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VMs - PowerPoint PPT Presentation


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VMs. Virtual Machines. VM . What is a VM V irtual M achine Software implementation of a machine running on another machine The VM may or may not resemble the host machine E.g. Linux on a Windows machine Windows on Windows MVS on VM (IBM mainframe)

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slide1

VMs

Virtual Machines

slide2
VM
  • What is a VM
    • Virtual Machine
    • Software implementation of a machine running on another machine
      • The VM may or may not resemble the host machine
      • E.g.
        • Linux on a Windows machine
        • Windows on Windows
        • MVS on VM (IBM mainframe)
        • Linux (Intel Style) on MVS (IBM Mainframe)
why vms
Why VMs
  • Emulate software or hardware not available
    • Reduce costs
  • Reduce exposure
    • In a hostile environment
      • If machine becomes infected
      • Reboot (reload) VM
    • Test new environments
      • If mess up, just reboot (reload) VM
      • Isolate programs/environments
  • Adjust loads
    • Move/Start new VM’s to new/different servers as needed
vmware view of benefits
VMWare View of Benefits
  • Compatibility:
    • Virtual machines are compatible with all standard x86 computers
  • Isolation:
    • Virtual machines are isolated from each other as if physically separated
  • Encapsulation:
    • Virtual machines encapsulate a complete computing environment
  • Hardware independence:
    • Virtual machines run independently of underlying hardware
vm downside
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
vm brief history
VM Brief History
  • Started on Mainframes
    • Late 1960’s – early 1970’s
    • Help develop OS for the IBM 360 and followons
    • Realized it could be used for “real-world” applications
  • Became practical on PC’s in the last 10 years
vm types
VM Types
  • System virtual machines
    • Have an underlying physical machine
      • Runs one or more virtual machines
        • Each potentially running a different operating system
    • AKA hardware virtual machines
  • Hypervisor:
    • Software layer providing the virtualization
    • AKA - virtual machine monitor
  • Type 1 hypervisor
    • Runs on bare hardware
    • AKA - Native VM
  • Type 2 hypervisor
    • Runs on top of an operating system
    • AKA - Hosted VM
simple type 2 example

VM directory (/scratch)

Debian

Image

CentOS

Image

Simple Type 2 Example

PCnn (local workstation)

Debian Linux OS

original vm creation

/scratch

Debian

CentOS

install

Original VM Creation

NFS

“Common Directory”

(Read Only)

PCnn (local workstation)

each vm
Each VM
  • Each VM
    • Only exists on the targeted PC after installed
  • Cannot write back to the source NFS directory
    • Read only
  • How to save?
saving vms
Saving VMs
  • Every lab workstation you log onto has a network directory: network_storage
    • That network directory is located on the NFS server drive
    • That network directory will follow you to any machine in the lab you log onto
      • Actually follows the login ID
  • Copy the VM to the network directory and run?
    • Two problems:
      • Sometimes the VM won’t work properly from an NFS Drive
      • Changes to the VM are “permanent”
        • Make an error in the change  saved version now has the error
    • Bigger problem
      • VM dies when workstation removed from the lab network!
saving vms1
Saving VMs
  • Solution:
    • Make a copy of your VMs (Debian and CentOS) to your network NFS drive
      • “One time” copy
        • Backup copy
      • Put in aptly name directories:
        • myuseridDebian
        • myuseridCentOS
      • Takes about 3-6 minutes to copy per OS
        • Longer if there is a lot of network traffic
saving the vms on local pc to network file

/scratch

Debian

CentOS

Saving the VMs on local PC to network file

NFS

“network directory”

Debian

CentOS

PCnn (local workstation)

saving vms2
Saving VMs
  • “Restoring” VM to a workstation
    • Copy OS image of interest
      • From the network NFS directory
      • To the local /scratch directory
    • Takes about 5 minutes to copy down
      • Depends on network load
  • To save changes to the VM
    • Think carefully: do you want to save these changes?
    • Copy the image back to the NFS server drive
copying the vms to local pc

/scratch

Debian

CentOS

Copying the VMs to local PC

network directory

Debian

CentOS

PCnn (local workstation)

version management
Version management
  • When done testing a VM on the local PC
    • Decide if you want to save the image:
      • Yes
        • Copy contents back to network directory
      • No
        • Do nothing or delete entry in /scratch
usb drives
USB Drives
  • The same is true for USB drives to keep copies
  • Advantage:
    • Can take home with you
    • Not effected if home_directory disappears
  • Disadvantage
    • Can easily loose
    • May break
home directory space
Home directory Space
  • “Home” directory
    • On the desktop
    • On the local hard drive
    • a.k.a. your userid
  • Network Directory
    • on the NFS server
  • Make a copy for each OS to the Network Directory
    • Have about 12Gb available for your use on the NFS drive
    • About 2 OSs worth
    • The basic files:
      • .vmx
      • .vmdk
    • Rest contain history, changes, etc.
      • Not required but should copy
ground rules
Ground rules
  • The PC’s /scratch directory is temporary
    • Don’t rely on contents being available next time
  • Directories or data in /scratch may be deleted at any time
    • When 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
    • May corrupt images
sanity rules
Sanity Rules
  • NEVER run VM from network_storage directory
    • It will start
    • It will fail at the most critical time
    • It will corrupt your VM
  • Don’t run VM from USB device
    • It will start
    • It may fail
    • It may corrupt your VM
  • Start VM from its native directory
    • Sometimes the VMPlayer doesn’t make it clear where the image it is starting resides
  • Note: USB devices may be accessed by:
    • The workstation
    • A VM
    • BUT NOT BOTH at the same time!
      • If the VM uses it the workstation will loose access!
        •  the VM will die if you have started the VM from it!