Friday, August 26, 2011

Appropriate Hardware to study for the RHCSA/RHCE exams

Appropriate Hardware to study for the RHCSA/RHCE exams

Since the 6th edition was released, I've received a number of questions related to the physical hardware needed for people who are studying for their RHCSA/RHCE certs. Yes, in essence, there is an implied hardware requirement. To help answer those questions, I've collected relevant excerpts from my book in this post.

While the Red Hat exams don't test hardware, the RHCSA includes several objectives associated with Kernel-based Virtual Machines (KVM). To meet the RHCE objectives, you'll need to set up multiple systems (which can be on virtual machines), along with knowledge of RHCSA requirements. The packages required to host KVM-based virtual machines are available only on the 64-bit releases of RHEL 6. As Scientific Linux 6 and CentOS 6 use Red Hat source code, KVM-based virtual machines are available only the the 64-bit versions of those distributions as well.

Summary: To meet the objectives associated with the RHCSA/RHCE exams --

1) You should have a 64-bit physical system with hardware virtualization enabled, preferably with multiple CPUs or a CPU with multiple cores
2) You'll need sufficient RAM for at least two virtual machines on the host system (4GB or more would be ideal)
3) While not strictly a hardware requirement, you may want to modify some hardware-related settings to extend the life of some hard drives.

If you're using RHEL 6 (or one of the rebuild distributions such as CentOS-6 or Scientific Linux 6), KVM host software is available only on the 64-bit releases.

As I've noted in the introduction to my book ,

The RHCSA objectives specify a number of points associated with virtual machines. The default RHEL 6 solution uses the Kernel based Virtual Machine (KVM). Red Hat supports KVM as a host only on physical systems with 64-bit CPUs. Therefore, to study for the KVM-related objectives for the RHCSA, you’ll need physical hardware that can handle a 64-bit version of RHEL 6.
In the book, at the end of that paragraph, I made a mistake. 32-bit versions of Scientific Linux 6 do not include KVM host software. That will be noted in the errata. (While you may be able to use 32-bit versions of Fedora for KVM, I haven't tested that. Even if it's possible, it would bring up other problems related to the differences between Fedora and RHEL 6.)

The paragraph that follows is also important, and may also apply to some of you who are studying on desktop systems.

And you should expect to install two or more virtual machines on that 64-bit physical system. Virtual hosts work better on systems with multiple CPUs or systems with multicore CPUs. So to avoid hardware that slows your studies, you’ll want a 64-bit physical system with at least 2GB and preferably 4GB of RAM. (I prepared this book on a 64-bit system with 8GB of RAM.) If you’re using a laptop system, read the information from If the listed bug has not been resolved by the time you read this, the useful lifetime of your hard drive may depend on it.
In Chapter 1, I supplement this discussion with the following information:

If you’re planning to configure VMs on RHEL 6, be sure to choose an architecture that supports hardware-assisted virtualization, along with Basic Input/Output System (BIOS) or Universal Extensible Firmware Interface (UEFI) menu options that allow you to activate hardware-assisted virtualization. A configuration that supports hardware-assisted virtualization will have either the vmx (Intel) or svm (AMD) flags in the /proc/cpuinfo file.

Be aware, RHEL 6 installations on 32-bit systems with UEFI menus are not supported.
While I've looked at just a few hardware systems, published reports suggest that computers with appropriate CPUs from AMD automatically have hardware virtualization enabled. I include the following "On The Job" element that should help if you're shopping for an appropriate system:

If you’re not sure about a system, see if you can try it out at the “store” with one of the “Live CD” distributions. If allowed by store personnel, boot the system from that Live CD (or DVD). Once booted, you should be able to access the /proc/cpuinfo file from the command line. You may need to tinker a bit with the BIOS or UEFI menus. A system configured to support hardware-assisted virtualization will have the vmx or svm flags in that file, even when read from a Live CD distribution.
While there's no "Live CD" of RHEL 6, there are Live CD versions of both Scientific Linux 6 and CentOS 6.

Finally, if you're using a laptop system (some desktop systems may also be affected), be aware that the default Linux settings (including RHEL 6) may result in very frequent cycling of --some-- hard drives. Without changes, hard drives on some systems have been known to last only a few months. For more information, see and . Personally, I've included the following command as a workaround in my /etc/rc.local file:

/sbin/hdparm -B 200 /dev/sda

One common alternative is:

/sbin/hdparm -B 254 /dev/sda



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