Infrastructure software is the software that sits between a physical server and the apps that run on it: the virtualisation layer, the operating system and the container layer. A server is a powerful computer in a data centre that runs programs for many users over a network. Almost every company runs on this stack, even though most people never see it.
From the bottom up, there are three layers. The first is virtualisation. A program called a hypervisor splits one physical server into many virtual machines, each of which behaves like a separate computer. The second layer is the operating system inside each virtual machine, usually Linux. An operating system is the program that runs a computer and lets other programs use its processor, memory and disks. The third layer is the container layer. A container is a package that holds one piece of an app with everything it needs to run. Kubernetes decides which machine runs each container, and restarts any container that fails.
Consider a bank that runs its own data centre in Navi Mumbai and is launching a new personal loan app. Its infrastructure team builds the layers that the app will run on, one by one. They install 20 new servers. The hypervisor splits them into 300 virtual machines. Each virtual machine runs Linux from an enterprise Linux subscription. The loan app is written in Java, so each machine also runs a Java runtime, the program that runs Java code. The app's 40 services are packed into containers, and the bank's Kubernetes platform spreads them across the virtual machines. When a customer applies for a ₹3 lakh loan from her phone, her request passes through all these layers in a fraction of a second.
Some products combine or replace the bottom layers. Hyperconverged infrastructure joins ordinary servers into one system that does the computing, the storage and the virtualisation together. Private cloud software lets a company run its own servers the way a public cloud does: a team asks for a virtual machine on a web page and gets it in minutes. And with on-premises as a service, the machines sit in the company's own building, but the company pays for them by use, as it would in a cloud.
Almost all of this software is open source, which means anyone can download it and use it for free. So the companies that sell it do not sell the code. They sell what a bank needs before it trusts free software with its business: tested updates and security fixes, someone to call when a server fails at 2 a.m., and a promise that other major software and hardware will work with it. The page on the open source business model explains how this earns money.
One event changed this market recently. Broadcom bought VMware, the leading hypervisor company, in 2023. Many customers reported large price rises after the sale. So for the first time in about twenty years, many companies are choosing a hypervisor again.
A start-up that rents a virtual server from a cloud provider uses the same layers. The difference is that the provider runs the bottom ones for it.