Preparing to install on a single node

• Prerequisites
• About OpenShift on a single node
• Requirements for installing OpenShift on a single node

Prerequisites

• You reviewed details about the OKD installation and update processes.

• You have read the documentation on selecting a cluster installation method and preparing it for users.

About OpenShift on a single node

You can create a single node cluster with standard installation methods. OKD on a single node is a specialized installation that requires the creation of a special ignition configuration ISO. The primary use case is for edge computing workloads, including intermittent connectivity, portable clouds, and 5G radio access networks (RAN) close to a base station. The major tradeoff with an installation on a single node is the lack of high availability.

Requirements for installing OpenShift on a single node

Installing OKD on a single node alleviates some of the requirements for high availability and large scale clusters. However, you must address the following requirements:

• Administration host: You must have a computer to prepare the ISO, to create the USB boot drive, and to monitor the installation.

• Production-grade server: Installing OKD on a single node requires a server with sufficient resources to run OKD services and a production workload.

  Table 1. Minimum resource requirements

  Profile	vCPU	Memory	Storage
  Minimum	8 vCPU cores	32GB of RAM	120GB

  One vCPU is equivalent to one physical core when simultaneous multithreading (SMT), or hyperthreading, is not enabled. When enabled, use the following formula to calculate the corresponding ratio: (threads per core × cores) × sockets = vCPUs

  The server must have a Baseboard Management Controller (BMC) when booting with virtual media.

• Networking: The server must have access to the internet or access to a local registry if it is not connected to a routable network. The server must have a DHCP reservation or a static IP address for the Kubernetes API, Ingress route, and cluster node domain names. You must configure the DNS to resolve the IP address to each of the following fully qualified domain names (FQDN):

  Table 2. Required DNS records

  Usage	FQDN	Description
  Kubernetes API	api.<cluster_name>.<base_domain>	Add a DNS A/AAAA or CNAME record. This record must be resolvable by clients external to the cluster.
  Internal API	api-int.<cluster_name>.<base_domain>	Add a DNS A/AAAA or CNAME record when creating the ISO manually. This record must be resolvable by nodes within the cluster.
  Ingress route	*.apps.<cluster_name>.<base_domain>	Add a wildcard DNS A/AAAA or CNAME record that targets the node. This record must be resolvable by clients external to the cluster.
  Cluster node	<hostname>.<cluster_name>.<base_domain>	Add a DNS A/AAAA or CNAME record and DNS PTR record to identify the node.

  Without persistent IP addresses, communications between the apiserver and etcd might fail.