtual disk space. The disk image iscreated during setup if it does not already exist, so the disk space for it just needs to bepart of the existing mounted filesystem. To use a disk partition, create it first and thenfollow the steps for creating a VM. At least 500 MB of RAM is recommended for eachvirtual guest, possibly more depending on the desired function of the guest.CAUTIONRed Hat Enterprise Linux 5 includes version 3 of the xen RPM package. It is notcompatible with virtual guests set up with previous versions of this package.Currently, Virtualization only runs as a supported feature on x86 and x86_64 systems.Virtualization for the Itanium2 is also available with Red Hat Enterprise Linux 5 but isonly offered as a technology preview. To run Virtualization on an x86 system, the processormust have Physical Address Extension (PAE) support. To determine if your processorhas PAE support, look for the pae flag in the list of flags for the processor in the /proc/cpuinfo virtual file. To only display the line of flags, use the command cat /proc/cpuinfo | grep flags, which shows a line similar to the following:flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca \cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm up