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2025-01-25 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Servers >
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What is QEMU?
QEMU is a generic and open source machine emulator and virtualizer QEMU official website
QEMU is a set of free software that simulates processors written by Fabrice Bellard developers. It is a complete software that can be run independently. Can independently simulate the whole computer (CPU/ memory / IO device) it is through a special "recompiler" to translate the binary code of a specific processor (CPU) to provide a series of hardware simulation, so that Guest OS thinks it is dealing with hardware directly (actually dealing with hardware simulated by QEMU). QEMU then translates these instructions to real hardware for operation, through which Guest OS can interact with various IO classes and USB devices on the host. However, because all its instructions need to be translated by QEMU, the performance will be relatively poor (stored in software simulation)
QEMU has two modes of operation:
System mode: the whole computer system can be simulated.
User mode: can run programs on other platforms that are different from the current hardware platform (such as running on x86 platform and running on ARM platform)
Code address: the latest version is 3.1. after 1.3, QEMU and QEMU-KVM are combined into one called QEUMU-KVM QEMU code.
What is KVM?
Red Hat's official website KVM knowledge points refer to Red Hat's official website.
The knowledge community of KVM refers to the KVM community.
KVM (Kernel-base-virtual machine) is actually a virtualization technology (kernel-level virtualization) provided in the Linux-like distribution kernel. The kernel can be directly used as Hypervisor and can be dynamically loaded independently in the kernel.
Note: its processor (CPU) itself must support virtualization extension
How it works:
KVM includes a kernel module, kvm.ko, which is used to implement core virtualization functions, and a module that is strongly related to the processor, kvm-intel.ko or kvm-amd.ko. KVM itself does not implement any simulation, but simply exposes a / dev/kvm interface. This interface can be used by the host to be responsible for creating vCPU, allocating address space of virtual memory, reading and writing vCPU registers and running vCPU. With KVM, the CPU instructions of Guest OS can be run directly without going through QEMU translation, which greatly improves the running speed. However, KVM's kvm.ko itself only provides the virtualization of CPU and memory, and the support of other networks and other IO needs to be supported by another component, QEMU-KVM.
Dynamic mount:
If the kernel of the kvm module immediately becomes a zombie and becomes a Hypervisor (quietly and erodes the Hypervisor on the parasitic kernel-level host), the user space becomes the management console of one of the virtual machines, completely parasitic and does not drive any driver hypervisor.
What is Hypervisor?
Generally speaking, Hypervisor is a technical implementation method that separates the operating system from the hardware abstraction. An intermediate software layer (either a software program or a firmware program) running between the physical server and the operating system
It allows multiple operating systems and applications to share a set of basic physical hardware, so it can also be regarded as a "meta" operating system in a virtual environment.
It can coordinate access to all physical devices and virtual machines on the server. When the server starts and executes Hypervisor, it allocates an appropriate amount of memory, CPU, network and disk to each virtual machine, and loads the guest operating system of all virtual machines. It enables these virtual machines to share the hardware resources of the physical server efficiently. Also known as virtual machine monitor VMM (Virtual Machine Monitor)
Hypervisor is the core of all virtualization technologies, and the ability to support multi-workload migration without interruption is the basic function of Hypervisor.
Hypervisor translates to Super Supervisor, which is extended to Super Supervisor, Super Multi-function Manager, Virtual Machine Manager, VMM.
Two types of Hypervisor (Host Virtualization)
Type 1 Virtualization: the host that runs on the hardware is not the host (directly runs the virtualization software and needs to drive the underlying hardware). Each host created is a virtual machine.
Type 2 Virtualization: install the operating system on the hardware (the operating system installs the virtual software vmware,virtualbox)
What is Libvirt?
Community site: libvirt community site
This is a user space virtual machine management tool developed by RedHat after it began to support KVM. The goal is to provide a single way to manage many different virtualization schemes and virtualized hosts, including KVM/QEMU,Xen,LXC,OpenVZ or VirtualBox hypervisors
Its Libvirt built-in API is widely used in the virtual machine monitor orchestration layer (Orchestration Layer) in cloud solution development. Commonly used management tools such as virsh,virt-install,virt-manager, etc.
Some of the main functions of Libvirt
VM management (virtual machine management)
Various virtual machine lifecycle operations, such as: start, stop, pause, save, restore and migrate, etc.; hot-swappable operations for many different types of devices, including disk, network interface, memory, CPU and other Remote machine support (support remote connection)
All the functions of Libvirt can be performed on machines running the libvirt daemon, including remote machines. With the simplest and no additional configuration of the SSH protocol, remote connections can support multiple network connection modes Storage management (storage management)
Any host running the libvirt daemon can be used to manage multiple types of storage: create multiple types of file images (qcow2,vmdk,raw,...), mount NFS shares, enumerate existing LVM volume groups, create new LVM volume groups and logical volumes, partition bare disk devices, mount iSCSI shares, and more. Network interface management (Network Interface Management)
Any host running the libvirt daemon can be used to manage physical and logical network interfaces, enumerate existing interfaces, configure (and create) interfaces, bridging, VLAN, port binding Virtual NAT and Route based networking (virtual NAT and route-based networks)
Any host running the libvirt daemon can manage and create a virtual network. The Libvirt virtual network implements a router using firewall rules to provide transparent access to the host network for virtual machines.
Installation: install libvirt and at least one virtual runtime environment (hypervisor)
Libvirt based on daemon / client architecture only needs to be installed on the machine that needs to be virtualized, and the service and client can be the same physical machine.
Libvirt KVM/QEMU driver KVM/QEMU driver site
Libvirt reference on Archlinux site?
Libvirt wiki referenc
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