命令行安装虚拟机，需要借助第一次用图形化安装的系统作为模板，来进行复制和修改。那么我们到底要复制什么？修改什么呢？因此我们必须先来了解一下虚拟机的组成。

一、虚拟机的组成部分

在这里我们以上一节图形化安装的centos7-01为例。

1、虚拟机配置文件

下面的xml文件就是我们的centos7-01虚拟机配置文件

[root@kvmserver kvmdata]# cd /etc/libvirt/qemu/
[root@kvmserver qemu]# ll
总用量 8
-rw-------  1 root root 4609 9月  17 13:44 centos7.0-01.xml
drwx------. 3 root root   42 5月  13 00:30 networks

2、虚拟机的磁盘镜像文件

上一节课说了因为我的宿主机安装时，var分区只有3G，所以我自定义的存储池，在根下的kvmdata目录内。我们看到的以.qcow2的文件就是centos7-01的磁盘镜像文件。

[root@kvmserver ~]# cd /kvmdata/
[root@kvmserver kvmdata]# ll
总用量 1633616
-rw------- 1 root root 21478375424 9月  17 14:55 centos7.0-01.qcow2

因此我们可以得出：

虚拟机的组成由：配置文件+磁盘镜像文件

那如果我们以centos7-01为模板，创建centos7-02，是不是修改这两个文件就可以呢？其实没必要两个都修改，我们只需要修改配置文件就可以了。磁盘镜像文件是无法修改的。要修改配置文件，就必须先了解配置文件的结构。

二、虚拟机配置文件

1、配置文件预览

以下代码中加有注释的，是可以改的，其他不需要修改

<!--
WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
OVERWRITTEN AND LOST. Changes to this xml configuration should be made using:
  virsh edit centos7.0-02
or other application using the libvirt API.
-->

<domain type='kvm'>
  <name>centos7.0-02</name>        #名字
  <uuid>784bcd3a-d59c-4f60-a52f-6674fc6ae33e</uuid>     #UID
  <memory unit='KiB'>1048576</memory>         #内存
  <currentMemory unit='KiB'>1048576</currentMemory>
  <vcpu placement='static'>1</vcpu>       #cpu数量
  <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</model>
  </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='/kvmdata/centos7.0-02.qcow2'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' 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='0x05' function='0x7'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci1'>
      <master startport='0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0' multifunction='on'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci2'>
      <master startport='2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x1'/>
    </controller>
    <controller type='usb' index='0' model='ich9-uhci3'>
      <master startport='4'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x2'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'/>
    <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='0x06' function='0x0'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:35:d5:3b'/>       #MAC码
      <source network='default'/>
      <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>
    <channel type='spicevmc'>
      <target type='virtio' name='com.redhat.spice.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='2'/>
    </channel>
    <input type='tablet' bus='usb'>
      <address type='usb' bus='0' port='1'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='spice' autoport='yes'>
      <listen type='address'/>
      <image compression='off'/>
    </graphics>
    <sound model='ich6'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </sound>
    <video>
      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1' primary='yes'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='2'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='3'/>
    </redirdev>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </memballoon>
    <rng model='virtio'>
      <backend model='random'>/dev/urandom</backend>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
    </rng>
  </devices>
</domain>

2、必须修改的地方

UID、name、MAC 这三个是必须要更改的。否则会冲突

3、可选修改的

cpu、内存