Certification Objective 2.02-CPU and RAM

Red Hat Enterprise Linux supports computers with Intel and compatible 32-bit and 64-bit processors.

Linux is commonly used as a server operating system. Many server applications can take advantage of the flexibility provided by multiple CPUs. This is known as symmetric multiprocessing (SMP) support. Linux began supporting multiple CPUs with the release of the 2.4 kernel back in 2001. RHEL 5 also supports virtual machines with a customized Xen-based kernel. If you have a newer "dual-core" type CPU, RHEL 5 can even support hardware virtualization, which allows dedicated installations of Microsoft Windows (and other Intel-compatible operating systems) within Linux.

Compatible CPUs

You can install RHEL 5 on systems with a wide variety of CPUs. Red Hat supports six different CPU architectures:

• x86

• Athlon/AMD64 (x86_64)

• Itanium (ia64)

• IBM zSeries

• IBM iSeries

• IBM pSeries

Exam Watch

As of this writing, we assume that Red Hat tests and will continue to test based on the most popular architecture, x86. Other architectures such as Itanium use a different boot loader (ELILO), which is not covered in the Red Hat Exam Prep guide or associated course outlines.

On the Job 

Some developers hope to increase the SMP limit to 128 CPUs. If you're running Linux on an SMP computer, keep up to date with the latest kernel developments at www.kernel.org.

CPUs and Virtualization

Red Hat is in the process of incorporating virtualization in its operating systems. Both Fedora Core 6 and RHEL 5 include Xen, which is a "free virtual machine monitor," which includes QEMU-based emulation to support virtualization similar to VMware.

On the Job 

QEMU is one more alternative for virtualization, licensed under the GPL and the closely related Lesser GPL. Kernel-based Virtual Machine (KVM) technologies require Linux kernel version 2.6.19; RHEL 5 uses 2.6.18. Paravirtualization for VMWare isn't expected until 2.6.21.

There are two kinds of virtualization associated with Xen. Paravirtualization provides a software interface that allows you to install specially ported operating systems (with a Xen-enabled kernel) within software-based virtual machines. Full, or hardware-assisted, virtualization supports direct hardware access; it is limited to certain Intel Dual Core and AMD X2 CPUs.

On the Job 

Not all Intel Dual Core or AMD X2 CPUs support hardware-assisted virtualization. AMD X2 CPUs need to be TL-50 and above; Intel Dual Core CPUs need to be T2300 (or T5600) and above. Furthermore, Intel-based systems are often disabled in the BIOS and may not support hardware-assisted virtualization unless specifically activated through the BIOS menu. If you see the vmx (Intel) or svm (AMD) flags in /proc/cpuinfo, your system supports hardware virtualization.

RAM Requirements

The minimum RAM requirements for RHEL 5 are trivial for today's computers. While you need at least 192MB to install in graphical mode, 64MB is sufficient to install in text mode-and to run this distribution with a text-based login. One advantage of this small footprint is that it allows you to configure more virtual machines using Xen.

On the Job 

In reality, the minimum amount of RAM depends on the amount of shared video RAM. For example, if 64MB of RAM is used for your video system, you need at least 256MB of RAM to install RHEL 5 in graphical mode.