管理KVM虚拟机
工具：libvirt
介绍：Libvirt 库是一种实现 Linux 虚拟化功能的 Linux® API，它支持各种虚拟机监控程序，包括 Xen 和 KVM，以及 QEMU 和用于其他操作系统的一些虚拟产品。
工作原理如下图
配置文件
KVM创建的虚拟机配置文件路径: /etc/libvirt/qemu，它是xml后缀文件，如之前我们创建的 CentOS-7-X86_64，它的配置文件是CentOS-7-X86_64.xml
备注：这个文件不能使用vi、vim命令进行修改，可以通过命令virsh edit CentOS-7-X86_64修改。
配置文件样例说明：
1 <domain type='kvm'> 2 <name>CentOS-7-X86_64</name> 名称 3 <uuid>ae53ced4-573c-4de0-9bd9-0852451b8573</uuid> 唯一 4 <memory unit='KiB'>2097152</memory> 内存 5 <currentMemory unit='KiB'>2097152</currentMemory> 当前内存 6 <vcpu placement='static'>1</vcpu> CPU 7 <os> 8 <type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvm</type> hvm表示硬件虚拟机 9 <boot dev='hd'/> 启动硬盘 10 </os> 11 <features> 12 <acpi/> 13 <apic/> 14 </features> 15 <cpu mode='custom' match='exact'> 16 <model fallback='allow'>Broadwell-noTSX</model> 17 </cpu> 18 <clock offset='utc'> 19 <timer name='rtc' tickpolicy='catchup'/> 20 <timer name='pit' tickpolicy='delay'/> 21 <timer name='hpet' present='no'/> 22 </clock> 23 <on_poweroff>destroy</on_poweroff> 24 <on_reboot>restart</on_reboot> 25 <on_crash>restart</on_crash> 26 <pm> 27 <suspend-to-mem enabled='no'/> 28 <suspend-to-disk enabled='no'/> 29 </pm> 30 <devices> 31 <emulator>/usr/libexec/qemu-kvm</emulator> 32 <disk type='file' device='disk'> 硬盘 33 <driver name='qemu' type='raw'/> 34 <source file='/opt/CentOS-7-x86_64.raw'/> 35 <target dev='vda' bus='virtio'/> 36 <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> 37 </disk> 38 <disk type='file' device='cdrom'> 39 <driver name='qemu' type='raw'/> 40 <target dev='hda' bus='ide'/> 41 <readonly/> 42 <address type='drive' controller='0' bus='0' target='0' unit='0'/> 43 </disk> 44 <controller type='usb' index='0' model='ich9-ehci1'> 45 <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x7'/> 46 </controller> 47 <controller type='usb' index='0' model='ich9-uhci1'> 48 <master startport='0'/> 49 <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/> 50 </controller> 51 <controller type='usb' index='0' model='ich9-uhci2'> 52 <master startport='2'/> 53 <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x1'/> 54 </controller> 55 <controller type='usb' index='0' model='ich9-uhci3'> 56 <master startport='4'/> 57 <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x2'/> 58 </controller> 59 <controller type='pci' index='0' model='pci-root'/> 60 <controller type='ide' index='0'> 61 <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> 62 </controller> 63 <controller type='virtio-serial' index='0'> 64 <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> 65 </controller> 66 <interface type='network'> 网络 67 <mac address='52:54:00:d0:dd:c9'/> 68 <source network='default'/> 69 <model type='virtio'/> 70 <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> 71 </interface> 72 <serial type='pty'> 73 <target port='0'/> 74 </serial> 75 <console type='pty'> 76 <target type='serial' port='0'/> 77 </console> 78 <channel type='unix'> 79 <target type='virtio' name='org.qemu.guest_agent.0'/> 80 <address type='virtio-serial' controller='0' bus='0' port='1'/> 81 </channel> 82 <input type='tablet' bus='usb'> 83 <address type='usb' bus='0' port='1'/> 84 </input> 85 <input type='mouse' bus='ps2'/> 86 <input type='keyboard' bus='ps2'/> 87 <graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0'> 88 <listen type='address' address='0.0.0.0'/> 89 </graphics> 90 <video> 91 <model type='cirrus' vram='16384' heads='1' primary='yes'/> 92 <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> 93 </video> 94 <memballoon model='virtio'> 95 <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/> 96 </memballoon> 97 </devices> 98 </domain>
重要命令
- 帮助命令
virsh --help
- dumpxml导出命令，将虚拟机配置文件导出做备份
virsh dumpxml CentOS-7-X86_64 > backup.xml
- 恢复备份，如果虚拟机通过undefine命令误删除，但是xml还存在，可以通过这个命令恢复
virsh define backup.xml
- 创建快照
virsh snapshot-create CentOS-7-X86_64
CPU动态扩容
centos 7上，kvm支持CPU动态扩容
1、在创建时需要设置maxcpus，如下图
2、对于已创建的虚拟机，修改它的xml文，例
virsh edit CentOS-7-X86_64
将 <vcpu placement='static'>1</vcpu>
修改成 <vcpu placement='auto' current='1'>4</vcpu>
表示动态VCPU，当前CPU为1，最大CPU为4
重启
virsh shutdown CentOS-7-X86_64 virsh start CentOS-7-X86_64
将虚拟机CPU改成2
virsh setvcpus CentOS-7-X86_64 2 --live
查看CPU个数，cat /proc/cpuinfo
查看CPU状态是否工作，cat /sys/devices/system/cpu/cpu1/online
内存动态扩容
修改内存为512
virsh qemu-monitor-command CentOS-7-X86_64 --hmp --cmd balloon 512
备注：内存最大值为创建时设置的值
查看虚拟机内存
virsh qemu-monitor-command CentOS-7-X86_64 --hmp --cmd info balloon
KVM磁盘
硬盘格式总体上分为两种：1为全镜像格式，2为稀疏格式
- 全镜像格式（典型代表raw格式）,其特点：设置多大就是多大，写入速度快，方便的转换为其他格式，性能最优，但是占用空间大，不支持快照
- 稀疏模式（典型代表qcow2格式），其特点：支持压缩，快照，镜像，更小的存储空间（即用多少占多少）
查看文件格式
qemu-img info CentOS-7-x86_64.raw
raw转化成qcow2
qemu-img convert -f raw -0 qcow2 /opt/CentOS-7-x86_64.raw /opt/test.qcow2
KVM网络
1、查看网络
brctl show
2、创建桥接网络
brctl addbr br0 brctl addbrif br0 eth0 ip addr del eth0 192.168.137.11/24 ifconfig br0 192.168.137.11/24 up route add default gw 192.168.137.2
virsh edit CentOS-7-X86_64
<interface type='network'>
<mac address='52:54:00:d0:dd:c9'/>
<source network='default'/>
<model type='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
改成
<interface type='bridge'>
<mac address='52:54:00:d0:dd:c9'/>
<source bridge='br0'/>
<model type='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
重启
virsh shutdown CentOS-7-X86_64 virsh start CentOS-7-X86_64
KVM优化
三方面：CPU、内存、IO
1、CPU优化
taskset --help 帮助命令
taskset -cp 0 pid
指定6573进程使用CPU0，减少cache miss
2、内存优化
- 开启大页内存
- 内存合并 cat /sys/kernel/mm/transparent_hugepage/enabled
3、IO优化
查看IO调度算法 cat /sys/block/sda/queue/scheduler，CentOS 7调度算法三种：noop、deadline、cfq
- noop 什么都不做，适用于SSD硬盘
- deadline “最后期限”算法
- cfq 完全公平队列
