Virtualization on Linux Using KVM and libvirt. Matt Surico Long Island Linux Users Group 11 March, 2014

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Virtualization on Linux

Using KVM and libvirt

Matt Surico

Long Island Linux Users Group 11 March, 2014

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What will we talk about?

● Rationalizing virtualization ● Virtualization basics

● How does it work under Linux? ● Setting up a virtual host

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Why virtualize? - Part 1

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Why virtualize? - Part 2

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Other reasons to virtualize

● Ease of creating new servers (cloning) ● Ad-hoc projects (proof of concept)

● Experimentation with new distributions ● Self-Instructional situations

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Virtualization Architecture

● One key component is the hypervisor.

● A hypervisor is software (or hardware, or even

firmware) that creates an interface between a

guest operating system and a virtual host so that virtual machines can be run.

● The hypervisor's job is to create and/or to

present a virtual operating platform to the virtual machine (an abstraction).

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Hypervisor Diagrams

● We will briefly look at two general types of

hypervisors:

– Native (aka “Bare Metal”, or “Type 1”) – Hosted (aka “Type 2”)

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Bare Metal Hypervisor

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Hosted Hypervisor

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KVM

● Simply put, this allows the Linux kernel to be a

hypervisor

● Has been in the kernel mainline since 2.6.20

● Contains virtualization extensions (Intel VT and

AMD-V), and loadable kernel modules (kvm.ko plus either kvm-intel.ko or kvm-amd.ko)

● Exposes the /dev/kvm interface to a host running

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libvirt

● C library with package bindings for many other languages like

Ruby, Java, python, perl, etc.

● A toolkit for managing virtualization ● Provides:

– Remote management using TLS encryption and x509 certificates

– Remote management authenticating with Kerberos and SASL

– Local access control using PolicyKit

– Zero-conf discovery using Avahi multicast-DNS

– Management of virtual machines, virtual networks and storage

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libvirt diagram

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How to check your CPU

● Use /proc/cpuinfo and look at the flags. There are different flags for Intel vs. AMD

● Intel

– vmx = Intel VT-x (basic virtualization) - required

– ept = Extended Page Tables

– vpid = decreases TLB flushes during context switching between

guests

● AMD

– svm = AMD SVM (basic virtualization) - required

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Building the demo

● We'll take a brief walk through the steps taken to

prepare the laptop for today's demo

– Verify the CPU will work – Add storage to laptop

– Install CentOS 6.4 (the host OS) – Include virtualization packages

● Once these steps are done, virtual machines can

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Build: CPU/RAM

● The CPU in the laptop is AMD A4-3305M (dual core, 800 MHz, 512 KB cache) ● The command used to check the processor was:

[matt@aquila ~]$ grep flags /proc/cpuinfo | uniq

flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx

mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nonstop_tsc extd_apicid aperfmperf pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt cpb npt lbrv svm_lock nrip_save pausefilter

● Laptop has 3 GB RAM

● FYI: Home machine (dedicated virtual host) has Intel(R) Core(TM) i5-3570K CPU,

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Build: Adding storage

● Laptop has a single internal hard drive, dual boot

Ubuntu 13.04 and “a certain proprietary OS that came with the laptop.”

● Current hard drive didn't have enough space to setup

a third operating system plus the virtual disks for multiple VMs

● Used an external USB 3.0 drive (500 GB)

● Allows for total removal of the storage to operate the

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Build: Partitioning storage

During the installation of CentOS 6.4, the external drive showed up as /dev/sdb, so it was partitioned as such:

● /dev/sdb1 = /boot (1 GB) ● /dev/sdb2 = swap (4 GB)

● /dev/sdb3 = Physical Volume for LVM (the rest of the

drive)

– vg_kvm = Volume Group (~460 GB) – 334 GB allocated to logical volumes

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Build: Logical Volumes

[matt@aquila ~]$ sudo lvs vg_kvm LV VG Attr LSize libvirtKVMLV vg_kvm -wi-ao--- 300.00g rootKVMLV vg_kvm -wi-ao--- 15.00g usrKVMLV vg_kvm -wi-ao--- 15.00g varKVMLV vg_kvm -wi-ao--- 4.00g

● /dev/mapper/vg_kvm-libvirtKVMLV on /var/lib/libvirt type ext4 ● /dev/mapper/vg_kvm-rootKVMLV on / type ext4

● /dev/mapper/vg_kvm-usrKVMLV on /usr type ext4 ● /dev/mapper/vg_kvm-varKVMLV on /var type ext4

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Build: CentOS installation

● CentOS 6.4 installed with “Virtual Host”

profile.

● Also added some other graphical

convenience packages

● Important: under Virtualization, pick

“Virtualization Tools”

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Working with VMs

Several Open Source tools available:

● virsh: command line, provided by libvirt ● Virtual Machine Manager: GUI

● oVirt: web application

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Networking

● One or more virtual networks may be

created within the virtual host

● Virtual machines may be outfitted with one

or more virtual NICs

● The dnsmasq lightweight server provides

DNS and DHCP services for the virtual network

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Networking: libvirt

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Time for a demo!

What we'll see:

● Use of virsh and virt-manager

● Creating and managing VMs (including

cloning)

● Creating and managing virtual networks ● Provisioning additional storage for VMs