This two-day test cloud servers stay pretty much, but knock yourself on ubuntu command after the completion of the deployment did not have a sense of accomplishment, and I do not know what's the use, so I wanted to think at this course in the end is what taught me, We know almost see the word, should not be called as the students themselves, but rather to himself as a developer, you do it far more results than you can only say what I will learn more valuable.
1. What is cloud server
Cloud server is to say, when you need computing services to you, when not needed, direct release, compared to direct physical server on the machine, in the cloud, more flexible.
2. What is virtualization technology
Virtualization technology to speak in plain English is the reality you want a computer that you can see the tangible live, but virtualization can help you take advantage of computer technology to some of the physical computer, such as CPU, memory, this fictional entity in the computer out of a virtual machine to use.
What is 3.KVM
KVM is a skill! A virtualization technology based on linux kernel!
Role is to make the kernel memory management, process management and direct management of virtual machines
It is said that we refer to the KVM KVM virtual machine , it is an open source system virtualization module, since Linux 2.6.20 is integrated in each major release of Linux.
Note: There is a KVM KVM switch , a computer management device, which can be achieved by a keyboard, mouse, control the display to multiple computers can be directly controlled by a computer of computer servers in different locations, and we are here talking about the KVM module are not the same as linux, pay attention!
KVM (Kernel-Based Virtual Machines) is based on a Linux kernel virtualization technology, can be directly converted to the Linux kernel Hypervisor (system management process
Sequence) so that the Linux kernel can manage virtual machines directly, direct calls to the Linux kernel memory management, process management subsystem to manage virtual machines
KVM is included into the Linux 2.6.20 version of the kernel in February 2007
There are two types of virtualization:
1: Hypervisor runs directly on the hardware (eg: kvm)
2: Hypervisor runs on the OS (e.g.: vmware)
Flower kvm technology is relatively long as the current system (Linux) loaded KVM module, Linux kernel directly into Hypervisor in, Hypervisor in the system can be run directly on the relevant
Management commands to create, delete ... KVM virtual machines, each virtual machine created out of there own user space and kernel space
Note execute various commands in the original system management module is not kvm
How cpu on that virtual machine is a virtual out?
The former is a thread some kernel, assisted by kvm module to complete, such as a cpu to run a virtual machine is a thread through the original kernel mode by kvm
Block auxiliary done in the kernel, two cpu is to use two threads, virtual cpu is a kernel thread from the original point of view
If the user space virtual machine kvm was i / o call, how is the process? (We know i / o calls are generally privileged instruction)
First user space, the system will initiate a call, the request is forwarded to your own kernel space and kernel space onward transmission to the original application qemu user-space simulated out each
Of hardware devices, and then transferred to the original kernel space qemu complete real i / o system call, if a non-privileged instruction i / o hardware to the type of cpu processed directly, so that this feature
kvm and technical performance losses compared to the real physical machine is less than 10%
kvm two types of components:
/ Dev / kvm: work on hypervisor, can be done in user space VM creation, launch and other management functions via ioctl (), system call; it is a character device
Function: Create a VM, the VM allocates memory, reading and writing VCPU registers, interrupt to inject VCPU, run VCPU etc.
qemu process: work in user space, primarily for analog IO device PC,
Can be understood as manage many computers, such as normal you need to manage different physical servers to one, but you can manage KVM is equivalent to all servers on a single machine, regardless of the geographical limitations of space.
What is 4.qemu
qemu simulator is a virtual operating system, saying that white is also software, is to mimic the physical components of a computer, allowing virtual memory, processor virtualization, etc.
5.kvm and qemu relationship
Responsibilities KVM module is open and initialize VMX function, provide the appropriate interface to support the operation of the virtual machine.
Analog KVM only CPU and memory, so a client (you build in a virtual machine centos ubuntu or the like) operating system can be up and running on the host (your physical machine), but you can not see it, and it can not communicate. As a result, the code was modified QEMU, he simulated CPU, memory code into KVM, and network cards, monitors and other keep, so QEMU + KVM became a complete virtualization platform.
Just KVM kernel module, users no law directly interact with the kernel module, users need to use the space management tool, and this tool is QEMU. KVM and QEMU complement each other, QEMU KVM achieved through hardware virtualization speeds, while KVM is used to simulate the device by QEMU. For KVM, the user space tools that not only matched only QEMU, there are other, such as RedHat development of libvirt, virsh, virt-manager, etc., is not the only option QEMU KVM's.
So simple and direct understanding is: QEMU is a computer simulator, and KVM provides acceleration for the computer simulation.
After learning of new knowledge should learn like this