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 Dom0 DomUs
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 VM Storage Space Setup VM Networking
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 eth0 IPTables Vif0.0 Vif1.0 Vif2.0 Network
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 doesn’t fix it now

13. Creating VMs Manual or automatic? File-based vs Device-based
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 = [ ‘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’ ]

16. Managing VMs Starting VMs (xm create) Stopping VMs (xm shutdown)
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) Snapshotting for backups
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

18. 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

19. A Few Resources http://tjhsst.edu/~ahamilto/josti09/
This Presentation
Sysadmin Livedoc, lots of general knowledge about Linux/UNIX
Homepage of the Xen project.

20. Any Questions?