Virtualization Technologies

Guest Operating System virtualization
guest OS virtualization technologies include example vmware server and virtual Box

Shared kernel Virtualization

The kernel in simple terms handles all the interactions between the operating system and the physical h/w
The second key component is the root file system which contains all the libraris files and utilites necessary for the operation system to function
Shared kernel virtualization the virtual guest system Each have their own root file system but share the kernel of the host operating system
The ability of the kernel to dynamically change the current root file systems with out having to reboot the entire system
Guest Os must be compatible with the version of the kernel


Kernel level Virtualization
The host operating system runs on a specially modified kernel which contains extensions designed to manage and control multiple virtual machines.
Eg: User mode linux (UML), Kernel based virtual Machine(KVM)

Hypervisor virtualization
Range of protection levels also known as rings in which code can execute. Ring0 has the highest privileges and it is in the ring the the os kernel normally runs. Code executing in ring0 is said to be running in system space, kernel mode or supervisor mode. Application running on the operating system operates in less privileges rings typically ring 3.
The task of the operating system is to handle resources and memory allocation for the virtual machines. The hypervisor occupying ring 0 of the cpu the kernel for any guest os running on the system must run in less privileged cpu rings.


Paravirtualization
Replacing any privileged operations that will only run in ring0 of the cpu with calls to the hypervisor. The hypervisor in turn performs the task on behalf of the Guest kernel

Full Virtualization
The hypervisor provides cpu emulation to handle and modify privileges and protected cpu operations made by the unmodifed guest OS kernels. This emulation process requires both time and system resources.

hardware virtualization
Hardware virtualization leverage virtualization features built in to the latest generations of cpus's from both Intel VT and AMD-V provides extension necessary to run unmodified guest virtual machines without the over heads inherent in full virtualization cpu emulation. Provides additional privilege mode above ring0 in which the hypervisor can operate essentially

Virtualization Videos'

http://www.appzero.com/glossary
http://www.youtube.com/watch?v=p11lJOnALS4&feature=fvw
http://www.youtube.com/watch?v=oBlJqQ4oP1M
http://www.youtube.com/watch?v=48ZEvHYmul4&feature=related
http://www.youtube.com/watch?v=MnNX13yBzAU
http://www.youtube.com/watch?v=wRbYCnzj1x0&feature=related