intro to para virtualization

8/3/2019 Intro to Para Virtualization

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Xen VirtualizationAndrew Hamilton

TJHSST CSL Logo and Powered By Linux by Dan Tran tjhsst.edu/~dtran



Presentation Overview

• Theory

• Methods of Virtualizing

• Xen Virtualization• Conclusion



Theory

• Do one thing and do it well (The UNIX philosophy)

• Containerize Systems

•

Many little machines contained in one



Methods of Virtualization

• Chroots

– Minimal Overhead

– One kernel, network connection, process system

– Root can break out

• FreeBSD Jails / Solaris Containers

– Separate Networking and process systems, root is

trapped

– Overhead is still minimal

– Still only one kernel



More Methods of Virtualization

• Full Virtualization

– Multiple OSes, complete segregation of resources

– High overhead, oftentimes expensive

• Paravirtualization (Xen/LDOMs)

– Multiple Oses with less overhead

– May require specialized hardware or a modified

operating system



Xen Virtualization



What we have

• Hypervisor

– Runs underneath everything and serves as an

interface between the hardware and the VMs

– The Xen part of Xen Virtualization

• Dom0

– Generally a linux kernel with the xen patches

– Is able to control the hypervisor and manage VMs

– Needs drivers for the server hardware

• DomUs

– The VMs we want to run



Installing a Dom0

•

First install and configure the linux distributionof your choice

• Then install the xen-specific packages

–

Debian: apt-get install xen-linux-image – Gentoo: emerge xen, xen-tools, xen-sources

– Red Hat: yum install xen kernel-xen



Configuring the Dom0

• Grub

– Boot using the Xen hypervisor as the kernel

– Load the Dom0 Kernel as a Module

– Start xend on boot• VM Storage Space

– Local vs SAN

–

Files or LVM (or other devices)• Setup VM Networking

– Bridging or NAT



VM Networking: Bridging

Switch

eth0

xenbr0

Vif0.0 Vif1.0 Vif2.0

Network Bridge

Physical Adapter

Network

VMs



VM Networking: NAT

Switch

eth0

IPTables

Vif0.0 Vif1.0 Vif2.0

NAT/Firewall

Physical Adapter

Network

VMs



Testing Time!

• Reboot to the Xen Setup (hopefully it boots)

• Stress Test the new setup

– Recompiling the kernel repeated works well

– For a in `seq 1 20`; do make clean; make; done;

• Make sure everything works well now

•

If it doesn’t fix it now



Creating VMs

• Manual or automatic?

– Xen-tools

• File-based vs Device-based

• Create the harddrives

– LVM create the logical volumes

– Files, create the files

• Format the disks



Linux VMs

• Mount the hard-drives

• Use an appropriate method to install your OS

– Debootstrap

– Untar and chroot

– Copy over an image

• Remember VMs only need a small set of

packages



Xen Config Files

• kernel = ‘/boot/kernel-2.6.29-r1-amd64-xen-domu

• Initrd (if required)

•

Memory = ‘512’ • Disk = [ ‘phy:vgmagellanic/ns1-

disk,sda1,w’ file:/home/xen/ns1-

swap,sda2,w’ ]

• Name = ‘ns1’

• vif = [ 'mac=00:02:C6:26:10:B7‘,

‘mac=00:16:3e:aa:bb:cc,bridge=xenbr1’ ]



Managing VMs

• Starting VMs (xm create)

– We usually want to be running VMs

• Stopping VMs (xm shutdown)

– This is the nice safe way to stop VMs

• Really Stopping VMs (xm destroy)

– The Xen equivalent of a four-second off

• Monitoring (xm list, xm top)



Advanced Features

• Live Migration (xm migrate)

– Enable in xend config

– Both servers need to be able to access the VM’s

disks

• Snapshotting for backups

– Using lvm to make consistent backups

– Snapshot the domu from the dom0

– Mount the snapshot and rsync or tar it



Conclusion

• Xen can provide a separation of services with

minimal performance hit

• It is NOT a guaranteed security measure, but

it’s pretty good

• Some programs dislike running in VMs

• Allows Virtualization on older x86 hardware



• http://tjhsst.edu/~ahamilto/josti09/

This Presentation

• http://tjhsst.edu/admin/livedoc/

– Sysadmin Livedoc, lots of general knowledge about

Linux/UNIX

• http://www.xen.org

– Homepage of the Xen project.

A Few Resources

http://www.xen.org/

http://www.xen.org/

http://www.xen.org/



Any Questions?

intro to para virtualization

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