Initialize VMs with startup scripts on OpenShift Virtualization Training

Introduction

Mon, 01 Jan 0001 00:00:00 +0000

When we create a virtual machine, we often want to configure the virtual machine to fit in our environment. To achieve this, OpenShift Virtualization supports the assignment of startup scripts which are executed automatically when the VM initializes. They are typically used to provide SSH keys, required configuration to run further configuration with ansible, deploy network configuration and so on.

These startup script methods are supported:

Cloud-init¹ and Ignition² which are targeting Linux and Unix systems
Sysprep³ to initialize Windows-based VMs

Cloud-init is the most-widely adopted method, and you will find great support on cloud providers such as AWS, GCP and Azure.

Cloud-init

Mon, 01 Jan 0001 00:00:00 +0000

In this section we will use cloud-init to initialize a Fedora Cloud¹ VM. Cloud-init is the de-facto standard for providing startup scripts to VMs.

Cloud-init is widely adopted. Some of the known users of cloud-init are:

Ubuntu
Arch Linux
CentOS
Red Hat
FreeBSD
Fedora
Gentoo Linux
openSUSE

Supported data sources

OpenShift Virtualization supports the cloudInitNoCloud and cloudInitConfigDrive data source methods.

Note

As it is the simplest data source you should stick to cloudInitNoCloud as the go-to data source. Only if cloudInitNoCloud is not supported by the cloud-init implementation you should switch to cloudInitConfigDrive. For example the implementation of coreos-cloudinit was known to require the cloudInitConfigDrive data source. However, as CoreOS has built Ignition this implementation is superseded but there may be more implementations.

`cloudInitNoCloud` data source

cloudInitNoCloud is a flexible data source to configure an instance locally. It can work without network access but can also fetch configuration from a remote server. The relevant configuration of a cloudInitNoCloud data source in a VM looks like this:

Ignition

Mon, 01 Jan 0001 00:00:00 +0000

In the previous section we created a VM using a cloud-init configuration Secret. This time we will do something similar but with Ignition and Linux Fedora CoreOS.

Known users of Ignition are:

Fedora CoreOS
Red Hat Enterprise Linux CoreOS
Flatcar
openSUSE MicroOS
SUSE Linux Enterprise Micro

Supported data sources

To provide Ignition data we have to use the cloudInitNoCloud data source.

`cloudInitNoCloud` data source

The relevant configuration of a cloudInitNoCloud data source in a VM looks like this:

Sysprep

Mon, 01 Jan 0001 00:00:00 +0000

This lab is not yet implemented. Please check the official documentation for additional information.

Initialize VMs with startup scripts on OpenShift Virtualization Training

Introduction

Cloud-init

Supported data sources

Note

cloudInitNoCloud data source

Ignition

Supported data sources

cloudInitNoCloud data source

Sysprep

`cloudInitNoCloud` data source

`cloudInitNoCloud` data source