Intro to Paravirtualization

1
Xen Virtualization
Andrew Hamilton
TJHSST CSL Logo and Powered By Linux by Dan Tran
tjhsst.edu/dtran
2
Presentation Overview

• Theory
• Methods of Virtualizing
• Xen Virtualization
• Conclusion

3
Theory

• Do one thing and do it well (The UNIX philosophy)
• Containerize Systems
• Many little machines contained in one

4
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

5
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

6
Xen Virtualization
7
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

8
Installing a Dom0

• First install and configure the linux
  distribution of 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

9
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

10
VM Networking Bridging
Switch
Network
eth0
Physical Adapter
xenbr0
Network Bridge
Vif0.0
Vif1.0
Vif2.0
VMs
11
VM Networking NAT
Switch
Network
eth0
Physical Adapter
IPTables
NAT/Firewall
Vif0.0
Vif1.0
Vif2.0
VMs
12
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 doesnt fix it now

13
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

14
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

15
Xen Config Files

• kernel /boot/kernel-2.6.29-r1-amd64-xen-domu
• Initrd (if required)
• Memory 512
• Disk phyvgmagellanic/ns1-disk,sda1,w file/
  home/xen/ns1-swap,sda2,w
• Name ns1
• vif 'mac0002C62610B7, mac00163eaa
  bbcc,bridgexenbr1

16
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)

17
Advanced Features

• Live Migration (xm migrate)
• Enable in xend config
• Both servers need to be able to access the VMs
  disks
• Snapshotting for backups
• Using lvm to make consistent backups
• Snapshot the domu from the dom0
• Mount the snapshot and rsync or tar it

18
Conclusion

• Xen can provide a separation of services with
  minimal performance hit
• It is NOT a guaranteed security measure, but its
  pretty good
• Some programs dislike running in VMs
• Allows Virtualization on older x86 hardware

19
A Few Resources

• 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.

20
Any Questions?