VMs Virtual Machines

VM What is a VM  Virtual Machine  Software implementation of a machine running on another machine May or may not resemble the host machine E.g.  Linux on a Windows machine  Windows on Windows  MVS on VM (IBM)

Why VMs Emulate software or hardware you don’t have on hand  Reduce costs Reduce exposure  In a hostile environment If machine becomes infected Reboot VM  Test new environments If mess up, just reboot VM Isolate programs/environments Adjust loads  Move/Start new VM’s to new/different servers as needed

VMWare View of Benefits Compatibility:  Virtual machines are compatible with all standard x86 computers Virtual machines are compatible with all standard x86 computers Isolation:  Virtual machines are isolated from each other as if physically separated Virtual machines are isolated from each other as if physically separated Encapsulation:  Virtual machines encapsulate a complete computing environment Virtual machines encapsulate a complete computing environment Hardware independence:  Virtual machines run independently of underlying hardware Virtual machines run independently of underlying hardware

VM downside More complicated environment Need to be aware of licensing issues Virtual machine might not 100% emulate a physical machine Performance Extra cost of the VM software

Brief History Started on Mainframes  Late 1960’s – early 1970’s  Help develop OS for the IBM 360 and follow-ons  Realized it could be used for “real-world” applications Became practical on PC’s in the last 5 years

Simple Example Debian Image CentOS Image VMdir PCnn (local PC)

Practical View of our use in 302 lab

Original Lab Setup AFS Class Directory (Read Only) install DebianCentOS Scratch PCnn (local PC)

Each VM  Only exists on the targeted PC Cannot write to the source AFS directory How to save?

Saving VMs Every lab machine you log onto has a “Home” directory That home directory is on the AFS server drive  Will follow you whatever machine in the lab you log onto Copy the VM to the Home directory and run?  Two problems: Sometimes the VM won’t work from an AFS Drive Changes to the VM are permanent

Saving VMs Solution:  Make a copy of your VMs (Debian and CentOS) to your Home AFS drive “One time” copy Put in aptly name directories:  myuseridDebian  myuseridCentOS Takes about 5 minutes to copy per OS  When doing a lab copy the OS of interest from the Home AFS directory to the scratch directory on the lab PC Takes about 5 minutes to copy down Depends on network load  If you want to save the new changed version copy the image back to the AFS server drive

Copying the VMs to local PC AFS “Home” DebianCentOS Scratch PCnn (local PC) DebianCentOS

When done testing on the local PC  Decide if you want to save the image  Yes Copy contents to home directory  No Do nothing or delete entry in /scratch

Saving the VMs from local PC AFS “Home” DebianCentOS Scratch PCnn (local PC) DebianCentOS

Home directory Space “Home” directory  On the desktop  a.k.a your userid Make a copy for each OS  Have about 8Gb available for your use on the AFS drive  About 2 OSs worth  The basic files:.vmx.vmdk  Rest contain history, changes, etc. Not required but should copy

Ground rules The PC’s /scratch directory is temporary  Don’t rely on it being around next time Directories in scratch may be deleted at any time  Only if space is needed Clean up after yourself  Get rid of any directory you are done with Remember to properly shut down VM before saving or logging off PC  May not save latest changes