I was setting up a hypervisor for RHEV running a full RHEL6 install instead of RHEV-H, and I wanted to tune it for better hypervisorness.

So I thought, Hey! I'll install tuned, since I am all excited about tuned after viewing the slides from Mark Wagner's Achieving Top Network Performance (PDF) at the 2012 Red Hat Summit. I was particularly excited about slide 12 entitled "Teaser 3 - latency."

I restarted a standalone KVM host running RHEL6 and when I opened Virtual Machine Manager, my guest virtual machine wasn't listed at all.

Eek!

Turns out I had been messing around with the XML definition in /etc/libvirt/qemu/machinename.xml (I know, I know...consider my hand slapped) and broke it. Fortunately /var/log/libvirt/libvirtd.log was kind enough to let me know what went wrong:

My use case was pretty simple. I wanted to share out a raw device via iSCSI to a nearby host on the 172.16.2.x network.

In addition to a minimal Red Hat Enterprise Linux 6 (or equivalent) install, a few packages are needed:

I knew the device I wanted to share was /dev/sdb by looking at the output from dmesg:

When Red Hat Enterprise Virtualization Manager for Servers is installed, it offers to configure iptables for you:

Here's an annotated version of what the RHEVM installer will give you: