1.1 Lesson 1

A Linux distribution is a bundle that consists of a Linux kernel and a selection of applications that are maintained by a company or user community. A distribution’s goal is to optimize the kernel and the applications that run on the operating system for a certain use case or user group. Distributions often include distribution-specific tools for software installation and system administration. This is why some distributions are mainly used for desktop environments where they need to be easy to use while others are mainly used to run on servers to use the available resources as efficiently as possible.

Another way to classify distributions is by referring to the distribution family they belong to. Distributions of the Debian distribution family use the package manager dpkg to manage the software that is run on the operating system. Packages that can be installed with the package manager are maintained by voluntary members of the distribution’s community. Maintainers use the deb package format to specify how the software is installed on the operating system and how it is configured by default. Just like a distribution, a package is a bundle of software and a corresponding configuration and documentation that makes it easier for the user to install, update and use the software.

The Debian GNU/Linux distribution is the biggest distribution of the Debian distribution family. The Debian GNU/Linux Project was launched by Ian Murdock in 1993. Today thousands of volunteers are working on the project. Debian GNU/Linux aims to provide a very reliable operating system. It also promotes Richard Stallman’s vision of an operating system that respects the freedoms of the user to run, study, distribute and improve the software. This is why it does not provide any proprietary software by default.

Ubuntu is another Debian-based distribution worth mentioning. Ubuntu was created by Mark Shuttleworth and his team in 2004, with the mission to bring an easy to use Linux desktop environment. Ubuntu’s mission is to provide a free software to everyone across the world as well as to cut the cost of professional services. The distribution has a scheduled release every six months with a long-term support release every 2 years.

Red Hat is a Linux distribution developed and maintained by the identically named software company, which was acquired by IBM in 2019. The Red Hat Linux distribution was started in 1994 and re-branded in 2003 to Red Hat Enterprise Linux, often abbreviated as RHEL. It is provided to companies as a reliable enterprise solution that is supported by Red Hat and comes with software that aims to ease the use of Linux in professional server environments. Some of its components require fee-based subscriptions or licenses. The CentOS project uses the freely available source code of Red Hat Enterprise Linux and compiles it to a distribution which is available completely free of charge, but in return does not come with commercial support.

Both RHEL and CentOS are optimized for use in server environments. The Fedora project was founded in 2003 and creates a Linux distribution which is aimed at desktop computers. Red Hat initiated and maintains the Fedora distribution ever since. Fedora is very progressive and adopts new technologies very quickly and is sometimes considered a test-bed for new technologies which later might be included in RHEL. All Red Hat based distributions use the package format rpm.

The company SUSE was founded in 1992 in Germany as a Unix service provider. The first version of SUSE Linux was released in 1994. Over the years SUSE Linux became mostly known for its YaST configuration tool. This tool allows administrators to install and configure software and hardware, set up servers and networks. Similar to RHEL, SUSE releases SUSE Linux Enterprise Server, which is their commercial edition. This is less frequently released and is suitable for enterprise and production deployment. It is distributed as a server as well as a desktop environment, with fit-for-purpose packages. In 2004, SUSE released the openSUSE project, which opened opportunities for developers and users to test and further develop the system. The openSUSE distribution is freely available to download.

Independent distributions have been released over the years. Some of them are based on either Red Hat or Ubuntu, some are designed to improve a specific propriety of a system or hardware. There are distributions built with specific functionalities like QubesOS, a very secure desktop environment, or Kali Linux, which provides an environment for exploiting software vulnerabilities, mainly used by penetration testers. Recently various super small Linux distributions are designed to specifically run in Linux containers, such as Docker. There are also distributions built specifically for components of embedded systems and even smart devices.

Embedded systems are a combination of computer hardware and software designed to have a specific function within a larger system. Usually they are part of other devices and help to control these devices. Embedded systems are found in automotive, medical and even military applications. Due to its wide variety of applications, a variety of operating systems based on the Linux kernel was developed in order to be used in embedded systems. A significant part of smart devices have a Linux kernel based operating system running on it.

Therefore, with embedded systems comes embedded software. The purpose of this software is to access the hardware and make it usable. The major advantages of Linux over any proprietary embedded software include cross vendor platform compatibility, development, support and no license fees. Two of the most popular embedded software projects are Android, that is mainly used on mobile phones across a variety of vendors and Raspbian, which is used mainly on Raspberry Pi.

The term cloud computing refers to a standardized way of consuming computing resources, either by buying them from a public cloud provider or by running a private cloud. As of 2017 reports, Linux runs 90% of the public cloud workload. Every cloud provider, from Amazon Web Services (AWS) to Google Cloud Platform (GCP), offers different forms of Linux. Even Microsoft offers Linux-based virtual machines in their Azure cloud today.

Linux is usually offered as part of Infrastructure as a Service (IaaS) offering. IaaS instances are virtual machines which are provisioned within minutes in the cloud. When starting an IaaS instance, an image is chosen which contains the data that is deployed to the new instance. Cloud providers offer various images containing ready to run installations of both popular Linux distributions as well as own versions of Linux. The cloud user chooses an image containing their preferred distribution and can access a cloud instance running this distribution shortly after. Most cloud providers add tools to their images to adjust the installation to a specific cloud instance. These tools can, for example, extend the file systems of the image to fit the actual hard disk of the virtual machine.