KVM虚拟化学习三——virt管理kvm虚拟机

1.libvirt相关知识

1. libvirt是一个虚拟化统一接口管理工具，openstack及很多虚拟化平台都采用libvirt来管理虚拟机

2. libvirt宕了，虚拟机仍然能运行，只是管理不了它了

3. 虚拟机配置是靠libvirt的xml文件来定义的，xml文件是自动生成的，不能手动编辑，只能通过virsh edit命令来编辑

• 虚拟机配置文件解析

[root@linux-node4 qemu]# virsh edit CentOS-7.2-x86_64    #编辑虚拟机配置
<domain type='kvm'>                                      #类型KVM
  <name>CentOS-7.2-x86_64</name>                         #虚拟机名称    
  <uuid>f7c3d6d4-c54e-4069-b76a-0a2c4253544a</uuid>      #默认生成的uuid
  <memory unit='KiB'>1048576</memory>                    #虚拟机设置的最大内存
  <currentMemory unit='KiB'>1048576</currentMemory>      #虚拟机当前内存
  <vcpu placement='static'>1</vcpu>                      #默认CPU为1
<os>
    <type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvm</type>        #hvm代表这是硬件虚拟机
    <boot dev='hd'/>                                     #启动设备为硬盘
 </os> 
<disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>                   #磁盘类型
      <source file='/opt/CentOS-7.2-x86_64.raw'/>        #磁盘位置
      <target dev='vda' bus='virtio'/>                   #磁盘名称vda,使用的virtio半虚拟化驱动
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </disk>
   <interface type='network'>                            #默认的是net网络
      <mac address='52:54:00:50:9e:0e'/>
      <source network='default'/>
      <model type='virtio'/>                             #模型
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>
 <memballoon model='virtio'>                             #内存扩展
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </memballoon>

2.virsh常用命令

[root@linux-node4 ~]# virsh list --all                  #列出虚拟机列表状态
 Id    Name                           State
----------------------------------------------------
 4     CentOS-7.2-x86_64              running
[root@linux-node4 ~]# virsh edit CentOS-7.2-x86_64      #编辑虚拟机配置文件
[root@linux-node4 ~]# virsh dumpxml CentOS-7.2-x86_64 > CentOS-7.2-x86_64.bak_$(date +%F).xml
#dumpxml : domain information in XML 导出虚拟机的配置
[root@linux-node4 ~]# ls
anaconda-ks.cfg  CentOS-7.2-x86_64.bak_2016-10-04.xml  ks-pre.log
[root@linux-node4 ~]# virsh define CentOS-7.2-x86_64.bak_2016-10-04.xml  #恢复虚拟机，但是如果连虚拟机硬盘也删了，那就回天乏术啦
[root@linux-node4 ~]# virsh start CentOS-7.2-x86_64     #启动虚拟机
[root@linux-node4 ~]# virsh shutdown CentOS-7.2-x86_64  #关闭虚拟机
[root@linux-node4 ~]# virsh reboot CentOS-7.2-x86_64    #重启虚拟机
[root@linux-node4 ~]# virsh undefine CentOS-7.2-x86_64  #删除虚拟机（慎用啊！赶快忘记这条命令吧，destroy(强行关机威力略差一点)）
[root@linux-node4 ~]# virsh suspend CentOS-7.2-x86_64   #挂起虚拟机
Domain CentOS-7.2-x86_64 suspended
[root@linux-node4 ~]# virsh resume CentOS-7.2-x86_64    #恢复虚拟机
Domain CentOS-7.2-x86_64 resumed

3.virsh快照管理

[root@linux-node4 ~]# virsh shutdown CentOS-7.2-x86_64    #要开启快照功能先关闭虚机，把镜像转为qcow2格式
Domain CentOS-7.2-x86_64 is being shutdown
[root@linux-node4 opt]# qemu-img convert -f raw CentOS-7.2-x86_64.raw -O qcow2 CentOS-7.2-x86_64.qcow2    #raw转为qcow2
[root@linux-node4 opt]# virsh edit CentOS-7.2-x86_64
  <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>                   #将磁盘格式从raw改为qcow2
      <source file='/opt/CentOS-7.2-x86_64.qcow2'/>        #改成qcow2镜像的路径
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </disk>

[root@linux-node4 ~]# virsh help snapshot        #快照帮助命令
 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    
[root@linux-node4 opt]# virsh snapshot-create-as CentOS-7.2-x86_64 snap1     #创建3个快照snap1,snap2,snap3
[root@linux-node4 snapshot]# virsh snapshot-create-as --domain CentOS-7.2-x86_64 --name snap2 --description "test kvm snap"
[root@linux-node4 snapshot]# virsh snapshot-create-as CentOS-7.2-x86_64 snap3    
[root@linux-node4 snapshot]# virsh snapshot-list CentOS-7.2-x86_64           #查看快照列表
 Name                 Creation Time             State
------------------------------------------------------------
 snap1                2016-10-05 09:26:15 +0800 running
 snap2                2016-10-05 09:39:05 +0800 running
 snap3                2016-10-05 09:57:00 +0800 running
[root@linux-node4 snapshot]# virsh snapshot-current CentOS-7.2-x86_64        #查看当前快照配置
[root@linux-node4 snapshot]# virsh snapshot-info CentOS-7.2-x86_64 snap1     #查看指定快照信息
Name:           snap1
Domain:         CentOS-7.2-x86_64
Current:        yes
State:          running
Location:       internal
Parent:         -
Children:       1
Descendants:    1
Metadata:       yes
#快照目录：/var/lib/libvirt/qemu/snapshot/
[root@linux-node4 qemu]# tree /var/lib/libvirt/qemu/snapshot/
/var/lib/libvirt/qemu/snapshot/
└── CentOS-7.2-x86_64
    ├── snap1.xml
    ├── snap2.xml
    └── snap3.xml
[root@linux-node4 ~]# virsh snapshot-revert CentOS-7.2-x86_64 snap1        #还原到快照1
[root@linux-node4 ~]# virsh snapshot-info CentOS-7.2-x86_64 snap1
Name:           snap1
Domain:         CentOS-7.2-x86_64
Current:        yes                                                        #状态为yes
State:          running
Location:       internal
Parent:         -
Children:       2
Descendants:    2
Metadata:       yes
[root@linux-node4 ~]# virsh snapshot-delete CentOS-7.2-x86_64 snap2        #删除快照2
Domain snapshot snap2 deleted
[root@linux-node4 ~]# virsh snapshot-list CentOS-7.2-x86_64
 Name                 Creation Time             State
------------------------------------------------------------
 snap1                2016-10-05 09:26:15 +0800 running
 snap3                2016-10-05 09:57:00 +0800 running

[root@linux-node4 ~]# virsh snapshot-delete CentOS-7.2-x86_64 snap1        #删除快照1
Domain snapshot snap1 deleted
[root@linux-node4 ~]# virsh snapshot-info CentOS-7.2-x86_64 snap1          #快照已经被删除
error: Domain snapshot not found: no domain snapshot with matching name 'snap1'

● 注意事项

     使用 qemu-img 创建快照、还原快照时，一定要在关机状态下，否则会搞崩虚拟机

参考：http://www.178linux.com/11256