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KVM Virtualization Cookbook
KVM Virtualization Cookbook

KVM Virtualization Cookbook: Learn how to use KVM effectively in production

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Profile Icon Konstantin Ivanov
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Profile Icon Konstantin Ivanov
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Paperback Jun 2017 340 pages 1st Edition
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KVM Virtualization Cookbook

Using libvirt to Manage KVM

In this chapter, we will cover the following topics:

  • Installing and configuring libvirt
  • Defining KVM instances
  • Starting, stopping, and removing KVM instances
  • Inspecting and editing KVM configs
  • Building new KVM instances with virt-install and using the console
  • Managing CPU and memory resources in KVM
  • Attaching block devices to virtual machines
  • Sharing directories between a running VM and the host OS
  • Autostarting KVM instances
  • Working with storage pools
  • Managing volumes
  • Managing secrets

Introduction

In the previous chapter, we saw examples of provisioning virtual machines using the QEMU toolset and the KVM kernel modules. The QEMU commands are convenient for quickly starting virtual instances; however, they don't provide an easy way of configuring and administering the life cycle of the virtual machines.

In this chapter, we are going to work with the libvirt toolset. Libivrt provides various userspace commands and language bindings in order to build, configure, start, stop, migrate, terminate, and do other functions to manage your virtual machines. It provides support for different virtualization technologies, such as QEMU/KVM, XEN, and containers with LXC.

We will start by installing and configuring the libvirt tools, then move on to creating virtual machines using the XML configuration files that libvirt supports and explore many of the functionalities...

Installing and configuring libvirt

In this recipe, we are going to install libvirt from packages provided by the Linux distribution of choice and see what configuration files and options are available for configuring it. As with any other production-ready tools, we recommend using packages for your production environment for ease and consistency of deployment; however, compiling the latest version from the source is also an option if the packages from your Linux vendor are older.

Getting ready

Depending on your Linux distribution, the package name and installation commands will differ. You can use your system's package manager, such as apt, dnf, or yum to search for any packages containing the libvirt string and get familiar...

Defining KVM instances

In this recipe, we are going to define a virtual instance by creating a simple XML configuration file that libvirt can use to build the virtual machine. We are going to describe some of the XML schema blocks and look at examples of how to generate the XML definition file using the virt-install command rather than writing it manually.

Getting ready

For this recipe, we are going to need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe from Chapter 1, Getting Started with QEMU and KVM.
  • The custom raw Debian image we built in the Installing a custom OS on the image with debootstrap recipe from the previous chapter.
You can use your own virtual machine...

Starting, stopping, and removing KVM instances

In the previous recipe, we saw how to define new KVM virtual machine by either manually writing the XML definition file or using the virt-install tool to define the instance for us.

If you define a new instance from an XML file, by default the instance will not start automatically. In this recipe, we will see how to start an instance that was previously configured.

Getting ready

For this recipe, we are going to need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe from Chapter 1, Getting Started with QEMU and KVM.
  • The custom raw Debian image we built in the Installing a custom OS on the image with debootstrap recipe from the...

Inspecting and editing KVM configs

In this recipe, we are going to use the virsh tool to inspect and edit the configuration for an existing virtual machine. As we saw earlier, once we define and start a KVM instance, libvirt creates the XML definition file in the /etc/libvirt/qemu/ directory. We can dump the guest configuration to disk, for inspection, or to back it up. With the virsh command we can also perform updates to the configuration in place, as we will see later in this recipe.

Getting ready

For this recipe, we are going to need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe from Chapter 1, Getting Started with QEMU and KVM
  • The custom raw Debian image we built...

Building new KVM instances with virt-install and using the console

In the Connecting to the running instance with VNC recipe from Chapter 1, Getting Started with QEMU and KVM, you learned how to connect to a QEMU/KVM virtual machine that was running a VNC server. This is a great way to connect to an instance that is being installed or in the process of booting in order to interact with it.

So far, we've used the custom raw image that we created earlier, which contains an installation of Debian. Recall from Chapter 1, Getting Started with QEMU and KVM, that we used the debootstrap command to install the OS inside the image file. In this recipe, we are going to use the virt-install tool to install a new Linux distribution, using the provided upstream Internet repository, as the source of the installation and then use the virsh command to attach to the running instance, using...

Introduction


In the previous chapter, we saw examples of provisioning virtual machines using the QEMU toolset and the KVM kernel modules. The QEMU commands are convenient for quickly starting virtual instances; however, they don't provide an easy way of configuring and administering the life cycle of the virtual machines.

In this chapter, we are going to work with the libvirt toolset. Libivrt provides various userspace commands and language bindings in order to build, configure, start, stop, migrate, terminate, and do other functions to manage your virtual machines. It provides support for different virtualization technologies, such as QEMU/KVM, XEN, and containers with LXC.

We will start by installing and configuring the libvirt tools, then move on to creating virtual machines using the XML configuration files that libvirt supports and explore many of the functionalities that the toolkit provides in order to manage the life cycle of KVM instances. All the recipes in this chapter are going...

Installing and configuring libvirt


In this recipe, we are going to install libvirt from packages provided by the Linux distribution of choice and see what configuration files and options are available for configuring it. As with any other production-ready tools, we recommend using packages for your production environment for ease and consistency of deployment; however, compiling the latest version from the source is also an option if the packages from your Linux vendor are older.

Getting ready

Depending on your Linux distribution, the package name and installation commands will differ. You can use your system's package manager, such as apt, dnf, or yum to search for any packages containing the libvirt string and get familiar with what is available for your particular Linux variant. The source code can be downloaded from the official libvirt project website at http://www.qemu-project.org/download/#source.

How to do it...

To install libvirt from packages and source follow the following steps:

  1. On...

Defining KVM instances


In this recipe, we are going to define a virtual instance by creating a simple XML configuration file that libvirt can use to build the virtual machine. We are going to describe some of the XML schema blocks and look at examples of how to generate the XML definition file using the virt-install command rather than writing it manually.

Getting ready

For this recipe, we are going to need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe from Chapter 1, Getting Started with QEMU and KVM.
  • The custom raw Debian image we built in the Installing a custom OS on the image with debootstrap recipe from the previous chapter.

Note

You can use your own virtual machine image or download one from the Internet, as we showed in the Using pre-existing images recipe in Chapter 1, Getting Started with QEMU and KVM.

How to do it...

To define a new KVM virtual machine, run the commands outlined here:

  1. List all virtual machines on the host OS:
root...

Starting, stopping, and removing KVM instances


In the previous recipe, we saw how to define new KVM virtual machine by either manually writing the XML definition file or using the virt-install tool to define the instance for us.

If you define a new instance from an XML file, by default the instance will not start automatically. In this recipe, we will see how to start an instance that was previously configured.

Getting ready

For this recipe, we are going to need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe from Chapter 1, Getting Started with QEMU and KVM.
  • The custom raw Debian image we built in the Installing a custom OS on the image with debootstrap recipe from the previous chapter.
  • The virsh tool provided by completing the Installing and configuring libvirt recipe.
  • The defined instance from the Defining KVM instances recipe in a shut off state.

How to do it...

The following steps outline the process of listing, starting, and stopping KVM...

Inspecting and editing KVM configs


In this recipe, we are going to use the virsh tool to inspect and edit the configuration for an existing virtual machine. As we saw earlier, once we define and start a KVM instance, libvirt creates the XML definition file in the /etc/libvirt/qemu/ directory. We can dump the guest configuration to disk, for inspection, or to back it up. With the virsh command we can also perform updates to the configuration in place, as we will see later in this recipe.

Getting ready

For this recipe, we are going to need the following:

  • The QEMU binaries, provided after following the Installing and configuring QEMU recipe from Chapter 1, Getting Started with QEMU and KVM
  • The custom raw Debian image we built in the Installing custom OS on the image with debootstrap recipe from the previous chapter, or any other virtual machine image, in either raw or qcow2 format
  • The virsh tool provided by completing the Installing and configuring libvirt recipe
  • A running libvirt KVM instance

How...

Building new KVM instances with virt-install and using the console


In the Connecting to the running instance with VNC recipe from Chapter 1, Getting Started with QEMU and KVM, you learned how to connect to a QEMU/KVM virtual machine that was running a VNC server. This is a great way to connect to an instance that is being installed or in the process of booting in order to interact with it.

So far, we've used the custom raw image that we created earlier, which contains an installation of Debian. Recall from Chapter 1, Getting Started with QEMU and KVM, that we used the debootstrap command to install the OS inside the image file. In this recipe, we are going to use the virt-install tool to install a new Linux distribution, using the provided upstream Internet repository, as the source of the installation and then use the virsh command to attach to the running instance, using the console.

Getting ready

For this recipe, we are going to need the following:

  • The virsh command
  • The virt-install command...

Managing CPU and memory resources in KVM


Changing the amount of allocated memory or the number of CPUs can be done either by editing the XML definition for the VM or using the libvirt toolset. In this recipe, we are going to look at examples of changing both the memory and the CPU count for a KVM instance.

Getting ready

For this recipe, we are going to need the following:

  • A running KVM instance with 1 GB of memory, 1 CPU allocated, and console access
  • The libvirt package
  • A guest OS with at least 4 GB of available memory and minimum of 4 CPUs

How to do it...

To inspect and update the memory and CPU resources assigned to a virtual machine follow the process outlined here:

  1. Get memory statistics for the running instance:
root@kvm:~# virsh dommemstat kvm1
actual 1048576
swap_in 0
rss 333644

root@kvm:~#
  1. Update the available memory for the VM to 2 GB:
root@kvm:~# virsh setmem kvm1 --size 1049000

root@kvm:~#
  1. Stop the running instance:
root@kvm:~# virsh destroy kvm1
Domain kvm1 destroyed

root@kvm:~#
  1. Set the...
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Key benefits

  • - Build, manage and scale virtual machines with practical step-by-step examples
  • - Leverage the libvirt user-space tools and libraries to manage the life-cycle of KVM instances
  • - Deploy and scale applications inside KVM virtual machines with OpenStack

Description

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.

Who is this book for?

If you are a system administrator working KVM virtualization, this book will help you grow on your expertise of working with the infrastructure to manage things in a better way. You should have a knowledge of working with Linux based systems.

What you will learn

  • - Deploy different workloads in isolation with KVM virtualization and better utilize the available compute resources
  • - Explore the benefits of running applications with KVM and learn to prevent the “bad-neighbor” effect
  • - Leveraging various networking technologies in the context of virtualization with Open vSwitch and the Linux bridge.
  • - Create KVM instances using Python and inspect running KVM instances
  • - Understand Kernel Tuning for enhanced KVM performance and better memory utilization

Product Details

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Publication date : Jun 16, 2017
Length: 340 pages
Edition : 1st
Language : English
ISBN-13 : 9781788294676
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Length: 340 pages
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Language : English
ISBN-13 : 9781788294676
Languages :
Tools :

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Table of Contents

8 Chapters
Getting Started with QEMU and KVM Chevron down icon Chevron up icon
Using libvirt to Manage KVM Chevron down icon Chevron up icon
KVM Networking with libvirt Chevron down icon Chevron up icon
Migrating KVM Instances Chevron down icon Chevron up icon
Monitoring and Backup of KVM Virtual Machines Chevron down icon Chevron up icon
Deploying KVM Instances with OpenStack Chevron down icon Chevron up icon
Using Python to Build and Manage KVM Instances Chevron down icon Chevron up icon
Kernel Tuning for KVM Performance Chevron down icon Chevron up icon

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