There's more...

Configuring a virtual machine by writing the XML file, can be quite tedious and error-prone. An easier way of creating the VM from an existing image, or from an installation media (which can be physical, virtual, or a network location), is using the virt-install tool. Lets see an example of creating the same KVM instance using that tool.

1. We start by installing the package:

root@kvm:~# apt install virtinst
...
root@kvm:~#

1. Next, we define and start the new instance by invoking the virt-install command (if an instance with the same name already exist, you'll need to destroy and undefine it first):

root@kvm:~# virt-install --name kvm1 --ram 1024 --disk path=/tmp/debian.img,format=raw --graphics vnc,listen=146.20.141.158 --noautoconsole --hvm --import

Starting install...
Creating domain... | 0 B 00:00
Domain creation completed. You can restart your domain by running:
 virsh --connect qemu:///system start kvm1
root@kvm:~#

1. The new VM has now been defined and started. To confirm, execute:

root@kvm:~# virsh list --all
 Id Name State
----------------------------------------------------
 10 kvm1 running

root@kvm:~#

1. We can see the virtual machine definition file that was automatically generated by running the following code:

root@kvm:~# cat /etc/libvirt/qemu/kvm1.xml
<!--
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 kvm1
or other application using the libvirt API.
-->

<domain type='kvm'>
 <name>kvm1</name>
 <uuid>c3892cbf-812a-2448-7ad2-098ea8381066</uuid>
 <memory unit='KiB'>1048576</memory>
 <currentMemory unit='KiB'>1048576</currentMemory>
 <vcpu placement='static'>1</vcpu>
 <os>
   <type arch='x86_64' machine='pc-i440fx-trusty'>hvm</type>
    <boot dev='hd'/>
 </os>
 <features>
   <acpi/>
   <apic/>
   <pae/>
 </features>
 <clock offset='utc'/>
 <on_poweroff>destroy</on_poweroff>
 <on_reboot>restart</on_reboot>
 <on_crash>restart</on_crash>
 <devices>
   <emulator>/usr/bin/qemu-system-x86_64</emulator>
   <disk type='file' device='disk'>
     <driver name='qemu' type='raw'/>
     <source file='/tmp/debian.img'/>
     <target dev='hda' bus='ide'/>
     <address type='drive' controller='0' bus='0' target='0' unit='0'/>
   </disk>
   <controller type='usb' index='0'>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x01' 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>
   <interface type='network'>
     <mac address='52:54:00:59:e3:4e'/>
     <source network='default'/>
     <model type='rtl8139'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
   </interface>
   <serial type='pty'>
     <target port='0'/>
   </serial>
   <console type='pty'>
     <target type='serial' port='0'/>
   </console>
   <input type='mouse' bus='ps2'/>
   <input type='keyboard' bus='ps2'/>
   <graphics type='vnc' port='-1' autoport='yes' listen='146.20.141.158'>
     <listen type='address' address='146.20.141.158'/>
   </graphics>
   <video>
     <model type='cirrus' vram='9216' heads='1'/>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
   </video>
   <memballoon model='virtio'>
     <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
   </memballoon>
 </devices>
</domain>
root@kvm:~#