Popular Linux distributions
Various Linux server distributions have gained quite a stable market share over the years. Corporate users usually standardize on one or two distributions depending on the business applications they use. Red Hat and SUSE are the two most famous enterprise Linux development companies and vendors and they both have similar offerings around the Linux operating system area. Nowadays, the third commercial Linux vendor, Canonical, is playing in the same category. Their Ubuntu Linux used to be best known as a developer workstation distribution, and it has quickly gained popularity as a production server operating system as well. Coupled with Canonical's commercial support offering, Ubuntu Linux is a great alternative to the two leading enterprise Linux distributions.
Red Hat was founded in 1993 when Bob Young and Marc Ewing joined forces and created Red Hat Software. In 1999, Red Hat went public on the New York Stock Exchange (NYSE). Before its acquisition by IBM in 2019, Red Hat had acquired dozens of small open-source companies, such as Cygnus (cross-platform tools), JBoss (Java middleware), Qumranet (the creators of KVM virtualization technology), Makara (a PaaS platform, the first version of OpenShift), ManageIQ (a hybrid cloud orchestrator, the first version of CloudForms), InkTank (the creators of Ceph storage technology), Ansible (a popular automation toolkit), and CoreOS (a small Linux distro for containers).
The complete acquisition list consists of more than 30 companies that most of you have probably not heard of, since the brands have been merged with Red Hat's other product lines. Red Hat Enterprise Linux (RHEL) is a very popular platform nowadays, especially for Java middleware JBoss products, as is the commercial Kubernetes packaging, OpenShift, since both are published by Red Hat as well.
SUSE was founded a year before Red Hat, in 1992, and became the first company to market Linux to enterprise customers. Rolard Dyroff, Burchard Steinbild, Hubert Mantel, and Thomas Fehr first named the company Gesellschaft für Software und Systementwicklung mbH and used the acronym SuSE, which came from the German phrase Software- und System-Entwicklung, meaning software and systems development. The first version of their product was an extension of the then-popular Slackware Linux distribution. In 1996, they released their first Linux distribution, based on the already-forgotten Linux distribution Jurix, and deviated from Slackware.
Over the years, SUSE has been acquired and changed names several times, most notably by Novell in 2003 and EQT Partners in 2018. SUSE itself acquired Hewlett Packard Enterprise's (HPE's) OpenStack and CloudFoundry assets in 2017, as well as Rancher Labs—a company known for its Kubernetes management platform—in 2020. Today, SUSE Linux Enterprise Server (SLES) is a very common platform for SAP system deployments.
For non-commercial use, it seems like Ubuntu is the clear winner if you look at the number of deployments. Ubuntu is based on Debian, once a very popular Linux distribution for server workloads.
CentOS, being fully compatible with RHEL, is also popular since it's typically used by RHEL professionals on their hobbyist projects and other work that doesn't have an enterprise-level budget available.
Over the years, there have been many popular Linux distributions for desktop use, but they have not gained popularity on server use cases. We will not be covering those in the scope of this book since Linux on Azure usually refers to using server operating systems.
In the next section, we will go into the details of using free and commercial Linux distributions on Azure, with a particular focus on RHEL, SLES, and Ubuntu Pro. However, most of the content is applicable to their free versions CentOS, openSUSE, and Ubuntu as well.