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Getting Started

A quick start guide to get KubeVirt up and running inside our container-based development cluster.

Note: Docker is used as default container runtime. If you want to use podman see PODMAN.md.

I just want it built and run it on my cluster

First, point the Makefile to the Docker registry of your choice:

export DOCKER_PREFIX=index.docker.io/myrepo
export DOCKER_TAG=mybuild

Then build the manifests and images:

make && make push && make manifests

Finally, push the manifests to your cluster:

kubectl create -f _out/manifests/release/kubevirt-operator.yaml
kubectl create -f _out/manifests/release/kubevirt-cr.yaml

Docker Desktop for Mac

The Bazel build system does not support the macOS keychain. Docker uses osxkeychain, which is the default credential helper for mac.

Modify the $HOME/.docker/config.json file to include the following snippet:

{
	"credHelpers": {
		"https://index.docker.io/v1/": ""
	}
}

This makes sure that no credential helpers are used for the specified registry and hence the credentials will be stored in the config.json file itself.

Now log in with docker login. You will get a warning message saying that no credential helper is configured. Your $HOME/.docker/config.json should look like:

{
	"auths": {
		"https://index.docker.io/v1/": {
			"auth": "XXXXXXXXXX"
		}
	},
	"credsStore": "desktop",
	"credHelpers": {
		"https://index.docker.io/v1/": ""
	}
}

Requirements

SELinux support

SELinux-enabled nodes need to have Container-selinux version 2.170.0 or newer installed.

Disabling the custom SELinux policy

By default, a custom SELinux policy gets installed by virt-handler on every node, and it gets used for VMIs that need it. Currently, the only VMIs using it are the ones that enable passt-based networking.
However, having KubeVirt install and use a custom SELinux policy is a security concern. It also increases virt-handler boot time 20/30 seconds.
Therefore, a feature gate was introduced to disable the installation and usage of that custom SELinux policy: DisableCustomSELinuxPolicy.
The side effect is that passt-enabled VMIs will fail to start, but only on nodes that use container-selinux version 2.192.0 or lower.
container-selinux releases 2.193.0 and newer include the necessary permissions for passt-enabled VMIs to run successfully.

Note: adding the DisableCustomSELinuxPolicy feature gate to an existing cluster will disable the use of the custom policy for new VMIs, but will not automatically uninstall the policy from the nodes. That can be done manually if needed, by running semodule -r virt_launcher on every node.

Building

The KubeVirt build system runs completely inside Docker. In order to build KubeVirt you need to have docker and rsync installed. You also need to have docker running, and have the permissions to access it.

Note: For running KubeVirt in the dockerized cluster, nested virtualization must be enabled - see here for instructions for Fedora. As an alternative software emulation can be allowed. Enabling nested virtualization should be preferred.

Dockerized environment

Runs master and nodes containers. Each one of them runs virtual machines via QEMU. In addition it runs dnsmasq and Docker registry containers.

Compatibility

The minimum compatible Kubernetes version is 1.15.0. Important features required for scheduling and memory are missing or incompatible with previous versions.

Compile and run it

To build all required artifacts and launch the dockerized environment, clone the KubeVirt repository, cd into it, and:

# Build and deploy KubeVirt on Kubernetes in our vms inside containers
# export KUBEVIRT_PROVIDER=k8s-1.20 #  uncomment to use a non-default KUBEVIRT_PROVIDER
make cluster-up
make cluster-sync

This will create a virtual machine called node01 which acts as node and control-plane. To create more nodes which will register themselves on control-plane, you can use the KUBEVIRT_NUM_NODES environment variable. This would create a control-plane and one node:

export KUBEVIRT_NUM_NODES=2 # schedulable control-plane + one additional node
make cluster-up

You can use the KUBEVIRT_MEMORY_SIZE environment variable to increase memory size per node. Normally you do not need it, because default node memory size is set.

export KUBEVIRT_MEMORY_SIZE=8192M # node has 8GB memory size
make cluster-up

Note: If you see the error below, check if the MTU of the container and the host are the same. If not, try to adjust them to be the same. See issue 2667 for more detailed info.

# ./cluster-up/kubectl.sh get pods --all-namespaces
NAMESPACE     NAME                                      READY   STATUS             RESTARTS   AGE
cdi           cdi-operator-5db567b486-grtk9             0/1     ImagePullBackOff   0          42m

Back-off pulling image "kubevirt/cdi-operator:v1.10.1"

To destroy the created cluster, type:

make cluster-down

Note: Whenever you type make cluster-down && make cluster-up, you will have a completely fresh cluster to play with.

Sync specific components

Note: The following is meant for allowing faster iteration on small changes to components that support it. Not every component is that simply exchangeable without a full re-deploy. Always test with the final SHA based method in the end.

In situations where you just want to work on a single component and rollout updates without re-deploying the whole environment, you can tell kubevirt to deploy using tags.

export KUBEVIRT_ONLY_USE_TAGS=true

After this any make cluster-sync will use the DOCKER_TAG for pulling images instead of SHAs. This means you can simply rebuild the component that changed and then kill the respective pods to cause a fresh pull:

PUSH_TARGETS='virt-api' ./hack/bazel-push-images.sh
kubectl delete po -n kubevirt -l kubevirt.io=virt-api

Once the respective component is back, it should be using your new build.

Accessing the containerized nodes via ssh

Based on the used cluster, node names might be different. You can get the names from following command:

# cluster-up/kubectl.sh get nodes
NAME     STATUS   ROLES                   AGE   VERSION
node01   Ready    control-plane,worker    13s   v1.18.3

Then you can execute the following command to access the node:

# ./cluster-up/ssh.sh node01
[vagrant@node01 ~]$

Automatic Code Generation

Some of the code in our source tree is auto-generated (see git ls-files|grep '^pkg/.*generated.*go$'). On certain occasions (but not when building git-cloned code), you need to regenerate it with:

make generate

Typical cases where code regeneration should be triggered are:

  • When changing APIs, REST paths or their comments (gets reflected in the API documentation, clients, generated cloners...)
  • When changing mocked interfaces (the mock generator needs to update the generated mocks)

We have a check in our CI system so that you do not miss when make generate needs to be called.

  • Another case is when kubevirtci is updated, in order to vendor cluster-up run hack/bump-kubevirtci.sh and then make generate

Testing

After a successful build you can run the unit tests:

    make
    make test

They do not need a running KubeVirt environment to succeed. To run the functional tests, make sure you have set up a dockerized environment. Then run

    make cluster-sync # synchronize with your code, if necessary
    make functest # run the functional tests against the dockerized VMs

If you would like to run specific functional tests only, you can leverage ginkgo command line options as follows (run a specified suite):

    FUNC_TEST_ARGS='-focus=vmi_networking_test -regexScansFilePath' make functest

In addition, if you want to run a specific test or tests you can prepend any Describe, Context and It statements of your test with an F and Ginkgo will only run items that are marked with the prefix. Remember to remove the prefix before issuing your pull request.

For additional information check out the Ginkgo focused specs documentation

Use

Congratulations, you are still with us and you have built KubeVirt.

Now it is time to get hands on and give it a try.

Create a first Virtual Machine

Finally start a VMI called vmi-ephemeral:

    # This can be done from your GIT repo, no need to log into a VMI

    # Create a VMI
    ./cluster-up/kubectl.sh create -f examples/vmi-ephemeral.yaml

    # Sure? Let's list all created VMIs
    ./cluster-up/kubectl.sh get vmis

    # Enough, let's get rid of it
    ./cluster-up/kubectl.sh delete -f examples/vmi-ephemeral.yaml


    # You can actually use kubelet.sh to introspect the cluster in general
    ./cluster-up/kubectl.sh get pods

    # To check the running kubevirt services you need to introspect the `kubevirt` namespace:
    ./cluster-up/kubectl.sh -n kubevirt get pods

This will start a VMI on control-plane or one of the running nodes with a macvtap and a tap networking device attached.

Example

$ ./cluster-up/kubectl.sh create -f examples/vmi-ephemeral.yaml
vm "vmi-ephemeral" created

$ ./cluster-up/kubectl.sh get pods
NAME                              READY     STATUS    RESTARTS   AGE
virt-launcher-vmi-ephemeral9q7es  1/1       Running   0          10s

$ ./cluster-up/kubectl.sh get vmis
NAME            AGE   PHASE     IP              NODENAME
vmi-ephemeral   11s   Running   10.244.140.77   node02

$ ./cluster-up/kubectl.sh get vmis -o json
{
    "kind": "List",
    "apiVersion": "v1",
    "metadata": {},
    "items": [
        {
            "apiVersion": "kubevirt.io/v1alpha2",
            "kind": "VirtualMachine",
            "metadata": {
                "creationTimestamp": "2016-12-09T17:54:52Z",
                "labels": {
                    "kubevirt.io/nodeName": "master"
                },
                "name": "vmi-ephemeral",
                "namespace": "default",
                "resourceVersion": "102534",
                "selfLink": "/apis/kubevirt.io/v1alpha2/namespaces/default/virtualmachineinstances/testvm",
                "uid": "7e89280a-be62-11e6-a69f-525400efd09f"
            },
            "spec": {
    ...

Accessing the Domain via VNC

First make sure you have remote-viewer installed. On Fedora run:

dnf install virt-viewer

Windows users can download remote-viewer from virt-manager.org, and may need to add virt-viewer installation folder to their PATH.

Then, after you made sure that the VMI vmi-ephemeral is running, type:

cluster-up/virtctl.sh vnc vmi-ephemeral

This will start a remote session with remote-viewer.

cluster-up/virtctl.sh is a wrapper around virtctl. virtctl brings all virtual machine specific commands with it and is a supplement to kubectl.

Note: If accessing your cluster through ssh, be sure to forward your X11 session in order to launch virtctl vnc.

Bazel and KubeVirt

Build.bazel merge conflicts

You may encounter merge conflicts in BUILD.bazel files when creating pull requests. Normally you can resolve these conflicts extremely easy by simply accepting the new upstream version of the files and run make again. That will update the build files with your changes.

Build.bazel build failures when switching branches

In case you work on two or more branches, make generate for example might fail, the reason is there is a Bazel server in the background, and when the base image changes, it should be auto restarted, the detection does not always work perfectly. To solve it, run docker stop kubevirt-bazel-server, which will stop the Bazel server.