Some good wireless networking training- free

Aruba makes a nice lightweight access point (LWAP). Centrally managed from a central point. Part of their magic is a GRE tunnel from AP to controller, so the controller can do all kinds of nifty tricks with/to the wireless client packets.

Here is some network training that is has some free options:

Free Wireless Training

Some is Aruba specific (hello mounting Aruba hardware). But the networking fundamentals course is vendor agnostic and has some good information.

Ever wondered why 802.11b clients slow down 802.11g networks, then do the networking fundamentals:

http://www.arubanetworks.com/education/networking_fundamentals.php

It does a review of basic networking, covers wireless and security basics. Self paced in wmv and mov formats.

The other training courses are more Aruba-centric.

Xen Virtualization on CentOS

You can use many tools on Centos 5 to manage virtual servers:

CLI tools: xm, install-sh, virsh
GUI tools: virt-manager

Here are some useful links-

How to install a virtual server (after installing CentOS with the Virtualization packages):
http://wiki.centos.org/HowTos/Xen/InstallingCentOSDomU

That is a command line tutorial. But you could use virt-manager if you have X and Xen. It walks you though all the steps in a much easier way, but it is a good idea to know what is going on behind the scenes. Everything in this tutorial can be done by virt-manager without much hassle.

This is how you install a native virtualization DomU like Windows:

http://wiki.centos.org/HowTos/Xen/InstallingHVMDomU

It also has the way to check your processor extensions.

This one has some basics about keyboard mapping and also has how to deal with SELinux (without turning it off people!):

http://wiki.centos.org/TipsAndTricks/Xen

This article has P2V basics. It gives some insight into what the virt-p2v boot iso (linked in the intro post) does behind the scenes:

http://wiki.centos.org/HowTos/Xen/MoveNative2DomU

And if you had to move something yourself if you had to do it manually.

Free Virtualization Introduction

Xen on Linux is usable out of the box now. If you download CentOS 5.1 (or later I would guess), you can setup virtualization during install.

Virtualization lets you run multiple instances of an operating system and applications on one piece of hardware. You can imagine or read on the net why that would be useful.

Some terms to translate for those familiar with VMWare or Parallels style terminology:

Host OS: VMWare Server (not ESX) uses an operating system (windows or linux) as a host, ESX is the host, and Parallels uses OS X. With Xen virtualization this roughly corresponds to Domain0. Domain0 has unlimited privileges.

Guest OS: You can run windows, linux or other operating systems under VMWare or Parallels. On Xen the guest OS is known as a DomU (domain U), which has direct access to hardware. This domain has limited resources (ram and processors as configured), by default it has no access to hardware.

Paravirtualization vs. fully virtualized-

paravirtualization uses software to allow virtualization. Under CentOS 5, the paravirtualizable guest operating systems are basically linux, linux and linux. Native virtualization uses processor extensions so you need a recent Intel processor that supports or a AMD that supports AMD-V extensions. The extensions aren't very common outside of server class chips (Xeon and Opteron). Here is how to tell if you have the extensions:

egrep '^flags.*(vmx|svm)' /proc/cpuinfo

If you don't have a lines of output with vmx or svm in them, you don't have the extensions.

P2V: Physical to Virtual. How to import physical servers (usually old), to a virtual machine, which can save you time and money and get you out of supporting old and busted servers. There are some pay tools for P2V for Xen and Linux. But here is a pretty good free one:

http://et.redhat.com/~rjones/virt-p2v/

That is it for the intro. More tomorrow with specific examples.

system-config-netboot

Redhat, time for your verbal beating. RHEL3 and 4 I love you. RHEL 5 you are obviously rushed out the door. Proper XEN support starts in 5.1. But the real symptom of the this rush is:

PXE boot.

That is right. The Doc guide used to have directions on PXE boot/network install for RHEL5. It mentioned system-config-netboot (which wasn't in RHEL5). So instead of fixing system-config-netboot somebody went and trashed the doc excising references to system-config-netboot, but not the whole section and not the references to the pxeos tool which is part of the package.

Well if you are lazy like me, and like the tool to setup the /tftpboot directory and not to have to remember anything but the /etc/dhcpd.conf commands:

You can use the system-config-netboot from Fedora 8 (which was kind of a pain to find- thanks to all the mirrors that haven't mirrored FC8 as of this article) right on RHEL 5.1 (for sure, tested, it works).

My favorite property of RHEL is the kickstart/PXE boot ease of deployment. An afternoon or two of fun and you can deploy 1000s or 10,000s of boxes with no trouble. Unless of course you can't get system-config-netboot to setup your PXE environment for you... because it isn't on the distribution.

There is a ticket on bugzilla.redhat.com that says it will be in RHEL5.2. Which will be nice.