Unix vs. Linux: a comparison of the two operating systems

Since the 1960s, Unix has been a major driving force in the development of digital infrastructures and has inspired numerous successors through its innovative techniques and programming. Similarly, Linux has become firmly established. In our in-depth comparison of ‘Unix vs. Linux’, we go over the similarities and differences between these popular operating systems.

What is Unix?

Unix is one of the oldest operating systems. Since its creation, it has been developed into a large operating system family with numerous versions. There are free open-source offshoots as well as proprietary versions, most of which have received an official license from the Open Group and require a fee. Nowadays, Unix is primarily installed on servers and powerful workstations. The following are the most important features of the operating system:

  • It was open source until the 1980s and then became proprietary.
  • There are open source offshoots available (e.g., FreeBSD).
  • It was one of the first operating systems to be based on the programming language C.
  • It is hardware and processor-independent (C-based Unix code is portable and can be flexibly adapted to any hardware environment).
  • It is capable of multitasking (multiple programs or processes can run simultaneously without a problem).
  • It is a multi-user system (multiple users can use the system at the same time and data, and resources can be restricted or authorised for access by other users as needed).
  • It is suitable for multiprocessor systems.
  • A central operating system kernel manages system activities and processes, and non-kernel software is kept in separate processes.
  • It uses a hierarchical file system which is standard today but was seen as innovative when it was introduced in 1980.
  • It is secure. Few malware programs target Unix, and it provides excellent permissions management, encryption technologies, and remote access via Secure Shell.
  • It is network-capable (integrated TCP/IP), has many network functions (e.g., Unix network tools), and provides a comprehensive range of services as a network server.
  • It has an extensive range of basic features (important development tools and libraries are integrated).
  • It uses professional programming designs and automation through sophisticated scripts.
  • It is known for its enhanced system stability (e.g., through memory protection).
  • It uses a standardised programming interface (POSIX).
Fact

The Portable Operating System Interface (POSIX) defines a standardized programming interface through which application software can interact with the Unix operating system. The IEEE and the Open Group are responsible for developing POSIX. The Single UNIX Specification is based on the POSIX. If a Unix operating system conforms to the Single UNIX Specification, it is allowed to use the Unix trademark (UNIX in all upper-case letters sometimes accompanied by the registered trademark symbol ®). There are Unix offshoots and derivatives that are fully POSIX compatible (e.g., AIX from IBM) or largely POSIX compatible (e.g., Linux).

Unix family (most important major versions)

Offshoots/derivatives

AT&T Unix derivative/System V version

AIX (IBM, certified as UNIX 98 and 03)

 

HP-UX (Hewlett Packard, certified as UNIX 95 and 03)

 

Oracle Solaris (Oracle, certified as UNIX 95, 98, 03 and V7)

BSD version

(BSD = Berkeley Software Distribution)

FreeBSD (range of distributions and derivatives available)

 

NetBSD (range of distributions and derivatives available)

 

OpenBSD (range of distributions and derivatives available)

What is Linux?

Linux is an operating system that is available online free of charge and is developed by an open source community that collaborates internationally. However, there are also closed source projects, mainly in the commercial sector. Like Unix, Linux has also spawned numerous offshoots (i.e. Linux distributions and derivatives that are spin-offs of Linux distributions) that extend the operating system kernel and turn it into a full-fledged operating system. Linux distributions are often developed with a specific application in mind, such as desktop systems or special operating systems for servers.

Linux is often equated with Unix or referred to as a Unix-like operating system owing in part to the fact that it was designed as a Unix-like system, that it contains Unix-like functions and that many Linux applications also run on Unix. However, Linux does not contain proprietary Unix code and is not currently verified by the Open Group as an official UNIX system.

The following are the key features of Linux:

  • It is open source.
  • open system development carried out by an international community of developers;
  • It is mostly free with a few paid commercial versions on the market.
  • Linux distributions extend the Linux kernel with practical application-oriented software.
  • It is suitable for multiprocessor systems.
  • multitasking (multiple programs can run simultaneously)
  • multi-user system
  • It supports many CPUs and hardware platforms (e.g., desktop computers, super and mainframe computers, servers).
  • It is suitable for mobile and small electronic devices (e.g., routers, smart home devices, the Internet of Things).
  • Linux is mostly written in C (C-based programs are easily portable between different operating and computer systems).
  • large selection of software and user interfaces
  • It has extensive security features (e.g., encryption techniques, sophisticated permissions and system management, Secure Shell for remote access).
  • sophisticated scripting (e.g., programming and automation through Shell scripts); and
  • standardised interfaces (POSIX, Linux Standard Base/LSB)
Fact

The Linux Standard Base (LSB) defines important standards (e.g., for binary interfaces, software libraries) to optimise compatibility between different Linux distributions.

Popular Linux distributions and derivatives

Special features

Debian

Distribution with a large software selection; supports 12 processor architectures

Ubuntu

A Debian derivative optimised for home computers

Linux Mint

A beginner-friendly Ubuntu offshoot; has a variety of desktop environments

Knoppix

The first popular live distribution (portable, no installation required); wide range of software; a Debian derivative

Gentoo

A source-based Linux distribution for advanced users; the system can be completely customised

Red Hat Enterprise Linux (RHEL)

A popular Linux server distribution for companies (currently the market leader in this area); extensive support from independent software manufacturers; requires a fee; part of the Fedora project

Fedora

The direct successor to Red Hat Linux (RHL); specialised in server and desktop systems; often used to replace RHL which is no longer in active development; also intended for beginners

openSUSE

An extensive Linux distribution, widely used mainly in Germany and the U.S.; uses the RPM package manager (free package management system); has its own configuration tool (YaST)

Unix vs. Linux: a comparison of these operating systems

History and development of Unix

When comparing Unix vs. Linux, you can confidently call Unix the IT dinosaur since the operating system (OS) was developed in its basic form back in the 60s by employees of Bell Labs (whose parent company was AT&T). After the source code of the original version from 1969 was published, many offshoots and successors were developed in the subsequent years. Due to this branching and disjointed development, there is no longer ‘the one single Unix’. Instead, there is a large Unix universe or family. Within the Unix family, two major versions have been leading the way for many years now: BSD and System V.

The Berkeley Software Distribution (BSD) was created in 1977 as a variant of the Unix operating system at the University of California, Berkeley. Over time, a more extensive family of Unix derivatives was developed from the original version. The most well-known of these include the distributions FreeBSD, OpenBSD and NetBSD, which in turn gave rise to additional BSD projects. Unix software under a BSD license can be used freely. However, FreeBSD no longer contains original Unix code from the AT&T version due to licensing issues.

The System V family is the second major development branch. It has produced, among others, the UNIX systems from IBM (AIX), Hewlett Packard (HP-UX) and Oracle (Oracle Solaris) which are still commercially relevant today. When it was launched in 1983, System V initially referred to a very specific Unix derivative. Since then, however, it has come to refer to an entire family or class of Unix derivatives that are directly derived from the AT&T UNIX version and are usually officially licensed.

The boundary between the two development branches of Unix systems is blurred and frequently overlaps. Lately, the two main branches have been converging more and more, and technical innovations are often adopted from the other competing branch. On occasion, operating systems with BSD components will also officially be certified as UNIX by the Open Group (macOS uses BSD code, but as of version Leopard 10.5 is also officially certified as UNIX 03).

History and development of Linux

Linux is clearly the junior in our Linux vs. Unix comparison. This Unix-like operating system was released in 1991 by its developer Linus Torvalds. Technically, at the time the Finnish developer only provided a modular operating system kernel (the Linux kernel). It functions as a central standard interface for a wide variety of hardware and is responsible for memory and process management as well as for multitasking and security features.

The Linux kernel was then made available to the open-source community in 1992 by licensing it under the free GPL license. This licensing sparked further general development that gave rise to a variety of Linux distributions and derivatives. A distribution expands the Linux kernel into a full-fledged operating system with compilers, libraries and interfaces for user interaction. However, stripped-down versions of Linux operating close to the hardware on small devices only require a relatively small amount of additional software.

The GNU Project is a highly influential developer community that works with Linux. GNU/Linux distributions are widely used for desktops and servers. The fact that in the Linux world there is no need to consider restrictive licenses, licensing fees and lengthy licensing procedures is crucial when it comes to the development dynamics of distributions and derivatives. Linux was initially developed for Intel’s x86 hardware processors. However, it is now available for over 20 different CPU types. Linux is also compatible with ARM processors for small and mobile devices (e.g., smartphones, tablets, media players, minicomputers like the Raspberry Pi and various wearable devices).

Unix: adoption, cost, and target audience

Initially, Unix was mainly used in universities and on specific workstations. Later, the operating system became increasingly used on servers and in data centres. Nowadays, Unix service providers mostly focus on paying customers from the private and industrial sector (e.g., financial service providers, large industrial companies, and customers from the health sector). Anyone looking to use Unix in a professional capacity on servers or workstations today will usually buy a proprietary, licensed, certified UNIX version from a manufacturer such as IBM (AIX), Oracle (Oracle Solaris) or Hewlett Packard (HP-UX). These manufacturers offer a perfectly customised complete package of hardware and software. This is how Unix is often run on PA-RISC and Itanium machines. The licensing cost varies depending on the scope of the complete package required, including server hardware and the number of software licenses.

Industry and business customers value stability and security above all else and prefer to use AT&T-style proprietary UNIX systems for business operations. Unix systems will certainly continue to play a role in this market since major companies often have long-term licensing, support, and maintenance contracts with Unix service providers. Not to mention, switching from an individually customised complete Unix system to a different system architecture can be quite costly and comes with some technical risks.

Overall, however, Unix’s popularity and adoption rate has been in a steady decline for some time now. One reason for this has to do with technical development. Modern Windows and Linux systems typically work with the low-cost and currently leading x86 processor architectures which are rapidly evolving and dominating the standard server market today. Meanwhile, traditional server systems (e.g., Itanium machines with System V UNIX systems) have not been making as much technical progress lately and are not exactly known to be cost-effective solutions.

Since Unix systems have always been tailored to specific areas of application and experienced users (e.g., IT professionals, programmers, and system administrators), they have typically played less of a role in the mass market for laptops and desktop computers. That said, despite the decline in its use and its focus on business operations, Unix’s current influence should not be understated. In our Unix vs. Linux comparison, BSD systems have been particularly successful in terms of their adoption. Apple’s macOS uses Unix code, and free Unix derivatives such as FreeBSD are among the most widely used operating systems in the world outside of the laptop and desktop computer market. FreeBSD is increasingly being used for applications such as mail servers, web servers, firewalls, FTP servers and DNS servers. It is installed on routers and NAS hardware.

Linux: adoption, cost, and target audience

Due to its obvious advantages, Linux is becoming increasingly prevalent. Linux is known for its broad hardware support, being open source, its public availability (e.g., CDs, DVDs, internet downloads), being free of charge even for multiple installations, the speed at which it is being further developed, its excellent extensibility and lastly how perfectly it can be adapted to hardware, specific application environments and requirement profiles. In addition, POSIX compatibility makes it easier to migrate from old Unix systems, thus also contributing to the adoption of Linux.

Linux is highly popular for servers. It is estimated that at least half of all servers run on Linux operating systems. There are also paid versions (Red Hat Enterprise Linux) specifically designed for the server market with better, yet sometimes quite expensive, customer support. Linux is also widely used in the mobile sector. The popular Google operating system Android is a distribution with a modified Linux kernel. Small devices (e.g., cell phones, minicomputers, routers) often use trimmed-down Linux versions (embedded Linux systems).

Linux plays a smaller role in the desktop computer sector. It has ranked third among the world’s most popular computer operating systems since 2009. However, this ranking can be deceiving. In July 2020, its market share of worldwide page views was only 1.9% (the data collected was based on internet use via desktop and laptop computers; smartphones and tablets were not included).

While it is true that low-cost Linux desktop computers have been established in some niche markets (e.g., government institutions and organisations), Linux is still generally seen as the preferred solution for hobbyists, serious computer users and IT professionals who want to remain independent of US companies and can handle using the command line. Many users also seem to shy away from the idea of not using Windows or macOS. They do not want to take the time to learn how to use a new operating system or have to switch to other application programs.

Comparing the characteristics and functions of Linux and Unix

When comparing Unix vs. Linux, the first thing that becomes apparent is how similar they are. Both are multi-user systems, allow multitasking and guarantee increased system stability through memory protection. They both provide IT professionals and system administrators with access to sophisticated scripting and a command-line tool for management and programming. Both systems offer mutual compatibilitythrough the POSIX specification. This means, for example, that utility software can be interchanged without a problem, and cross-system migration and porting are significantly easier.

Work in client-server architectures can typically be done quickly and efficiently with Unix. The number of utility software programs available also covers most needs of experienced IT professionals and system administrators. If you cannot find an application that fits your needs, you can program it yourself. Linux users today can benefit from similarly sophisticated systems that are constantly being optimised and equipped with modern features thanks to the open-source community’s development dynamics.

In terms of the software selection, both systems offer a comprehensive core set of utility software and basic software. Linux distributions also offer an integrated, user-friendly package manager. It accesses a software repository with current tested application programs via the internet. A package maintainer handles the maintenance of program packages in an update repository, which contains both free and paid programs. In addition, Linux offers a greater variety of operating systems and user interfaces than Unix, especially for normal desktop users (e.g., the desktop environments KDE and GNOME).

Security in Unix and Linux

When comparing Unix vs. Linux, it is important to mention security. Both are particularly secure operating systems. Their specific system architectures make it much more difficult to cause any serious damage. Permissions and access rights can be managed in a highly differentiated and detailed manner, in addition to user management clearly differentiating users. In the multi-user system, each user has their own data storage which cannot be accessed by any other user. This prevents data from being lost by someone unintentionally deleting it. Users also do not have access to important system files. Both Unix and Linux offer secure remote access via Secure Shell (SSH). Nearly all Unix- and Linux-based operating systems come with a pre-configured SSH program.

Another advantage of both systems is that the number of viruses and malware targeting them is low. The low rate of adoption among desktop users has had a positive effect in this respect since hackers usually specialise in security vulnerabilities found in the most used software and hardware (e.g., Windows programs). However, it appears that Linux systems are now being more frequently targeted by hackers due to their increased use in servers, routers and IoT devices. As such, it is important to regularly fix security vulnerabilities found in the Linux kernel. Unix and Linux servers can also spread malware to Windows PCs in the network.

Comparing the use of Linux and Unix

For many years, there was no standard user interface available for classic Unix versions. However, since the mid-1980s, the X Window System has made it possible to equip individual utility software programs with a GUI (graphical user interface) and for them to be used with a mouse and keyboard. That said, it was not possible to refer to a standard cross-application graphical user interface due to all the different versions out there and the use of different GUIs for individual applications. Today’s Unix systems have access to easy-to-understand desktop environments such as KDE and GNOME.

These are also available for Linux, along with other GUIs. The developer community would like to establish Linux as a universal solution for practically all available platforms if possible and is also working to address a wider target audience with a greater variety of accessible user interfaces. For example, there is a user interface for the desktop environment GNOME that allows you to use Linux in almost the same way as you would useWindows 10.

In both operating systems, it is common for users to use the terminal or command line, especially in Unix. One reason for this is that many administrative tasks can be performed and automated more efficiently with a shell, especially when it comes to servers (even between computers in a network). The standard shell for using the command line in most Linux systems is called Bash, while many Unix systems use the Bourne shell.

Unix vs. Linux: advantages and disadvantages

Advantages of Unix

Advantages of Linux

Stable sophisticated environment, particularly for servers and workstations

Versatile OS, particularly well suited to the server market (dedicated Linux server distributions are available); many clouds use Linux

Runs on many hardware platforms (portability); customised solutions perfectly suited to the hardware

Broad hardware support, regardless of the manufacturer (applies to CPUs, servers, workstations, computers, minicomputers)

Paid UNIX systems are constantly in active development; customer needs are considered

Most distributions are free (CD/DVD, internet download)

Secure (e.g., restricted user rights, encryption)

Secure (e.g., restricted user rights, encryption)

Sophisticated scripting (shell)

Sophisticated scripting (shell)

Great for programmers and system administrators

Great for programmers and system administrators; multiple easy-to-use GUIs for desktop users

Large selection of programs and tools (often already included in the OS)

Large selection of programs and tools (often already included in the OS)

Great for business applications

Frequent updates; security vulnerabilities are quickly addressed

The POSIX standard enables Unix applications to also run on Linux (possible to migrate)

The POSIX standard enables Linux applications to also run on Unix (possible to migrate)

 

Minimal hardware requirements; good system performance

 

Portable versions available with no installation (e.g., on DVDs, USB sticks)

Disadvantages of Unix

Disadvantages of Linux

Limited target audience since it is designed for experienced users and IT professionals

A familiarisation period is necessary for those new to Linux; users switching to Linux sometimes have to manage without the software they are used to

Many (specialised) solutions on the server market are subject to a fee and are tied to a specific manufacturer’s hardware

In the server market, there may be higher support fees for commercial Linux distributions

Generally, there are more hardware requirements (especially for commercial and license-based systems)

Linux has security vulnerabilities and is at risk for malware (servers are particularly at risk)

Rather infrequent updates and slow development

Drivers for new hardware (computers, graphics cards) are sometimes released slowly

Declining user numbers, partly being replaced by Linux (especially in the server market)

Tendency towards fragmentation in Linux development (large number of Linux distributions)

Virtually irrelevant in the desktop computer market

Low market share of desktop computers and laptops


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