Unix vs. Linux

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.

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).

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)

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).

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).

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.

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.

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 com­pat­ib­il­ity through 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).

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.

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 use Windows 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.