libvirt笔记（未完待续）

参考源地址：http://libvirt.org/formatdomain.html 

　　　　　　http://blog.csdn.net/qq250941970/article/details/6022094

libvirt是管理KVM的工具，通过libvirt可以管理配置虚拟机。而虚拟机的配置主要都是通过libvirt的xml文件来实现的，因此xml是十分重要的。

Domain XML format

从官网文档中，我们可以发现xml文件具有一定的格式。

1、Element and attribute overview（元素和属性概述）

根元素是所有虚拟机的域。它有两个属性，第一个属性是指定Hypervisor的类型，如”Xen”，“KVM”，“qemu”，“lxc”和“kqemu”。第二个属性是id，运行的guest Domain 的ID,已停用的guest Domain有没有ID值。

<domain type='xen' id='3'>
<name>xp</name>
<uuid>4dea22b31d52d8f32516782e98ab3fa0</uuid>
<description>Some human readable description</description>

2、Operating system booting（操作系统的启动）

BIOS bootloader 

 <os>
    <type>hvm</type>
    <loader readonly='yes' type='rom'>/usr/lib/xen/boot/hvmloader</loader>
    <nvram template='/usr/share/OVMF/OVMF_VARS.fd'>/var/lib/libvirt/nvram/guest_VARS.fd</nvram>
    <boot dev='hd'/>
    <boot dev='cdrom'/>
    <bootmenu enable='yes' timeout='3000'/>
    <smbios mode='sysinfo'/>
    <bios useserial='yes' rebootTimeout='0'/>
 </os>

  type 表示全虚拟化还是半虚拟化，hvm表示全虚拟化

  loader 全虚拟化才需要的，表示全虚拟化的守护进程所在位置

  boot 启动设备列表，如"fd"表示从文件启动, "hd"从硬盘启动, "cdrom"从光驱启动 和 "network"从网络启动，同时启动次序也可以由此顺序决定。

  bootmenu 当虚拟机启动时是否启用引导菜单，默认时表示使用引导菜单

Host bootloader

 半虚拟化的虚拟机启动一般使用这个，在主机使用一个伪引导来为guest Domain提供一个界面选择启动的内核。下面是个xen下半虚拟化的启动范例

<bootloader>/usr/bin/pygrub</bootloader>
 <bootloader_args>--append single</bootloader_args>

Bootloader给出主机操作系统引导程序的完整路径，运行这个引导程序，选择启动的内核，这个会因使用的Hypervisor不同而不同。

      bootloader_args该元素的可选bootloader_args允许命令行参数传递到bootloader

 Direct kernel boot（内核直接启动）

  <os>
    <type>hvm</type>
    <loader>/usr/lib/xen/boot/hvmloader</loader>
    <kernel>/root/f8-i386-vmlinuz</kernel>
    <initrd>/root/f8-i386-initrd</initrd>
    <cmdline>console=ttyS0 ks=http://example.com/f8-i386/os/</cmdline>
  </os>

3、CPU Allocation（cpu资源）

<domain>
  ...
  <vcpu placement='static' cpuset="1-4,^3,6" current="1">2</vcpu>
  ...
</domain>

所谓cpuset,就是在用户空间中操作cgroup文件系统来执行进程与cpu和进程与内存结点之间的绑定，在cpu调优中一般会用到（稍后再写）

4、基本资源

<memory>524288</memory>
  <currentMemory>524288</currentMemory>
  <memoryBacking>
    <hugepages/>
  </memoryBacking>
  <memtune>
    <hard_limit>1048576</hard_limit>
    <soft_limit>131072</soft_limit>
    <swap_hard_limit>2097152</swap_hard_limit>
    <min_guarantee>65536</min_guarantee>
  </memtune>
  <vcpu cpuset="1-4,^3,6" current="1">2</vcpu>

 <cpu match='exact'>
    <model>core2duo</model>
    <vendor>Intel</vendor>
    <topology sockets='1' cores='2' threads='1'/>
    <feature policy='disable' name='lahf_lm'/>
  </cpu>

这里可以看到各种资源的配置。内存大小、页面大小、memtune内存设定。cpu的model等等

5、 Lifecycle control（操作控制）

<on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>

用户请求不同动作时，对domain的执行也不同。

6、 Devices（外设）

 <devices>
    <disk type='file' snapshot='external'>
      <driver name="tap" type="aio" cache="default"/>
      <source file='/var/lib/xen/images/fv0' startupPolicy='optional'>
        <seclabel relabel='no'/>
      </source>
      <target dev='hda' bus='ide'/>
      <iotune>
        <total_bytes_sec>10000000</total_bytes_sec>
        <read_iops_sec>400000</read_iops_sec>
        <write_iops_sec>100000</write_iops_sec>
      </iotune>
      <boot order='2'/>
      <encryption type='...'>
        ...
      </encryption>
      <shareable/>
      <serial>
        ...
      </serial>
    </disk>
      ...
    <disk type='network'>
      <driver name="qemu" type="raw" io="threads" ioeventfd="on" event_idx="off"/>
      <source protocol="sheepdog" name="image_name">
        <host name="hostname" port="7000"/>
      </source>
      <target dev="hdb" bus="ide"/>
      <boot order='1'/>
      <transient/>
      <address type='drive' controller='0' bus='1' unit='0'/>
    </disk>
    <disk type='network'>
      <driver name="qemu" type="raw"/>
      <source protocol="rbd" name="image_name2">
        <host name="hostname" port="7000"/>
        <snapshot name="snapname"/>
        <config file="/path/to/file"/>
      </source>
      <target dev="hdc" bus="ide"/>
      <auth username='myuser'>
        <secret type='ceph' usage='mypassid'/>
      </auth>
    </disk>
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdd' bus='ide' tray='open'/>
      <readonly/>
    </disk>
    <disk type='network' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source protocol="http" name="url_path">
        <host name="hostname" port="80"/>
      </source>
      <target dev='hde' bus='ide' tray='open'/>
      <readonly/>
    </disk>
    <disk type='network' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source protocol="https" name="url_path">
        <host name="hostname" port="443"/>
      </source>
      <target dev='hdf' bus='ide' tray='open'/>
      <readonly/>
    </disk>
    <disk type='network' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source protocol="ftp" name="url_path">
        <host name="hostname" port="21"/>
      </source>
      <target dev='hdg' bus='ide' tray='open'/>
      <readonly/>
    </disk>
    <disk type='network' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source protocol="ftps" name="url_path">
        <host name="hostname" port="990"/>
      </source>
      <target dev='hdh' bus='ide' tray='open'/>
      <readonly/>
    </disk>
    <disk type='network' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source protocol="tftp" name="url_path">
        <host name="hostname" port="69"/>
      </source>
      <target dev='hdi' bus='ide' tray='open'/>
      <readonly/>
    </disk>
    <disk type='block' device='lun'>
      <driver name='qemu' type='raw'/>
      <source dev='/dev/sda'/>
      <target dev='sda' bus='scsi'/>
      <address type='drive' controller='0' bus='0' target='3' unit='0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw'/>
      <source dev='/dev/sda'/>
      <geometry cyls='16383' heads='16' secs='63' trans='lba'/>
      <blockio logical_block_size='512' physical_block_size='4096'/>
      <target dev='hdj' bus='ide'/>
    </disk>
    <disk type='volume' device='disk'>
      <driver name='qemu' type='raw'/>
      <source pool='blk-pool0' volume='blk-pool0-vol0'/>
      <target dev='hdk' bus='ide'/>
    </disk>
    <disk type='network' device='disk'>
      <driver name='qemu' type='raw'/>
      <source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/2'>
        <host name='example.com' port='3260'/>
      </source>
      <auth username='myuser'>
        <secret type='iscsi' usage='libvirtiscsi'/>
      </auth>
      <target dev='vda' bus='virtio'/>
    </disk>
    <disk type='network' device='lun'>
      <driver name='qemu' type='raw'/>
      <source protocol='iscsi' name='iqn.2013-07.com.example:iscsi-nopool/1'>
        <host name='example.com' port='3260'/>
      </source>
      <auth username='myuser'>
        <secret type='iscsi' usage='libvirtiscsi'/>
      </auth>
      <target dev='sdb' bus='scsi'/>
    </disk>
    <disk type='volume' device='disk'>
      <driver name='qemu' type='raw'/>
      <source pool='iscsi-pool' volume='unit:0:0:1' mode='host'/>
      <auth username='myuser'>
        <secret type='iscsi' usage='libvirtiscsi'/>
      </auth>
      <target dev='vdb' bus='virtio'/>
    </disk>
    <disk type='volume' device='disk'>
      <driver name='qemu' type='raw'/>
      <source pool='iscsi-pool' volume='unit:0:0:2' mode='direct'/>
      <auth username='myuser'>
        <secret type='iscsi' usage='libvirtiscsi'/>
      </auth>
      <target dev='vdc' bus='virtio'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/domain.qcow'/>
      <backingStore type='file'>
        <format type='qcow2'/>
        <source file='/var/lib/libvirt/images/snapshot.qcow'/>
        <backingStore type='block'>
          <format type='raw'/>
          <source dev='/dev/mapper/base'/>
          <backingStore/>
        </backingStore>
      </backingStore>
      <target dev='vdd' bus='virtio'/>
    </disk>
  </devices>

Encryption如果存在，指定如何给存储卷加密，查看存储加密页面更多信息

       Serial  这个在全虚拟化中比较重要，如果用文件存储，不加下面一段代码，虚拟机无法运行，下面代码是指出硬盘为串口

<serial type='pty'>

      <source path='/dev/pts/3'/>

      <target port='0'/>

 </serial>

<devices>
    <controller type='usb' index='0' model='ich9-ehci1'>
      <address type='pci' domain='0' bus='0' slot='4' function='7'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <master startport='0'/>
      <address type='pci' domain='0' bus='0' slot='4' function='0' multifunction='on'/>
    </controller>
    ...
  </devices>

USB设备的xml描述格式如上所示。

官网关于USB重定向的描述：

Redirected devices 

USB device redirection through a character device is supported since after 0.9.5 (KVM only):

<devices>
    <redirdev bus='usb' type='tcp'>
      <source mode='connect' host='localhost' service='4000'/>
      <boot order='1'/>
    </redirdev>
    <redirfilter>
      <usbdev class='0x08' vendor='0x1234' product='0xbeef' version='2.56' allow='yes'/> //0x08指大容量存储设备，文件系统。此处指只有大容量存储设备才能访问虚拟机
      <usbdev allow='no'/> //其他USB设备不行
    </redirfilter>
</devices>

USB常用设备类别和ID：

http://wenku.baidu.com/link?url=66ymV2VeFOTlFCAEVG2iU0yZ3TM5zzWOzs2ICDUNdfK_ZIbg0CKNxgVCS1j-UMfoWSzQ954WsPPx8tfl9vbJz-Tm8nbizgdLNvaEKoteItS

除此之外，还有网络设备，视频声卡