Accessing a virtual machine by using its internal FQDN¶

You can access a virtual machine on a stable, fully qualified domain name (FQDN) by using headless services. A headless service creates DNS records for each pod instead of a virtual IP, enabling FQDN access without exposing specific ports.

Creating a headless service in a project by using the CLI¶

To create a headless service in a namespace, add the clusterIP: None parameter to the service YAML definition.

Prerequisites

• You have installed the OpenShift CLI (oc).

Procedure

1. Create a Service manifest to expose the VM, such as the following example:
   yaml

   apiVersion: v1
   kind: Service
   metadata:
     name: mysubdomain
   spec:
     selector:
       expose: me
     clusterIP: None
     ports:
     - protocol: TCP
       port: 1234
       targetPort: 1234

   • metadata.name defines the name of the service. This must match the spec.subdomain attribute in the VirtualMachine manifest file.
   • spec.selector defines the service selector that must match the expose:me label in the VirtualMachine manifest file.
   • spec.clusterIP defines a headless service.
   • spec.ports defines the list of ports that are exposed by the service. You must define at least one port. This can be any arbitrary value as it does not affect the headless service.
2. Save the Service manifest file.
3. Create the service by running the following command:
   terminal

   $ oc create -f headless_service.yaml

Mapping a virtual machine to a headless service by using the CLI¶

To connect to a virtual machine (VM) from within the cluster by using its internal fully qualified domain name (FQDN), you must first map the VM to a headless service. Set the spec.hostname and spec.subdomain parameters in the VM configuration file.

If a headless service exists with a name that matches the subdomain, a unique DNS A record is created for the VM in the form of <vm.spec.hostname>.<vm.spec.subdomain>.<vm.metadata.namespace>.svc.cluster.local.

Prerequisites

• You have installed the OpenShift CLI (oc).

Procedure

1. Edit the VirtualMachine manifest to add the service selector label and subdomain by running the following command:
   terminal

   $ oc edit vm <vm_name>

   Example VirtualMachine manifest file:

   yaml

   apiVersion: kubevirt.io/v1
   kind: VirtualMachine
   metadata:
     name: vm-fedora
   spec:
     template:
       metadata:
         labels:
           expose: me
       spec:
         hostname: "myvm"
         subdomain: "mysubdomain"
   # ...

   • spec.template.metadata.labels.expose defines a label that must match the spec.selector attribute of the Service manifest that you previously created.
   • spec.template.spec.hostname defines the hostname. If this attribute is not specified, the resulting DNS A record takes the form of <vm.metadata.name>.<vm.spec.subdomain>.<vm.metadata.namespace>.svc.cluster.local.
   • spec.template.spec.subdomain defines the subdomain. The spec.subdomain attribute must match the metadata.name value of the Service object.
2. Save your changes and exit the editor.
3. Restart the VM to apply the changes.

Connecting to a virtual machine by using its internal FQDN¶

You can connect to a virtual machine (VM) by using its internal fully qualified domain name (FQDN).

Prerequisites

• You have installed the virtctl tool.
• You have identified the internal FQDN of the VM from the web console or by mapping the VM to a headless service. The internal FQDN has the format <vm.spec.hostname>.<vm.spec.subdomain>.<vm.metadata.namespace>.svc.cluster.local.

Procedure

1. Connect to the VM console by entering the following command:
   terminal

   $ virtctl console vm-fedora

2. To connect to the VM by using the requested FQDN, run the following command:
   terminal

   $ ping myvm.mysubdomain.<namespace>.svc.cluster.local

   Example output:

   terminal

   PING myvm.mysubdomain.default.svc.cluster.local (10.244.0.57) 56(84) bytes of data.
   64 bytes from myvm.mysubdomain.default.svc.cluster.local (10.244.0.57): icmp_seq=1 ttl=64 time=0.029 ms

   In the preceding example, the DNS entry for myvm.mysubdomain.default.svc.cluster.local points to 10.244.0.57, which is the cluster IP address that is currently assigned to the VM.