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
<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>
<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。
<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
