1.1 Full Virtualization

a.k.a., emulation

• The host simulates everything down to and including the CPU level of the guest.
• The guest CPU can be different from that of the host.

These include the first virtualization systems (IBM 1966), often used to avoid/delay porting large application systems.

More modern instances:

• The Java Virtual Machine
• Game system emulators
• Parallels

1.2 Paravirtualization

a.k.a., OS-assisted virtualization, a.k.a., hypervisors

• CPU is not emulated, but OS is
  • Allows code between OS calls to run natively
• Many devices are simulated
• Guest CPU must be same as on host
• Guest OS can be different from that of host

Architectures:

• Hosted
• Hypervisor

1.2.1 Hosted Paravirtualization

a.k.a., type 2 hypervisor, client hypervisor

Runs the simulation as a host OS application.

• Examples:
  • VMWare
  • VirtualBox

1.2.2 Hypervisor Paravirtualization

a.k.a. type 1 hypervisor, bare metal hypervisor

The simulator is a “thin” OS sitting on top of the hardware.

• Examples
  • Xen
  • Hyper-V
  • VMWare

1.3 Containers

• Guest CPU is same as host’s
• Guest OS is same family as host’s
  • A thin OS simulation passes OS functions down to host.
• Applications are simulated

Instances:

• Docker
  • builds on OS support such as chroot
  • Oddly, docker hosted on Windows can virutalize wither Linux or Windows (but not both)