Supported installation methods

Full user-provisioned manual installation (UPI)

The manual UPI installation supports connected and disconnected environments. You can have your environment connected to the internet directly by using a proxy or disconnected by copying all artifacts that are required for an installation over to your local environment. The installer runs on your local environment and is CLI-based. Supported CLI options are Windows (x86), Linux (x86), Linux (s390x), and Mac.

You must create a YAML installation configuration file (install.yaml) as input and derive Ignition files (bootstrap.ign, master.ign, worker.ign) that are used when booting the different types of nodes of the cluster. You need to follow the procedure for bringing up the cluster nodes, which includes downloading the boot artifacts and booting up nodes. Although this installation option is still available and supported, manual UPI installation is no longer the recommended way to install Red Hat OpenShift. With the Assisted Installer and the Agent-Based Installer, more supportive models are available. Currently, only a manual installation supports the IBM Secure Execution based Red Hat OpenShift installation.

Assisted Installer

The Assisted Installer is a UI-based installer that leads you through the installation in an interactive web-based interface. This installer must be connected because it runs on the Red Hat Cloud Console and controls the installation from there. This means that your target cluster requires to communicate with the Red Hat Cloud Console.

The Assisted Installer collects the infrastructure information and creates the installation artifacts. Next, the discovery image, which can be an ISO or iPXE boot artifact, is generated. The discovery image is used to start each node in an initial discovered state and displays all available information about each node in the web interface. In the web interface, you can configure the nodes, including their roles. The installation can be started when the configuration of all nodes is complete.

The benefit of this process is that you need to work only with one single, simplified, and consolidated type of boot artifact that is provided by the service. The artifacts contain all required data including the Ignition files. Additionally, you do not need to manage the order of bringing up nodes during installation because orchestration is done by the Assisted Installer.

Agent-based Installer

The Agent-based Installer is a CLI-based installation that runs locally on your environment. The installation can be either connected and disconnected. The logic follows the same as the Assisted Installer, but the input is delivered by a YAML file for the infrastructure information and an install.yaml that specifies installation options. Based on this input, the Agent-based Installer outputs ISO and PXE boot files.

To install on the different environments on IBM Z and IBM LinuxONE, several options are supported to start a guest. The following list describes the boot artifact types:

ISO

An ISO file, also known as an ISO image, is a single file that contains an exact, uncompressed copy of an optical disk, like a CD, DVD, or Blu-ray. You can download the install program from the Red Hat Hybrid Cloud Console, it generates a bootable ISO image that contains the Assisted discovery agent and the Assisted Service. The ISO file is based on the input that you provide through the install-config.yaml and the agent-config.yaml. Currently, ISO boot is supported only for an installation with RHEL KVM. Since only one artifact is required, the installation process is simplified.

PXE

Preboot Execution Environment (PXE) is a client/server interface allowing computers in a network to be booted. Your guests have a simple network setup and pull the kernel.img, initrd.img, and generic.parm files from the server automatically over the network. However, for IBM Z and IBM LinuxONE, PXE boot artifacts are not used to boot over the network. They are required locally to boot the system in z/VM®, LPAR, and zCX environments. With RHEL KVM, you can also use PXE artifacts but ISO is preferred.

The basic idea is to push the artifacts to the correct place. For example, in z/VM push the artifacts to reader of the guests and then boot the guest from there. The same applies for the ISO artifact with RHEL KVM. If you download the installation program from the Red Hat Hybrid Cloud Console, then all installation artifacts are provided. If those artifacts are created by the Assisted- or Agent-Based Installer, the initrd.img is modified and contains the install artifacts.

Hosted Control Planes

The concept of Hosted Control Planes goes beyond the installation methods discussed previously.

Hosted Control Planes offer a consolidated, efficient, and secure approach to manage Red Hat OpenShift and other Kubernetes clusters at scale. Instead of running on dedicated infrastructure within each cluster, the control plane components are hosted on a separate management cluster as regular Red Hat OpenShift workloads.

Hosted Control Planes consist of pods that are launched on Red Hat OpenShift, which allows quick cluster creation, scale-up and scale-down. You can destroy a hosted cluster by consolidating the control nodes on a so-called hosting service cluster. Clusters created with Hosted Control Planes are divided into two parts: The control planes are nodes that are created as namespace per cluster on the hosting clusters and started as pods. The compute nodes that are added to the cluster are dedicated systems based on Red Hat CoreOS.

This approach allows to consolidate control nodes on the hosting clusters and saves resources. For IBM Z and IBM LinuxONE, the hosting cluster is currently supported on x86-based Red Hat OpenShift clusters only. The s390x-based compute nodes can be run on LPAR, z/VM, and RHEL KVM.