一、安装KVM

1.调整虚拟机

创建新的虚拟机；内存设置为4GB；勾选“虚拟化 Intel VT-x/EPT 或 AMD-V/RVI”选项；添加一块50G的新硬盘。

2.检查CPU参数

查看内存是否更改成功：

[root@kvm ~]# free
       total      used     free      shared    buff/cache   available
Mem:  1868688  125360  1582372     8752     160956     1584208
Swap:  097148     0     2097148

检查CPU虚拟化是否支持：
有vmx表示虚拟化开启成功

[root@kvm ~]# grep -Ei 'vmx|svm' /proc/cpuinfo
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon nopl xtopology tsc_reliable nonstop_tsc eagerfpu pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch arat tpr_shadow vnmi ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 invpcid mpx rdseed adx smap clflushopt xsaveopt xsavec xsaves
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon nopl xtopology tsc_reliable nonstop_tsc eagerfpu pni pclmulqdq vmx ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch arat tpr_shadow vnmi ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 invpcid mpx rdseed adx smap clflushopt xsaveopt xsavec xsaves

显示为空，则要查看虚拟机设置，是否打“√”

3.挂载新磁盘

检查硬盘是否新增成功：

[root@kvm ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk 
├─sda1            8:1    0  500M  0 part /boot
└─sda2            8:2    0 19.5G  0 part 
  ├─centos-root 253:0    0 17.5G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0   50G  0 disk 
sr0              11:0    1    4G  0 rom

成功新增了一块名为sdb的大小为50G的磁盘
格式化该磁盘为ext4格式：

[root@kvm ~]# mkfs.ext4 /dev/sdb 
mke2fs 1.42.9 (28-Dec-2013)
/dev/sdb is entire device, not just one partition!
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
3276800 inodes, 13107200 blocks
655360 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2162163712
400 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
4096000, 7962624, 11239424
Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done   
[root@kvm ~]# blkid /dev/sdb
//blkid+磁盘：查看磁盘信息
/dev/sdb: UUID="dab6d659-e334-41ed-a15a-96ce05b48c1a" TYPE="ext4"

格式化完成后，挂载磁盘，先创建挂载目录/kvm_data，然后进行挂载：

[root@kvm ~]# mkdir /kvm_data
[root@kvm ~]# mount /dev/sdb /kvm_data/

设置开机自动挂载：

[root@kvm ~]# vi /etc/fstab 
[root@kvm ~]# cat /etc/fstab 
#
# /etc/fstab
# Created by anaconda on Thu Aug 22 22:51:46 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos-root /                       xfs     defaults        0 0
UUID=34f3cd91-b7f0-44dd-9334-2bb66e939898 /boot                   xfs     defaults        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
/dev/sdb     /kvm_data           ext4      defaults    0 0

4.关闭防火墙和selinux

防火墙：

[root@kvm ~]# systemctl stop firewalld
[root@kvm ~]# systemctl disable firewalld
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
Removed symlink /etc/systemd/system/basic.target.wants/firewalld.service.

selinux：

[root@kvm ~]# vi /etc/selinux/config
[root@kvm ~]# cat /etc/selinux/config 
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=disabled           ##修改这一位置的内容
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected. 
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

修改完成后重启：

[root@kvm ~]# getenforce 
Disabled

5.安装KVM

安装KVM以及一些插件

[root@kvm ~]# yum install -y  virt-*  libvirt  bridge-utils qemu-img
 net——tools vim bash-c*
…………
Complete!

二、启动KVM

1.配置网卡

增加桥接网卡ifcfg-br0：

[root@kvm ~]# cd /etc/sysconfig/network-scripts/
[root@kvm network-scripts]# cp ifcfg-eno16777736 ifcfg-br0

修改桥接网卡br0的内容：

[root@kvm network-scripts]# vi ifcfg-br0 
[root@kvm network-scripts]# cat ifcfg-br0 
TYPE=Bridge
BOOTPROTO=none
NAME=br0
DEVICE=br0
ONBOOT=yes
IPADDR=192.168.200.20
NETMASK=255.255.255.0
GATEWAY=192.168.200.2
DNS1=114.114.114.114
DNS2=8.8.8.8

修改NAT网卡ifcfg-eno16777736：

[root@kvm network-scripts]# vi ifcfg-eno16777736
[root@kvm network-scripts]# cat ifcfg-eno16777736 
TYPE=Ethernet
BOOTPROTO=none
NAME=eno16777736
DEVICE=eno16777736
ONBOOT=yes
BRIDGE=br0

修改完网卡信息后，重启网卡服务并查看网卡信息：

[root@kvm network-scripts]# systemctl restart network
[root@kvm network-scripts]# service network restart
Restarting network (via systemctl):  [  OK  ]     
[root@kvm network-scripts]# ifconfig 
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.16.5  netmask 255.255.255.0  broadcast 
192.168.16.255
        inet6 fe80::20c:29ff:fe8d:1f90  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:8d:1f:90  txqueuelen 0  (Ethernet)
        RX packets 90  bytes 7092 (6.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 38  bytes 3604 (3.5 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  
mtu 1500
        ether 00:0c:29:8d:1f:90  txqueuelen 1000  (Ethernet)
        RX packets 126287  bytes 182444678 (173.9 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 32532  bytes 2953477 (2.8 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 0  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

可以看到br0网卡出现并带有IP，而以前的eno16777736网卡没有IP。网卡配置成功

2.启动libvirtdfuwu

首先检查KVM模块是否加载：

[root@kvm network-scripts]# lsmod|grep kvm
kvm_intel             162153  0 
kvm                   525259  1 kvm_intel

启动libvirtd并检查是否启动成功：

[root@kvm network-scripts]# systemctl start libvirtd
[root@kvm network-scripts]# ps -ef |grep libvirt
root      17270      1  1 04:36 ?        00:00:00 /usr/sbin/libvirtd
nobody    17383      1  0 04:36 ?        00:00:00 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/libexec/libvirt_leaseshelper
root      17384  17383  0 04:36 ?        00:00:00 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/libexec/libvirt_leaseshelper
root      17416   2264  0 04:36 pts/0    00:00:00 grep --color=auto libvirt

启动成功后，使用brctl命令可以看到两个网卡：

[root@kvm ~]# cd
[root@kvm ~]# brctl show
bridge name     bridge id               STP enabled     interfaces
br0            8000.000c298d1f90       no          eno16777736
virbr0          8000.525400c7e229       yes           virbr0-nic

3.命令行安装CentOS 7

通过Xftp上传Centos1511镜像到/tmp目录下，上传后使用ll命令查看/tmp目录下是否存在：

[root@kvm ~]# ll /tmp/
total 4228096
-rw-r--r--  1 root root 4329570304 Apr 15  2016 CentOS-7-x86_64-DVD-1511.iso

接下来使用virt-install进行CentOS 1511的安装：

[root@kvm ~]# yum install -y qemu-kvm
[root@kvm ~]# virt-install --name=test --memory=512,maxmemory=1024 --vcpus=1,maxvcpus=2 --os-type=linux --os-variant=rhel7 --location=/tmp/CentOS-7-x86_64-DVD-1511.iso --disk path=/kvm_data/test.img,size=10  --bridge=br0 --graphics=none --console=pty,target_type=serial  --extra-args="console=tty0 console=ttyS0"

—name：指定虚拟机的名称。
—memory：指定分配给虚拟机的内存资源大小。
maxmemory：指定可调节的最大内存资源大小，因为KVM支持热调整虚拟机的资源。
—vcpus：指定分配给虚拟机的CPU核心数量。
maxvcpus：指定可调节的最大CPU核心数量。
—os-type：指定虚拟机安装的操作系统类型。
—os-variant：指定系统的发行版本。
—location：指定ISO镜像文件所在的路径，支持使用网络资源路径，也就是说可以使用URL。
—disk path：指定虚拟硬盘所存放的路径及名称，size则是指定该硬盘的可用大小，单位是G。
—bridge：指定使用哪一个桥接网卡，也就是说使用桥接的网络模式。
—graphics：指定是否开启图形。
—console：定义终端的属性，target_type 则是定义终端的类型。
—extra-args：定义终端额外的参数。
等待一会儿就能看到以下界面：

Starting installer, one moment...
anaconda 21.48.22.56-1 for CentOS 7 started.
 * installation log files are stored in /tmp during the installation
 * shell is available on TTY2
 * when reporting a bug add logs from /tmp as separate text/plain attachments
17:01:51 Not asking for VNC because we don't have a network
================================================================================
================================================================================
Installation
 1) [x] Language settings                 2) [!] Timezone settings
        (English (United States))                (Timezone is not set.)
 3) [!] Installation source               4) [!] Software selection
        (Processing...)                          (Processing...)
 5) [!] Installation Destination          6) [x] Kdump
        (No disks selected)                      (Kdump is enabled)
 7) [ ] Network configuration             8) [!] Root password
        (Not connected)                          (Password is not set.)
 9) [!] User creation
        (No user will be created)
  Please make your choice from above ['q' to quit | 'b' to begin installation | 'r' to refresh]: 2
=====================================================================

“Timezone settings”时区设置选择 5) Asia亚洲，再选择城市 62) Shanghai上海，命令如下：

Timezone settings
Available regions
 1)  Africa                 6)  Atlantic              10)  Pacific
 2)  America                7)  Australia             11)  US
 3)  Antarctica             8)  Europe                12)  Etc
 4)  Arctic                 9)  Indian
 5)  Asia
Please select the timezone.
Use numbers or type names directly [b to region list, q to quit]: 5
================================================================================
================================================================================
Timezone settings
Available timezones in region Asia
 1)  Aden                  28)  Irkutsk               54)  Pyongyang
 2)  Almaty                29)  Jakarta               55)  Qatar
 3)  Amman                 30)  Jayapura              56)  Qyzylorda
 4)  Anadyr                31)  Jerusalem             57)  Rangoon
 5)  Aqtau                 32)  Kabul                 58)  Riyadh
 6)  Aqtobe                33)  Kamchatka             59)  Sakhalin
 7)  Ashgabat              34)  Karachi               60)  Samarkand
 8)  Baghdad               35)  Kathmandu             61)  Seoul
 9)  Bahrain               36)  Khandyga              62)  Shanghai
10)  Baku                  37)  Kolkata               63)  Singapore
11)  Bangkok             38)Krasnoyarsk             64) Srednekolymsk
12)  Beirut                39)  Kuala_Lumpur          65)  Taipei
13)  Bishkek               40)  Kuching               66)  Tashkent
14)  Brunei                41)  Kuwait                67)  Tbilisi
15)  Chita                 42)  Macau                 68)  Tehran
16)  Choibalsan            43)  Magadan               69)  Thimphu
17)  Colombo               44)  Makassar              70)  Tokyo
18)  Damascus             45)  Manila                71)  Ulaanbaatar
19)  Dhaka                 46)  Muscat                72)  Urumqi
20)  Dili                  47)  Nicosia               73)  Ust-Nera
21)  Dubai                 48)  Novokuznetsk          74)  Vientiane
22)  Dushanbe             49)  Novosibirsk           75)  Vladivostok
Press ENTER to continue
23)  Gaza                  50)  Omsk                  76)  Yakutsk
24)  Hebron             51)  Oral                  77)  Yekaterinburg
25)  Ho_Chi_Minh           52)  Phnom_Penh            78)  Yerevan
26)  Hong_Kong             53)  Pontianak
27)  Hovd
Please select the timezone.
Use numbers or type names directly [b to region list, q to quit]: 62
================================================================================

输入完毕后，可以发现2的[!]变成了[x]，证明配置完毕。
接下来我们配置“Software selection”，选择“4”，在选择“c”，因为默认就是minimalinstall，按Enter键：

Installation
 1) [x] Language settings                 2) [x] Timezone settings
        (English (United States))                (Asia/Shanghai timezone)
 3) [x] Installation source               4) [!] Software selection
        (Local media)                            (Minimal Install)
 5) [!] Installation Destination          6) [x] Kdump
        (No disks selected)                      (Kdump is enabled)
 7) [ ] Network configuration             8) [!] Root password
        (Not connected)                          (Password is not set.)
 9) [!] User creation
        (No user will be created)
  Please make your choice from above ['q' to quit | 'b' to begin installation |
  'r' to refresh]: 4
================================================================================
================================================================================
Base environment
Software selection
Base environment
 1)  [x] Minimal Install                 7)  [ ] Server with GUI
 2)  [ ] Compute Node                    8)  [ ] GNOME Desktop
 3)  [ ] Infrastructure Server           9)  [ ] KDE Plasma Workspaces
 4)  [ ] File and Print Server          10)  [ ] Development and Creative Work
 5)  [ ] Basic Web Server station
 6)  [ ] Virtualization Host
  Please make your choice from above ['q' to quit | 'c' to continue |
  'r' to refresh]: c

接下来我们配置“Installation Destination”，选择“5”，其余的依次选择“c”，按Enter键：

Installation
 1) [x] Language settings                 2) [x] Timezone settings
        (English (United States))           (Asia/Shanghai timezone)
 3) [!] Installation source               4) [!] Software selection
        (Processing...)                          (Processing...)
 5) [!] Installation Destination          6) [x] Kdump
        (No disks selected)                      (Kdump is enabled)
 7) [ ] Network configuration             8) [!] Root password
        (Not connected)                          (Password is not set.)
 9) [!] User creation
        (No user will be created)
 Please make your choice from above ['q' to quit | 'b' to begin installation |
 'r' to refresh]: 5
================================================================================
================================================================================
Probing storage...
Installation Destination
[x] 1) : 10 GiB (vda)
1 disk selected; 10 GiB capacity; 10 GiB free ...
  Please make your choice from above ['q' to quit | 'c' to continue |
  'r' to refresh]: c
================================================================================
================================================================================
Autopartitioning Options
[ ] 1) Replace Existing Linux system(s)
[x] 2) Use All Space
[ ] 3) Use Free Space
Installation requires partitioning of your hard drive. Select what space to use 
for the install target.
  Please make your choice from above ['q' to quit | 'c' to continue |
  'r' to refresh]: c
================================================================================
================================================================================
Partition Scheme Options
[ ] 1) Standard Partition
[ ] 2) Btrfs
[x] 3) LVM
[ ] 4) LVM Thin Provisioning
Select a partition scheme configuration.
  Please make your choice from above ['q' to quit | 'c' to continue |
  'r' to refresh]: c
Generating updated storage configuration
Checking storage configuration...
================================================================================
================================================================================
接下来配置“Root password”，选择8，按Enter键，命令如下：
Installation
 1) [x] Language settings                 2) [x] Timezone settings
        (English (United States))                (Asia/Shanghai timezone)
 3) [x] Installation source               4) [x] Software selection
        (Local media)                            (Minimal Install)
 5) [x] Installation Destination          6) [x] Kdump
        (Automatic partitioning selecte          (Kdump is enabled)
        d)                                8) [!] Root password
 7) [ ] Network configuration                    (Password is not set.)
        (Not connected)
 9) [!] User creation
        (No user will be created)
  Please make your choice from above ['q' to quit | 'b' to begin installation |
  'r' to refresh]: 8
================================================================================
================================================================================
Please select new root password. You will have to type it twice.

依次输入两次密码，密码相同，如123456：

Password: 123456 
//密码为密文，不显示。
Password (confirm): 123456
================================================================================
================================================================================
Question
You have provided a weak password: The password fails the dictionary check - it 
is too simplistic/systematic
Would you like to use it anyway?
//这句话的意思：你的密码太过简单，是否使用它，输入yes即可。
Please respond 'yes' or 'no': yes
=========================================================
=========================================================

配置完成按“b”，按Enter键后，开始安装：

Installation
 1) [x] Language settings                 2) [x] Timezone settings
        (English (United States))                (Asia/Shanghai timezone)
 3) [x] Installation source               4) [x] Software selection
        (Local media)                            (Minimal Install)
 5) [x] Installation Destination          6) [x] Kdump
        (Automatic partitioning selecte          (Kdump is enabled)
        d)                                8) [x] Root password
 7) [ ] Network configuration                    (Password is set.)
        (Not connected)
 9) [ ] User creation
        (No user will be created)
  Please make your choice from above ['q' to quit | 'b' to begin installation |
  'r' to refresh]: b
================================================================================
================================================================================
Progress
Setting up the installation environment
.
Creating disklabel on /dev/vda
.
Creating xfs on /dev/vda1
.
Creating lvmpv on /dev/vda2
.
Creating swap on /dev/mapper/centos-swap
.
……………………
Installing readline (34/297)
Installing gawk (35/297)
Installing elfutils-libelf (36/297)
Installing libgpg-error (37/297)
Installing libffi (38/297)
Installing libattr (39/297)
Installing libacl (40/297)
Installing libcap (41/297)
Installing libgcrypt (42/297)
Installing cpio (43/297)
Installing libxml2 (44/297)
Installing libnl3 (45/297)
Installing expat (46/297)
Installing p11-kit (47/297)
……………………
.
Performing post-installation setup tasks
.
Configuring installed system
.
Writing network configuration
.
Creating users
.
Configuring addons
.
Generating initramfs
.
Running post-installation scripts
.
        Use of this product is subject to the license agreement found at /usr/share/centos-release/EULA
        Installation complete.  Press return to quit 
//按回车
……………………
CentOS Linux 7 (Core)
Kernel 3.10.0-327.el7.x86_64 on an x86_64
localhost login: root
Password: 123456
[root@localhost ~]# 
//按“Ctrl+]”键，退出终端，回到宿主机。
[root@kvm ~]#

CentOS 1511安装完成

三、虚拟机管理

1.KVM基本管理

完成虚拟机安装，已经退回到宿主机，接下来我们来通过宿主机virsh命令进行管理刚才安装的CentOS 7虚拟机。
查看虚拟机列表：

[root@kvm ~]# virsh list
//查看虚拟机列表，只能看到正在运行的虚拟机
 Id    Name                           State
----------------------------------------------------
 2     test                           running
[root@kvm ~]# virsh list --all
//查看虚拟机列表，包括未运行的虚拟机
 Id    Name                           State
----------------------------------------------------
 2     test                           running

进入指定虚拟：

[root@kvm ~]# virsh console test
Connected to domain test
Escape character is ^]
//如果迟迟未动敲下回车就ok，下面就是正常登录时需要输入的用户名密码
CentOS Linux 7 (Core)
Kernel 3.10.0-327.el7.x86_64 on an x86_64
localhost login:

vrish常用命令：

virsh shutdown test 
//关闭虚拟机
virsh start test 
//开启虚拟机
virsh destroy test
//类似stop，这个是强制停止
virsh undefine test
//彻底销毁虚拟机，会删除虚拟机配置文件，virsh list --all就看不到
virsh autostart test
//宿主机开机该虚拟机也开机
virsh autostart --disable test
//解除开机启动
virsh suspend test
//挂起
virsh resume test
//恢复

2.克隆虚拟机

克隆虚拟机之前要先关闭虚拟机：

[root@kvm ~]# virsh shutdown test
Domain test is being shutdown
[root@kvm ~]# virt-clone  --original test --name test02 --file 
/kvm_data/test02.img
Allocating 'test02.img'                        3% 
[=                    ]  20 MB/s | 365 MB  00:08:23 ETA
//开始克隆
[root@kvm ~]# virt-clone  --original test --name test02 --file 
/kvm_data/test02.img
Allocating     'test02.img'         |  10 GB  00:00:35     
Clone 'test02' created successfully.
//克隆完成且成功

查看虚拟机配置文件/etc/libvirt/qemu，查看是否增加test02.xml文件：

[root@kvm ~]# ls /etc/libvirt/qemu/
networks  test02.xml  test.xml

接下来启动克隆的test02虚拟机，首先查看虚拟机列表，然后启动test02：

[root@kvm ~]# virsh list --all
 Id    Name                           State
----------------------------------------------------
 -     test                           shut off
 -     test02                         shut off
[root@kvm ~]# virsh start test02
Domain test02 started

3.快照管理

创建快照：

[root@kvm ~]# virsh snapshot-create test
Domain snapshot 1588485687 created

查看test.img信息，同时会查看到快照列表：

[root@kvm ~]# qemu-img info /kvm_data/test.img 
image: /kvm_data/test.img
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 1.1G
cluster_size: 65536
Snapshot list:
ID    TAG       VM SIZE   DATE              VM CLOCK
1     1588485687    0       2020-05-03 14:01:27   00:00:00.000
Format specific information:
    compat: 1.1
lazy refcounts: true

列出所有快照：

[root@kvm ~]# virsh snapshot-list test
 Name                 Creation Time             State
------------------------------------------------------------
 1588485687           2020-05-03 14:01:27 +0800 shutoff

查看当前快照版本：

[root@kvm ~]# virsh snapshot-current test
<domainsnapshot>
  <name>1588485687</name>
  <state>shutoff</state>
  <creationTime>1588485687</creationTime>
  <memory snapshot='no'/>
  <disks>
    <disk name='vda' snapshot='internal'/>
    <disk name='hda' snapshot='no'/>
  </disks>
  <domain type='kvm'>
    <name>test</name>
    <uuid>49d7cb9c-20dc-42dd-a260-01532b5132e5</uuid>
    <memory unit='KiB'>1048576</memory>
    <currentMemory unit='KiB'>524288</currentMemory>
    <vcpu placement='static' current='1'>2</vcpu>
    <os>
      <type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvm</type>
      <boot dev='hd'/>
    </os>
    <features>
      <acpi/>
      <apic/>
    </features>
    <cpu mode='custom' match='exact' check='partial'>
      <model fallback='allow'>Broadwell-noTSX-IBRS</model>
      <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>destroy</on_poweroff>
    <on_reboot>restart</on_reboot>
    <on_crash>destroy</on_crash>
    <pm>
      <suspend-to-mem enabled='no'/>
      <suspend-to-disk enabled='no'/>
    </pm>
    <devices>
      <emulator>/usr/libexec/qemu-kvm</emulator>
      <disk type='file' device='disk'>
        <driver name='qemu' type='qcow2'/>
        <source file='/kvm_data/test.img'/>
        <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='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>
      <controller type='pci' index='0' model='pci-root'/>
      <interface type='bridge'>
        <mac address='52:54:00:93:bf:07'/>
        <source bridge='br0'/>
        <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='mouse' bus='ps2'/>
      <input type='keyboard' bus='ps2'/>
      <memballoon model='virtio'>
        <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
      </memballoon>
      <rng model='virtio'>
        <backend model='random'>/dev/urandom</backend>
        <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
      </rng>
    </devices>
  </domain>
</domainsnapshot>

查看所有快照配置文件：

[root@kvm ~]# ls /var/lib/libvirt/qemu/snapshot/test/
1588485687.xml

恢复指定快照：

[root@kvm ~]# virsh snapshot-revert test 1588485687

删除指定快照：

[root@kvm ~]# virsh snapshot-delete test 1588485687
Domain snapshot 1588485687 deleted

4.磁盘格式化

查看虚拟磁盘格式：

[root@kvm ~]# qemu-img info /kvm_data/test.img
image: /kvm_data/test.img
file format: qcow2
virtual size: 10G (10737418240 bytes)
disk size: 1.1G
cluster_size: 65536
Format specific information:
    compat: 1.1
lazy refcounts: true

创建2GB的RAW格式磁盘：

[root@kvm ~]# qemu-img create -f raw /kvm_data/test_1.img 2G
Formatting '/kvm_data/test_1.img', fmt=raw size=2147483648

RAW格式的磁盘转换为qcow2格式：

[root@kvm ~]# qemu-img convert -O qcow2 /kvm_data/test_1.img /kvm_data/test_1.qcow2

查看test1.img大小：

[root@kvm ~]# ls -lh /kvm_data/test_1.img 
-rw-r--r-- 1 root root 2.0G May  3 15:11 /kvm_data/test_1.img
[root@kvm ~]# ls -lh /kvm_data/test_1.qcow2 
-rw-r--r-- 1 root root 193K May  3 15:38 /kvm_data/test_1.qcow2
##可以看到qcow2文件比较小，raw文件大小和我们指定空间大小一样是2G
##raw格式的磁盘性能比qcow2要好，但是raw格式的磁盘无法做快照

将test02转成raw格式：

[root@kvm ~]# qemu-img convert -O raw  /kvm_data/test02.img  /kvm_data/test02_2.raw

更改磁盘格式和文件路径，然后启动test02虚拟机：

[root@kvm ~]# virsh edit test02
…………
<disk type='file' device='disk'>
      <driver name='qemu' type='qcow'/>
      <source file='/kvm_data/test02.img'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</disk>
//找到上面这部分将qcow修改为raw，/kvm_data/test02.img改为/kvm_data/test02_2.raw
<disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/kvm_data/test02_2.raw'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</disk>
………………

查看磁盘所属用户和组：

[root@kvm ~]# ls -l /kvm_data/
total 3310628
drwx------ 2 root root       16384 Apr 29 00:20 lost+found
-rw-r--r-- 1 root root 10737418240 May  3 16:14 test02_2.raw
-rw------- 1 root root  1133772800 May  3 16:02 test02.img
-rw-r--r-- 1 root root  2147483648 May  3 15:11 test_1.img
-rw-r--r-- 1 root root      197120 May  3 16:05 test_1.qcow2
-rw------- 1 root root 10739384832 May  3 14:14 test.img

重启虚拟机test02，然后再次查看磁盘所属用户和组：

[root@kvm ~]# virsh start test02
Domain test02 started
[root@kvm ~]# ls -l /kvm_data/
total 3310628
drwx------ 2 root root       16384 Apr 29 00:20 lost+found
-rw-r--r-- 1 qemu qemu 10737418240 May  3 16:14 test02_2.raw
-rw------- 1 root root  1133772800 May  3 16:02 test02.img
-rw-r--r-- 1 root root  2147483648 May  3 15:11 test_1.img
-rw-r--r-- 1 root root      197120 May  3 16:05 test_1.qcow2
-rw------- 1 root root 10739384832 May  3 14:14 test.img
//启动后所属组变化成qemu的是test02_2.raw，证明这个磁盘正在被使用

5.磁盘扩容

在这里磁盘一共有两种格式，一种是RAW格式，一种是qcow2格式，接下来我们分别给这两种磁盘格式进行扩容。、
首先扩容RAW格式：

[root@kvm ~]# qemu-img resize /kvm_data/test02_2.raw +2G
Image resized.

查看test02_2.raw信息：

[root@kvm ~]# qemu-img info /kvm_data/test02_2.raw 
image: /kvm_data/test02_2.raw
file format: raw
virtual size: 12G (12884901888 bytes)
disk size: 1.0G

进入虚拟机test02，使用fdisk -l查看磁盘：

[root@kvm ~]# virsh console test02
[root@localhost ~]# fdisk -l
Disk /dev/vda: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0005b865
Device Boot      Start         End      Blocks   Id  System
/dev/vda1   *        2048     1026047      512000   83  Linux
/dev/vda2         1026048    20971519     9972736   8e  Linux LVM
Disk /dev/mapper/centos-root: 9093 MB, 9093251072 bytes, 17760256 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/centos-swap: 1073 MB, 1073741824 bytes, 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
//可以看到磁盘还是10 GB

退出终端，关闭test02虚拟机，重新启动，然后再次进入虚拟机test02，使用fdisk -l查看磁盘：

[root@kvm ~]# virsh destroy test02
Domain test02 destroyed
[root@kvm ~]# virsh start test02
Domain test02 started
[root@kvm ~]# virsh console test02
[root@localhost ~]# fdisk -l
Disk /dev/vda: 12.9 GB, 12884901888 bytes, 25165824 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0005b865
Device Boot       Start       End          Blocks   Id  System
/dev/vda1   *     2048       1026047      512000   83  Linux
/dev/vda2         1026048    20971519     9972736  8e  Linux LVM
Disk /dev/mapper/centos-root: 9093 MB, 9093251072 bytes, 17760256 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/centos-swap: 1073 MB, 1073741824 bytes, 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

可以看到已经变成12GB
接下来，对新增的2GB进行分区：

[root@localhost ~]# fdisk /dev/vda
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): n
//新建分区
Partition type:
   p   primary (2 primary, 0 extended, 2 free)
   e   extended
Select (default p): p
Partition number (3,4, default 3):
//按Enter键 
First sector (20971520-25165823, default 20971520): 
//按Enter键 
Using default value 20971520
Last sector, +sectors or +size{K,M,G} (20971520-25165823, default 25165823):
//按Enter键
Using default value 25165823
Partition 3 of type Linux and of size 2 GiB is set
Command (m for help): p
//查看分区列表
Disk /dev/vda: 12.9 GB, 12884901888 bytes, 25165824 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0005b865
Device Boot      Start       End          Blocks   Id  System
/dev/vda1   *    2048       1026047      512000   83  Linux
/dev/vda2        1026048    20971519     9972736  8e  Linux LVM
/dev/vda3        20971520   25165823     2097152  83  Linux
Command (m for help): w
//保存退出并退出终端

除了对已有磁盘扩容外，还可以额外增加磁盘：

[root@kvm ~]# qemu-img create -f raw /kvm_data/test02_3.raw 5G
Formatting '/kvm_data/test02_3.raw', fmt=raw size=5368709120

使用virsh edit编辑test02虚拟机，将新磁盘增加到test02虚拟机：

[root@kvm ~]# virsh edit test02
………………
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/kvm_data/test02_2.raw'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' 
function='0x0'/>
</disk>
//找到这一部分内容，在下面增加以下内容
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/kvm_data/test02_3.raw'/>
      <target dev='vdb' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09' 
function='0x0'/>
</disk>
………………

关闭test02虚拟机，重新启动，然后进入该虚拟机，使用fdisk -l查看磁盘

[root@kvm ~]# virsh destroy test02
Domain test02 destroyed
[root@kvm ~]# virsh start test02
Domain test02 started
[root@kvm ~]# virsh console test02
[root@localhost ~]# fdisk -l
Disk /dev/vda: 12.9 GB, 12884901888 bytes, 25165824 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0005b865
   Device Boot      Start      End         Blocks   Id  System
/dev/vda1   *        2048     1026047     512000   83  Linux
/dev/vda2         1026048    20971519     9972736   8e  Linux LVM
/dev/vda3        20971520    25165823     2097152   83  Linux
Disk /dev/vdb: 5368 MB, 5368709120 bytes, 10485760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/centos-root: 9093 MB, 9093251072 bytes, 17760256 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/centos-swap: 1073 MB, 1073741824 bytes, 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes