QEMU-KVM虚拟化

以下命令行亲自执行有效，执行环境：

Compiled against library: libvirt 4.5.0
Using library: libvirt 4.5.0
Using API: QEMU 4.5.0
Running hypervisor: QEMU 1.5.3

虚拟化的分类

1. 服务器虚拟化：虚拟服务器
2. 桌面虚拟化：瘦客户机连接 win7 实现普通办公
3. 存储虚拟化：
   1. 　　SAN ( 基于磁盘 )
   2. 　　NAS ( NFS / Samba )
   3. 　　GlusterFS
4. 应用虚拟化：将办公软件虚拟化，最典型的就是 office
5. 网络虚拟化：SDN

Kernel-based Virtual Machine 的简称，是一个开源的系统虚拟化模块，自 Linux 2.6.20 之后集成在 Linux 的各个主要发行版本中。它使用 Linux 自身的调度器进行管理，所以相对于 Xen，其核心源码很少。KVM 目前已成为学术界的主流 VMM 之一。
KVM 的虚拟化需要硬件支持（如 Intel VT 技术或者 AMD V 技术)。是基于硬件的完全虚拟化。而 Xen 早期则是基于软件模拟的 Para-Virtualization，新版本则是基于硬件支持的完全虚拟化。但 Xen 本身有自己的进程调度器，存储管理模块等，所以代码较为庞大。广为流传的商业系统虚拟化软件 VMware ESX 系列是基于软件模拟的 Full-Virtualization。

hypervisor

Hypervisor——一种运行在基础物理服务器和操作系统之间的中间软件层,可允许多个操作系统和应用共享硬件。也可叫做VMM（ virtual machine monitor ），即虚拟机监视器。

Hypervisors是一种在虚拟环境中的“元”操作系统。他们可以访问服务器上包括磁盘和内存在内的所有物理设备。Hypervisors不但协调着这些硬件资源的访问，而且在各个虚拟机之间施加防护。当服务器启动并执行Hypervisor时，它会加载所有虚拟机客户端的操作系统同时会分配给每一台虚拟机适量的内存，CPU，网络和磁盘。

目前市场上各种x86 管理程序(hypervisor)的架构存在差异，三个最主要的架构类别包括：

• I型：虚拟机直接运行在系统硬件上，创建硬件全仿真实例，被称为“裸机”型。裸机型在虚拟化中Hypervisor直接管理调用硬件资源，不需要底层操作系统，也可以将Hypervisor看作一个很薄的操作系统。这种方案的性能处于主机虚拟化与操作系统虚拟化之间。

• II型：虚拟机运行在传统操作系统上，同样创建的是硬件全仿真实例，被称为“托管（宿主）”型。托管型/主机型Hypervisor运行在基础操作系统上，构建出一整套虚拟硬件平台（CPU/Memory/Storage/Adapter），使用者根据需要安装新的操作系统和应用软件，底层和上层的操作系统可以完全无关化，如Windows运行Linux操作系统。主机虚拟化中VM的应用程序调用硬件资源时需要经过:VM内核->Hypervisor->主机内核，因此相对来说，性能是三种虚拟化技术中最差的。
• Ⅲ型：虚拟机运行在传统操作系统上，创建一个独立的虚拟化实例（容器），指向底层托管操作系统，被称为“操作系统虚拟化”。操作系统虚拟化是在操作系统中模拟出运行应用程序的容器，所有虚拟机共享内核空间，性能最好，耗费资源最少。但是缺点是底层和上层必须使用同一种操作系统，如底层操作系统运行的是Windows系统，则VPS/VE就必须运行Windows。

 主要厂商及产品：VMware vSphere、微软Hyper-V、Citrix XenServer 、IBM PowerVM、Red Hat Enterprise Virtulization、Huawei FusionSphere、开源的KVM、Xen、VirtualBSD等。服务器虚拟化需要评估、选择和部署hypervisor，组织通常会选择一种主流的hypervisor：VMware的ESXi、微软的Hyper-V或者思杰的XenServer。然而，对很多组织来说，单独的hypervisor已经不能满足所有的虚拟化需求。这时候可以选择采用第二类hypervisor产品。随着服务器虚拟化技术的成熟，多hypervisor环境已经变得常见。

详见： https://www.jianshu.com/p/b9900b9dec34

全虚拟化

不需要对GuestOS操作系统软件的源代码做任何的修改，就可以运行在这样的VMM中

在全虚拟化的虚拟平台中，GuestOS并不知道自己是一台虚拟机，它会认为自己就是运行在计算机物理硬件设备上的HostOS。因为全虚拟化的VMM会将一个OS所能够操作的CPU、内存、外设等物理设备逻辑抽象成为虚拟CPU、虚拟内存、虚拟外设等虚拟设备后，再交由GuestOS来操作使用。这样的GuestOS会将底层硬件平台视为自己所有的，但是实际上，这些都是VMM为GuestOS制造了这种假象。

全虚拟化又分为：软件辅助的全虚拟化 & 硬件辅助的全虚拟化。

软件辅助全虚拟化架构图:

特权解除(优先级压缩)：从上述的软件辅助全虚拟化架构图中可以看出，VMM、GuestOS、GuestApplications都是运行在Ring 1-3用户态中的应用程序代码。当在GuestOS中执行系统内核的特权指令时，一般都会触发异常。这是因为用户态代码不能直接运行在核心态中，而且系统内核的特权指令大多都只能运行在Ring 0核心态中。在触发了异常之后，这些异常就会被VMM捕获，再由VMM将这些特权指令进行虚拟化成为只针对虚拟CPU起作用的虚拟特权指令。其本质就是使用若干能运行在用户态中的非特权指令来模拟出只针对GuestOS有效的虚拟特权指令，从而将特权指令的特权解除掉。

虚拟化在这里就遇到了一个难题，因为宿主操作系统是工作在ring0的，客户操作系统就不能也在ring0了，但是它不知道这一点，以前执行什么指令，现在还是执行什么指令，那肯定不行啊，没权限啊，玩不转啊。所以这时候虚拟机管理程序（VMM）就要避免这件事情发生。 （VMM在ring0上，一般以驱动程序的形式体现，驱动程序都是工作在ring0上，否则驱动不了设备） 
一般是这样做，客户操作系统执行特权指令时，会触发异常（CPU机制，没权限的指令，触发异常），然后VMM捕获这个异常，在异常里面做翻译，模拟，最后返回到客户操作系统内，客户操作系统认为自己的特权指令工作正常，继续运行。但是这个性能损耗，就非常的大，你想想原来，简单的一条指令，执行完，了事，现在却要通过复杂的异常处理过程。

这时候半虚拟化就来了，半虚拟化的思想就是，让客户操作系统知道自己是在虚拟机上跑的，工作在非ring0状态，那么它原先在物理机上执行的一些特权指令，就会修改成其他方式，这种方式是可以和VMM约定好的，这就相当于，我通过修改代码把操作系统移植到一种新的架构上来，就是定制化。所以像XEN这种半虚拟化技术，客户机操作系统都是有一个专门的定制内核版本，和x86、mips、arm这些内核版本等价。这样以来，就不会有捕获异常、翻译、模拟的过程了，性能损耗非常低。这就是XEN这种半虚拟化架构的优势。这也是为什么XEN只支持虚拟化Linux，无法虚拟化windows原因，微软不改代码啊。

半虚拟化 Paravirtualization

半虚拟化是需要GuestOS协助的虚拟化。因为在半虚拟化VVMM中运行的GuestOS，都需要将其内核源码进行都进过了特别的修改。半虚拟化VMM在处理敏感指令和内核态指令的流程上相对更简单一些。在半虚拟化VMM上运行的GuestOS都需要修改内核代码，主要是修改GuestOS指令集中的敏感指令和核心态指令。让HostOS在捕抓到没有经过半虚拟化VMM模拟和翻译处理的GuestOS内核态指令或敏感指令时，HostOS也能够准确的判断出该指令是否属于GuestOS(GuestOS知道自己是虚拟机)。这样就可以高效的避免了上述问题。典型的半虚拟化软件有——Xen、KVM-PowerPC(简易指令集).

可以后来，CPU厂商，开始支持虚拟化了，情况有发生变化，拿X86 CPU来说，引入了Intel-VT 技术，支持Intel-VT 的CPU，有VMX root operation 和 VMX non-root operation两种模式，两种模式都支持Ring 0 ~ Ring 3 这 4 个运行级别。这下好了，VMM可以运行在VMX root operation模式下，客户OS运行在VMX non-root operation模式下。也就说，硬件这层做了些区分，这样全虚拟化下，有些靠“捕获异常-翻译-模拟”的实现就不需要了。而且CPU厂商，支持虚拟化的力度越来越大，靠硬件辅助的全虚拟化技术的性能逐渐逼近半虚拟化，再加上全虚拟化不需要修改客户操作系统这一优势，全虚拟化技术应该是未来的发展趋势。

XEN是最典型的半虚拟化，不过现在XEN也支持硬件辅助的全虚拟化，大趋势，拗不过啊。。。 
KVM、VMARE这些一直都是全虚拟化。

硬件辅助虚拟化 HVM

005年 — Intel提出并开发了由CPU直接支持的虚拟化技术。这种虚拟化技术引入新的CPU运行模式和新的指令集，使得VMM和GuestOS运行于不同的模式下(VMM=Root Mode;GuestOS=Non-Root Mode)，GuestOS运行于受控模式，原来的一些敏感指令在受控模式下会全部陷入VMM，由VMM来实现模拟，这样就解决了部分非内核态敏感指令的陷入——模拟难题，而且模式切换时上下文的保存恢复由硬件来完成，这样就大大提高了陷入——模拟时上下文切换的效率 。该技术的引入使x86 CPU可以很容易地实现完全虚拟化。故皆被几乎所有之前分歧的各大流派所采用，包括KVM-x86，VMWare ESX Server 3，Xen 3.0 。

HVM的分类：
1). Intel –> VT-X
2). AMD –> AMD-V

内存虚拟化

原来的GuestOS使用的是虚拟内存，不可以缺少虚拟内存到物理内存的翻译，影响了虚拟机的效率。后来Intel EPT AMD RVI表示支持内存虚拟化。

内存虚拟化的映射实现

• A –> 虚拟地址(VA)，指GuestOS提供给其应用程序使用的线性地址空间。
• B –> 物理地址(PA)，经VMM抽象的，虚拟机看到的伪物理地址
• C –> 机器地址(MA)，真是的机器物理地址，即地址总线上出现的地址信号

内存地址的映射关系：：
GuestOS：PA = f(VA) #GuestOS维护着一套页表，负责VA到PA的映射
VMM：MA = g(PA) #VMM维护着一套页表，负责PA到MA的映射
通过转换方法实现了从虚拟地址到机器地址的映射。实际运行时，用户程序访问VA1，经过GuestOS的页表转换得到PA1，再由VMM介入并使用VMM的页表将PA1转换为MA1 。

总线虚拟化

分类：

• 1). Intel –> VT/d
• 2). AMD –> iommu

总线虚拟化可以实现将一块网卡分给若干个GuestOS使用，每个虚拟机1/N,性能高，接近真机。
从软件的角度出发，IO设备就是一堆状态寄存器，控制寄存器，中断并与其交互.

主要的虚拟化方式：设备接口完全模拟、前端-后端模拟（Xen） 
直接划分：直接把物理设备划分给Guest OS，无须经过VMM。Intel VT-d

内存虚拟化和总线虚拟化进一步的拉近了GuestOS和HostOS的运行性能。

安装KVM

安装步骤

　　确认 CPU 已经支持虚拟化，intel 的 CPU 虚拟化技术叫 vmx，AMD 的 CPU 叫 svm

grep -E   "vmx|svm" /proc/cpuinfo

　安装kvm-qemu平台及工具包

yum install qemu-kvm qemu-kvm-tools libvirt virt-manager virt-install

　　启动libvirtsd并设置为开机启动，librirtd会创建一个桥接的网卡virbr0而且IP地址是192.168.122.1

systemctl  start libvirtd &  systemctl  enable  libvirtd

　　查看网卡virbr0， ifconfig virbr0

• 

　　创建一个格式为raw大小为10G的裸磁盘

mkdir /data
qemu-img create -f raw /data/centos7.raw 10G
 成功后显示：Formatting '/data/centos7.raw', fmt=raw size=10737418240

　　使用本地 iso镜像进行安装

# 默认网络
virt-install --virt-type kvm --name centos7 --ram 1024 --cdrom=/home/CentOS-7-x86_64-Minimal-2003.iso --disk path=/data/centos7.raw --network network=default --graphics vnc,listen=0.0.0.0 --noautoconsole
# 桥接网络：
virt-install --virt-type kvm --name openstack-middleware1 --ram 4096 --vcpus 4 --cdrom=/usr/local/src/CentOS-7-x86_64-Minimal-1511.iso --disk path=/var/lib/libvirt/images/CentOS-7-x86_64-GenericCloud-1511-ok.qcow2 --network bridge=br0 --graphics vnc,listen=0.0.0.0 --noautoconsole

　　链接VNS

　　开始你的虚拟机中嵌套虚拟机的旅程吧。虚机安装过程略，过程中给内核传递 net.ifnames=0 以及 biosdevname=0 使网卡的命名为 eth*

　查看正在运行的虚拟机,查看virsh帮助

[root@hadoop001 ~]# virsh -help

virsh [options]... [>]
virsh [options]... > [args...]

  options:
    -c | --connect=URI      hypervisor connection URI
    -d | --debug=NUM        debug level [0-4]
    -e | --escape     set escape sequence for console
    -h | --help             this help
    -k | --keepalive-interval=NUM
                            keepalive interval in seconds, 0 for disable
    -K | --keepalive-count=NUM
                            number of possible missed keepalive messages
    -l | --log=FILE         output logging to file
    -q | --quiet            quiet mode
    -r | --readonly         connect readonly
    -t | --timing           print timing information
    -v                      short version
    -V                      long version
         --version[=TYPE]   version, TYPE is short or long (default short)
  commands (non interactive mode):

 Domain Management (help keyword 'domain')
    attach-device                  attach device from an XML file
    attach-disk                    attach disk device
    attach-interface               attach network interface
    autostart                      autostart a domain
    blkdeviotune                   Set or query a block device I/O tuning parameters.
    blkiotune                      Get or set blkio parameters
    blockcommit                    Start a block commit operation.
    blockcopy                      Start a block copy operation.
    blockjob                       Manage active block operations
    blockpull                      Populate a disk from its backing image.
    blockresize                    Resize block device of domain.
    change-media                   Change media of CD or floppy drive
    console                        connect to the guest console
    cpu-stats                      show domain cpu statistics
    create                         create a domain from an XML file
    define                         define (but don't start) a domain from an XML file
    desc                           show or set domain's description or title
    destroy                        destroy (stop) a domain
    detach-device                  detach device from an XML file
    detach-device-alias            detach device from an alias
    detach-disk                    detach disk device
    detach-interface               detach network interface
    domdisplay                     domain display connection URI
    domfsfreeze                    Freeze domain's mounted filesystems.
    domfsthaw                      Thaw domain's mounted filesystems.
    domfsinfo                      Get information of domain's mounted filesystems.
    domfstrim                      Invoke fstrim on domain's mounted filesystems.
    domhostname                    print the domain's hostname
    domid                          convert a domain name or UUID to domain id
    domif-setlink                  set link state of a virtual interface
    domiftune                      get/set parameters of a virtual interface
    domjobabort                    abort active domain job
    domjobinfo                     domain job information
    domname                        convert a domain id or UUID to domain name
    domrename                      rename a domain
    dompmsuspend                   suspend a domain gracefully using power management functions
    dompmwakeup                    wakeup a domain from pmsuspended state
    domuuid                        convert a domain name or id to domain UUID
    domxml-from-native             Convert native config to domain XML
    domxml-to-native               Convert domain XML to native config
    dump                           dump the core of a domain to a file for analysis
    dumpxml                        domain information in XML
    edit                           edit XML configuration for a domain
    event                          Domain Events
    inject-nmi                     Inject NMI to the guest
    iothreadinfo                   view domain IOThreads
    iothreadpin                    control domain IOThread affinity
    iothreadadd                    add an IOThread to the guest domain
    iothreaddel                    delete an IOThread from the guest domain
    send-key                       Send keycodes to the guest
    send-process-signal            Send signals to processes
    lxc-enter-namespace            LXC Guest Enter Namespace
    managedsave                    managed save of a domain state
    managedsave-remove             Remove managed save of a domain
    managedsave-edit               edit XML for a domain's managed save state file
    managedsave-dumpxml            Domain information of managed save state file in XML
    managedsave-define             redefine the XML for a domain's managed save state file
    memtune                        Get or set memory parameters
    perf                           Get or set perf event
    metadata                       show or set domain's custom XML metadata
    migrate                        migrate domain to another host
    migrate-setmaxdowntime         set maximum tolerable downtime
    migrate-getmaxdowntime         get maximum tolerable downtime
    migrate-compcache              get/set compression cache size
    migrate-setspeed               Set the maximum migration bandwidth
    migrate-getspeed               Get the maximum migration bandwidth
    migrate-postcopy               Switch running migration from pre-copy to post-copy
    numatune                       Get or set numa parameters
    qemu-attach                    QEMU Attach
    qemu-monitor-command           QEMU Monitor Command
    qemu-monitor-event             QEMU Monitor Events
    qemu-agent-command             QEMU Guest Agent Command
    reboot                         reboot a domain
    reset                          reset a domain
    restore                        restore a domain from a saved state in a file
    resume                         resume a domain
    save                           save a domain state to a file
    save-image-define              redefine the XML for a domain's saved state file
    save-image-dumpxml             saved state domain information in XML
    save-image-edit                edit XML for a domain's saved state file
    schedinfo                      show/set scheduler parameters
    screenshot                     take a screenshot of a current domain console and store it into a file
    set-lifecycle-action           change lifecycle actions
    set-user-password              set the user password inside the domain
    setmaxmem                      change maximum memory limit
    setmem                         change memory allocation
    setvcpus                       change number of virtual CPUs
    shutdown                       gracefully shutdown a domain
    start                          start a (previously defined) inactive domain
    suspend                        suspend a domain
    ttyconsole                     tty console
    undefine                       undefine a domain
    update-device                  update device from an XML file
    vcpucount                      domain vcpu counts
    vcpuinfo                       detailed domain vcpu information
    vcpupin                        control or query domain vcpu affinity
    emulatorpin                    control or query domain emulator affinity
    vncdisplay                     vnc display
    guestvcpus                     query or modify state of vcpu in the guest (via agent)
    setvcpu                        attach/detach vcpu or groups of threads
    domblkthreshold                set the threshold for block-threshold event for a given block device or it's backing chain element

 Domain Monitoring (help keyword 'monitor')
    domblkerror                    Show errors on block devices
    domblkinfo                     domain block device size information
    domblklist                     list all domain blocks
    domblkstat                     get device block stats for a domain
    domcontrol                     domain control interface state
    domif-getlink                  get link state of a virtual interface
    domifaddr                      Get network interfaces' addresses for a running domain
    domiflist                      list all domain virtual interfaces
    domifstat                      get network interface stats for a domain
    dominfo                        domain information
    dommemstat                     get memory statistics for a domain
    domstate                       domain state
    domstats                       get statistics about one or multiple domains
    domtime                        domain time
    list                           list domains

 Host and Hypervisor (help keyword 'host')
    allocpages                     Manipulate pages pool size
    capabilities                   capabilities
    cpu-baseline                   compute baseline CPU
    cpu-compare                    compare host CPU with a CPU described by an XML file
    cpu-models                     CPU models
    domcapabilities                domain capabilities
    freecell                       NUMA free memory
    freepages                      NUMA free pages
    hostname                       print the hypervisor hostname
    hypervisor-cpu-baseline        compute baseline CPU usable by a specific hypervisor
    hypervisor-cpu-compare         compare a CPU with the CPU created by a hypervisor on the host
    maxvcpus                       connection vcpu maximum
    node-memory-tune               Get or set node memory parameters
    nodecpumap                     node cpu map
    nodecpustats                   Prints cpu stats of the node.
    nodeinfo                       node information
    nodememstats                   Prints memory stats of the node.
    nodesuspend                    suspend the host node for a given time duration
    sysinfo                        print the hypervisor sysinfo
    uri                            print the hypervisor canonical URI
    version                        show version

 Interface (help keyword 'interface')
    iface-begin                    create a snapshot of current interfaces settings, which can be later committed (iface-commit) or restored (iface-rollback)
    iface-bridge                   create a bridge device and attach an existing network device to it
    iface-commit                   commit changes made since iface-begin and free restore point
    iface-define                   define an inactive persistent physical host interface or modify an existing persistent one from an XML file
    iface-destroy                  destroy a physical host interface (disable it / "if-down")
    iface-dumpxml                  interface information in XML
    iface-edit                     edit XML configuration for a physical host interface
    iface-list                     list physical host interfaces
    iface-mac                      convert an interface name to interface MAC address
    iface-name                     convert an interface MAC address to interface name
    iface-rollback                 rollback to previous saved configuration created via iface-begin
    iface-start                    start a physical host interface (enable it / "if-up")
    iface-unbridge                 undefine a bridge device after detaching its slave device
    iface-undefine                 undefine a physical host interface (remove it from configuration)

 Network Filter (help keyword 'filter')
    nwfilter-define                define or update a network filter from an XML file
    nwfilter-dumpxml               network filter information in XML
    nwfilter-edit                  edit XML configuration for a network filter
    nwfilter-list                  list network filters
    nwfilter-undefine              undefine a network filter
    nwfilter-binding-create        create a network filter binding from an XML file
    nwfilter-binding-delete        delete a network filter binding
    nwfilter-binding-dumpxml       network filter information in XML
    nwfilter-binding-list          list network filter bindings

 Networking (help keyword 'network')
    net-autostart                  autostart a network
    net-create                     create a network from an XML file
    net-define                     define an inactive persistent virtual network or modify an existing persistent one from an XML file
    net-destroy                    destroy (stop) a network
    net-dhcp-leases                print lease info for a given network
    net-dumpxml                    network information in XML
    net-edit                       edit XML configuration for a network
    net-event                      Network Events
    net-info                       network information
    net-list                       list networks
    net-name                       convert a network UUID to network name
    net-start                      start a (previously defined) inactive network
    net-undefine                   undefine a persistent network
    net-update                     update parts of an existing network's configuration
    net-uuid                       convert a network name to network UUID

 Node Device (help keyword 'nodedev')
    nodedev-create                 create a device defined by an XML file on the node
    nodedev-destroy                destroy (stop) a device on the node
    nodedev-detach                 detach node device from its device driver
    nodedev-dumpxml                node device details in XML
    nodedev-list                   enumerate devices on this host
    nodedev-reattach               reattach node device to its device driver
    nodedev-reset                  reset node device
    nodedev-event                  Node Device Events

 Secret (help keyword 'secret')
    secret-define                  define or modify a secret from an XML file
    secret-dumpxml                 secret attributes in XML
    secret-event                   Secret Events
    secret-get-value               Output a secret value
    secret-list                    list secrets
    secret-set-value               set a secret value
    secret-undefine                undefine a secret

 Snapshot (help keyword 'snapshot')
    snapshot-create                Create a snapshot from XML
    snapshot-create-as             Create a snapshot from a set of args
    snapshot-current               Get or set the current snapshot
    snapshot-delete                Delete a domain snapshot
    snapshot-dumpxml               Dump XML for a domain snapshot
    snapshot-edit                  edit XML for a snapshot
    snapshot-info                  snapshot information
    snapshot-list                  List snapshots for a domain
    snapshot-parent                Get the name of the parent of a snapshot
    snapshot-revert                Revert a domain to a snapshot

 Storage Pool (help keyword 'pool')
    find-storage-pool-sources-as   find potential storage pool sources
    find-storage-pool-sources      discover potential storage pool sources
    pool-autostart                 autostart a pool
    pool-build                     build a pool
    pool-create-as                 create a pool from a set of args
    pool-create                    create a pool from an XML file
    pool-define-as                 define a pool from a set of args
    pool-define                    define an inactive persistent storage pool or modify an existing persistent one from an XML file
    pool-delete                    delete a pool
    pool-destroy                   destroy (stop) a pool
    pool-dumpxml                   pool information in XML
    pool-edit                      edit XML configuration for a storage pool
    pool-info                      storage pool information
    pool-list                      list pools
    pool-name                      convert a pool UUID to pool name
    pool-refresh                   refresh a pool
    pool-start                     start a (previously defined) inactive pool
    pool-undefine                  undefine an inactive pool
    pool-uuid                      convert a pool name to pool UUID
    pool-event                     Storage Pool Events

 Storage Volume (help keyword 'volume')
    vol-clone                      clone a volume.
    vol-create-as                  create a volume from a set of args
    vol-create                     create a vol from an XML file
    vol-create-from                create a vol, using another volume as input
    vol-delete                     delete a vol
    vol-download                   download volume contents to a file
    vol-dumpxml                    vol information in XML
    vol-info                       storage vol information
    vol-key                        returns the volume key for a given volume name or path
    vol-list                       list vols
    vol-name                       returns the volume name for a given volume key or path
    vol-path                       returns the volume path for a given volume name or key
    vol-pool                       returns the storage pool for a given volume key or path
    vol-resize                     resize a vol
    vol-upload                     upload file contents to a volume
    vol-wipe                       wipe a vol

 Virsh itself (help keyword 'virsh')
    cd                             change the current directory
    echo                           echo arguments
    exit                           quit this interactive terminal
    help                           print help
    pwd                            print the current directory
    quit                           quit this interactive terminal
    connect                        (re)connect to hypervisor

View Code

# 当前正在运行的所有虚拟机：virsh list --all

# 命令帮助：virsh list --help
# 列出关闭的虚拟机：virsh list --inactive

  可以看到状态是关闭的。

　　启动虚拟机

virsh start centos7

　　关闭虚拟机

　　virsh shutdown centos7

　　查看配置文件：/etc/libvirt/qemu/这个目录下保存已经安装虚拟机的信息

　　　　　　查看centos7.xml

<domain type='kvm'>
  <name>centos7name>
  <uuid>6f0b80d9-4e1a-4d19-97d4-79459e5985d8uuid>
  <memory unit='KiB'>1048576memory>
  <currentMemory unit='KiB'>1048576currentMemory>
  <vcpu placement='static'>1vcpu>
  <os>
    <type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvmtype>
    <boot dev='hd'/>
  os>
  <features>
    <acpi/>
    <apic/>
  features>
  <cpu mode='custom' match='exact' check='partial'>
    <model fallback='allow'>Broadwell-noTSX-IBRSmodel>
    <feature policy='require' name='md-clear'/>
    <feature policy='require' name='spec-ctrl'/>
    <feature policy='require' name='ssbd'/>
  cpu>
  <clock offset='utc'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
  clock>
  <on_poweroff>destroyon_poweroff>
  <on_reboot>restarton_reboot>
  <on_crash>destroyon_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  pm>
  <devices>
    <emulator>/usr/libexec/qemu-kvmemulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/data/centos7.raw'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hda' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    disk>
    <controller type='usb' index='0' model='ich9-ehci1'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x7'/>
    controller>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <master startport='0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0' multifunction='on'/>
    controller>
    <controller type='usb' index='0' model='ich9-uhci2'>
      <master startport='2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x1'/>
    controller>
    <controller type='usb' index='0' model='ich9-uhci3'>
      <master startport='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x2'/>
    controller>
    <controller type='pci' index='0' model='pci-root'/>
    <controller type='ide' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    controller>
    <controller type='virtio-serial' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    controller>
    <interface type='network'>
      <mac address='52:54:00:93:61:2e'/>
      <source network='default'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    interface>
    <serial type='pty'>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      target>
    serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    console>
    <channel type='unix'>
      <target type='virtio' name='org.qemu.guest_agent.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    channel>
    <input type='tablet' bus='usb'>
      <address type='usb' bus='0' port='1'/>
    input>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'>
      <listen type='address' address='0.0.0.0'/>
    graphics>
    <video>
      <model type='cirrus' vram='16384' heads='1' primary='yes'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    video>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    memballoon>
    <rng model='virtio'>
      <backend model='random'>/dev/urandombackend>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    rng>
  devices>
domain>

　　备份虚拟机 

virsh dumpxml CentOS7 > CentOS7.xml.bak

　　删除一个虚拟机

virsh undefine centos7

　　从备份的 xml 文件中恢复

virsh define /root/CentOS7.xml.bak

到这里，一个完整的安装、删除、备份流程完成了，接下来开始进行CPU、内存、网络的配置。