KVM Virtual Machine XML Configuration Example

External

• https://libvirt.org/formatdomain.html

Internal

• Linux Virtualization Concepts

Example

<domain type='kvm'>
  <name>blue</name>
  <uuid>2a0523ba-9c44-47bd-8956-fc2b93ac1863</uuid>
  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
  <vcpu placement='static'>1</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'>
      <model fallback='allow'>Broadwell</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>restart</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='cdrom'>
          <driver name='qemu' type='raw'/>
          <source file='/iso-images/rhel-server-7.3-x86_64-dvd.iso'/>
          <target dev='hda' bus='ide'/>
          <readonly/>
          <address type='drive' controller='0' bus='0' target='0' unit='0'/>
      </disk>
      <disk type='file' device='disk'>
          <driver name='qemu' type='qcow2'/>
          <source file='/main-storage-pool/blue.qcow2'/>
          <target dev='vda' bus='virtio'/>
          <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
      </disk>
      <disk type='file' device='disk'>
          <driver name='qemu' type='raw'/>
          <source file='/main-storage-pool/blue-docker.raw'/>
          <target dev='vdb' bus='virtio'/>
          <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
      </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='0x04' function='0x0'/>
      </controller>
      <interface type='network'>
          <mac address='52:54:00:79:03:0c'/>
          <source network='default'/>
          <model type='virtio'/>
          <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>
      <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='tablet' bus='usb'>
          <address type='usb' bus='0' port='1'/>
      </input>
      <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>
  </devices>
</domain>

Elements

name

The short name of the virtual machine. Must consists of alphanumeric characters and it must be unique per virtualization host. Ideally, it should follow the virtual machine name convention when naming virtual machine. Also conventionally, it is also the name of the file storing the virtual machine image, with the ".img" prefix.

The guest ("domain") name may contain dot, so we can simulate a hierarchy ("ose36.master", or "environment-name.host-in-environment-name").

Example:

virsh list
Id    Name                           State
----------------------------------------------------
123   in                             running
124   appproxy                       running
151   support                        running
159   master1                        running
160   master2                        running
161   master3                        running
162   infranode1                     running
163   infranode2                     running
164   node1                          running
165   node2                          running

uuid

uuid is a globally unique identifier for the virtual machine. Must be in a RFC 4122-compliant format. Can be committed when defining a new machine. If omitted, a new UUID will be generated.

memory

memory represents the maximum amount of memory allocated to the guest at boot time. Valid units are "b" (bytes), "KB" (kilobytes - 1,000 bytes), "KiB" (kibibytes 1,024 bytes), "MB", "MiB", 'GB", "GiB", "TB", "TiB". However, the value will be rounded up to the nearest KiB by libvirt, and may be further rounded up to the granularity supported by the hypervisor. In case NUMA is configured for the guest, the memory element can be omitted.

currentMemory

currentMemory represents the actual allocation of memory for the guest. This value can be less than the maximum allocation, to allow for ballooning up the guests memory on the fly. If this is omitted, it defaults to the same value as the memory element. The unit attribute behaves the same as for memory.

maxMemory

See https://libvirt.org/formatdomain.html#elementsMemoryAllocation.

vcpu

https://libvirt.org/formatdomain.html#elementsCPUAllocation

vcpu defines the maximum number of virtual CPUs allocated. It must be between 1 and the maximum number supported by the hypervisor.

The placement attribute can be either "static" or "auto".

on_poweroff

destroy

It means that the virtual machine will be terminated completely and all resources released. It does NOT mean the definition will be removed, so the virtual machine can be started at a later time.

devices

The element of the <devices> container describe the devices provided to the guest.

disk

Any device that looks like a disk (hard drive, cdrom or paravirtualized driver) is specified via the disk element.

The type can be "file", "block", "dir", "network" or "volume".

The device attribute specifies how the disk should to be exposed to the guest OS. Possible values for this attribute are "disk", "cdrom", and "lun". The default value is "disk".

The <source> element defines where how the storage is maintained by the virtualization host. Possible values are file, block, dir, network and volume.

The <target> element controls the bus/device under which the disk is exposed to the guest OS. The dev attribute indicates the "logical" device name. The actual device name specified is not guaranteed to map to the device name in the guest OS, it is more of a device ordering hint.

The < driver> element specifies the guest driver managing the device.

interface

https://libvirt.org/formatdomain.html#elementsNICS

type

mac. The value for the "address" element can be randomly generated with the following script.

guest can be used to request a specific name for the network device on the guest:

 <interface type='network'>
   <source network='default'/>
   <guest dev='eth0'/>
   ...
 </interface>

Does not seem to be honored.