Book Image

KVM Virtualization Cookbook

By : Konstantin Ivanov
Book Image

KVM Virtualization Cookbook

By: Konstantin Ivanov

Overview of this book

Virtualization technologies such as KVM allow for better control over the available server resources, by deploying multiple virtual instances on the same physical host, or clusters of compute resources. With KVM it is possible to run various workloads in isolation with the hypervisor layer providing better tenant isolation and higher degree of security. This book will provide a deep dive into deploying KVM virtual machines using qemu and libvirt and will demonstrate practical examples on how to run, scale, monitor, migrate and backup such instances. You will also discover real production ready recipes on deploying KVM instances with OpenStack and how to programatically manage the life cycle of KVM virtual machines using Python. You will learn numerous tips and techniques which will help you deploy & plan the KVM infrastructure. Next, you will be introduced to the working of libvirt libraries and the iPython development environment. Finally, you will be able to tune your Linux kernel for high throughput and better performance. By the end of this book, you will gain all the knowledge needed to be an expert in working with the KVM virtualization infrastructure.
Table of Contents (15 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Connecting to a running instance with VNC

In this recipe, we are going to connect to a running KVM instance using a VNC client. Once connected, we are going to log in and check the CPU type and available memory of the instance. We've already seen how to start QEMU/KVM instances with VNC support in the previous recipes, but we are going to do it again, in case you are not reading this book from cover to cover.

Virtual Network Computing (VNC) uses the Remote Frame Buffer (RFB) protocol to remotely control another system. It relays the screen from the remote computer back to the client, allowing the full keyboard and mouse control.

There are many different VNC client and server implementations, but for this recipe, we are going to use a freely available version named chicken of the VNC for macOS. You can download the client from

Getting ready

In order to complete this recipe, you will need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe
  • The custom raw Debian image we built in the Installing a custom OS on the image with debootstrap recipe
  • A processor that supports virtualization
  • The loaded KVM kernel modules
  • The chicken of the VNC client, installed, as described in the previous section

How to do it...

  1. Start a new KVM-accelerated qemu instance:
root@kvm:~# qemu-system-x86_64 -name debian -vnc -cpu Nehalem -m 1024 -drive format=raw,index=2,file=debian.img -daemonize    

  1. Ensure that the instance is running:
root@kvm:~# pgrep -lfa qemu    
4987 qemu-system-x86_64 -name debian -vnc -cpu Nehalem -m 1024 -drive format=raw,index=2,file=debian.img -daemonize    
  1. Start the VNC client and connect to the VNC server on the IP address and display port you specified in step 1:

The VNC login screen

  1. Log in to the instance using the root user, then check the CPU type and available memory as shown here:

VNC session

How it works...

In step 1, we started a new QEMU instance with KVM acceleration and enabled a VNC server on it with the specified IP address and display port. We specified the amount of available memory and the CPU model name.

In step 4, we logged in the instance using the root user and the password we created when building the image, then obtained the CPU information by running the lscpu command. Note how the CPU model name matches what we specified with the -cpu flag when we started the virtual machine. Next, we checked the allocated memory with the free command, which also matches what we previously specified with the -m parameter.