Difference Between Linux and UNIX

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What is the difference between Linux and UNIX operating systems?

UNIX is a copyrighted name, and only big companies are allowed to use the UNIX copyright and name. For example, Apple macOS, IBM AIX, and Sun/Oracle Solaris and HP-UX all are UNIX operating systems. The Open Group holds the UNIX trademark in trust for the industry and manages the UNIX trademark licensing program. Let us see difference between Linux and UNIX OS in this quick tutorial.
Tutorial details
Difficulty level Easy
Root privileges No
Requirements None
OS compatibility AIX AlmaLinux Alpine Amazon Linux Arch CentOS Debian Fedora FreeBSD HP-UX Linux macOS Mint Mint NetBSD OpenBSD openSUSE Pop!_OS RHEL Rocky Slackware Stream SUSE Ubuntu Unix WSL
Est. reading time 6 minutes
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Difference Between Linux and UNIX

Most UNIX systems are commercial in nature. You need to pay for support, software, training, and more. On the other hand, the Linux kernel is free to download and install on your systems free of cost.

Linux is a UNIX Clone

But if you consider Portable Operating System Interface (POSIX) standards, then Linux can be considered as UNIX. To quote from Official Linux kernel README file:

Linux is a Unix clone written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX compliance.

However, “Open Group” does not approve of the construction “Unix-like” and considers it a misuse of their UNIX trademark.

Linux is just a kernel

Linux is just a kernel. All Linux distributions includes GUI system + GNU utilities (such as cp, mv, ls,date, bash and more) + installation management tools + GNU c/c++ compilers + Editors (vi/ed/nano) + and various applications (such as OpenOffice, Firefox). However, most UNIX operating systems are considered as a complete operating system as everything come from a single source or vendor.

As I said earlier, Linux is just a kernel, and Linux distribution makes it complete usable operating systems by adding various applications. Most UNIX operating systems come with A-Z programs such as editor, compilers, and more. For example, HP-UX or Solaris comes with A-Z programs.

BSD family of operating systems

No discussion related to Unix is ever completed without discussing a free version of Unix. Typically all *BSD family of operating systems are available free of cost and try to as close as possible to original Unix concepts. BSD family of operating systems based on BSD, the version of UNIX developed at the University of California, Berkeley. We have several operating systems that are based on BSD, including FreeBSD, OpenBSD, NetBSD, MidnightBSD, Darwin, and DragonFly BSD. Like Unix operating systems, the BSD family of an operating system typically comes with all required applications from a single project. An additional app/software can be installed using ports or binary package system.

License and cost

Linux is Free (as in beer [freedom]). You can download it from the Internet or redistribute it under GNU licenses. You will see the best community support for Linux. Most certified UNIX like operating systems are not free (but this is changing fast, for example, OpenSolaris UNIX). However, some Linux distributions such as Redhat (RHEL) / Novell (SUSE) provides additional Linux support, consultancy, bug fixing, and training for additional fees.

User-Friendly

Linux is considered as most user friendly UNIX-like operating systems. It makes it easy to install sound card, flash players, and other desktop goodies. However, macOS (Apple OS X) is most popular UNIX operating system for desktop and laptop users.

Security Firewall Software

Linux comes with open source netfilter/iptables/nftables based firewall tool to protect your server and desktop from the crackers and hackers. UNIX operating systems comes with its own firewall product (for example Solaris UNIX comes with ipfilter based firewall) or you need to purchase a 3rd party software such as Checkpoint UNIX firewall.

Backup and Recovery Software

UNIX and Linux comes with different set of tools for backing up data to tape and other backup media. However, both of them share some common tools such as tar, dump/restore, cpio and more.

File Systems

  • Linux by default supports and use ext3 or ext4 file systems.
  • UNIX comes with various file systems such as jfs, gpfs (AIX), jfs, gpfs (HP-UX), jfs, gpfs (Solaris), zfs and more.

System Administration Tools

  1. UNIX comes with its own tools such as SAM on HP-UX or smitty on IBM AIX.
  2. SUSE Linux comes with Yast/Yast2
  3. Red hat Linux comes with its own gui tools called redhat-config-*.

However, editing text config file and typing commands are most popular options for sysadmin work under Linux and Unix-like systems.

System Startup Scripts

Almost every version of UNIX and Linux comes with system initialization script but they are located in different directories:

  1. HP-UX – /sbin/init.d
  2. AIX – /etc/rc.d/init.d
  3. Linux – /etc/init.d. However, newer system uses systemd instead of /etc/init.d/ based script.

End User Perspective

The differences are not that big for the average end-user. They will use the same shell (e.g., BASH or KSH), text editors such as vim, and other development tools such as Perl, PHP, Python 3.x or Eclipse development tool.

System Administrator Perspective

Again, the differences are not that big for the system administrator. However, you may notice various differences while performing the following operations:

  1. Software installation procedure
  2. Hardware device names
  3. Various admin commands or utilities
  4. Software RAID devices and mirroring
  5. Logical volume management
  6. Package management
  7. Patch management

UNIX Operating System Names

A few popular names:

  1. HP-UX
  2. IBM AIX
  3. Sun Solaris (now Oracle Solaris)
  4. Apple Mac OS X (now macOS)
  5. IRIX

Linux Distribution (Operating System) Names

A few popular names:

  1. Red hat Enterprise Linux
  2. Fedora Linux
  3. Debian Linux
  4. Suse Enterprise Linux
  5. Ubuntu Linux
  6. Arch Linux
  7. Gentoo Linux

Common Things Between Linux and UNIX

Both share many common applications such as:

  1. GUI, file, and windows managers (KDE, Gnome)
  2. Shells (ksh, csh/tcsh, bash)
  3. Various office applications such as OpenOffice.org/libreoffice.org, and more
  4. Development tools (perl, php, python, ruby, GNU c/c++ compilers)
  5. Posix interface

A Sample UNIX Desktop Screenshot

UNIX Desktop - IRIX 6.5 Desktop

Fig.01: UNIX Desktop - IRIX 6.5 Desktop

A Sample Linux Desktop Screenshot

Linux KDE desktop environment

Fig.02: Linux KDE desktop environment

UNIX and Linux Hardware

Commercial UNIX hardware has more advanced initial boot options such as:

  • Decide how to boot
  • Check system health
  • Set hardware parameters
  • Hard disk encrption and security

The BIOS that is standard in PCs which is used by Linux has few, of these features. UNIX hardware or servers are pretty expensive as compare to Linux server systems.

Unix Vs. Linux: What’s the Difference?

Table 1: What are the differences between Linux and Unix?
Factor Linux Unix
Cost Free Different versions of Unix have varying costs/pricing, according to vendors.
Licensing model GPL (open source) Proprietary
Viruses/Malware Limited amount of virus/malware exists Again, a limited amount of virus/malware exists.
Architectures support ARM, x86/x64, Power, Sparc and 100+ architectures ARM, x86/x64, Sparc, Power, and others.
File systems support ext{2,3,4}, zfs, xfs, btrfs, FAT32, NTFS and more UFS, zfs, APFS, JFS and more.
Source code Available to anyone to download, edit
, and redistribute source code under GPL and
other approved open source licenses.
Proprietary and closed source code, and you cannot redistribute it.
Sysadmin tools Yast (SUSE), redhat-config-* and editing config files SAM on HP-UX, smitty on IBM AIX and other GUI based tools
GUI/desktop examples GTK-based (GNOME, Xfce and others),
QT-based (KDE Plasma, Lumina, LXQt and others)
Motif-based (CDE, VUE and others), Aqua (macOS)
Default shell bash ksh, csh or zsh
OS Examples CentOS, RHEL, Fedora, Arch,
OpenSUSE, SUSE, Chrome OS, Android, and 100+ other distros
macOS, Solaris, HP-UX, IBM AIX, SunOS and others

Conclusion

Following documents or URL should help anyone to get more idea:

(Image credit IRIX and KDE wikipedia articles)

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I'm Vivek Gite, and I write about Linux, macOS, Unix, IT, programming, infosec, and open source. Subscribe to my RSS feed or email newsletter for updates.

313 comments… add one
  • Dips Jan 5, 2016 @ 8:57

    This is very niceeeeeeeeeeee…………
    Eaisly understood format……….

  • Tanu Jan 5, 2016 @ 9:00

    Thanks alot for your valuable information..,,………..

  • Amola funmilola I. Jan 12, 2016 @ 17:29

    I’ve got enough point to convince my ICT lecturer. Thanks….

  • curious Jan 24, 2016 @ 18:26

    Whenever i am searching about basics of unix, every other search comes up with basics of linux.
    is it because both of the are similar at base level? or am i missing something? since i have just started learning about unix, i am a bit confused whether leaning about one makes you understand the other then?

  • rusalika silas Jul 11, 2016 @ 16:47

    yes unix is part of lunix

  • manoj Dec 2, 2016 @ 5:43

    its very informative and clear. using this article i have all the answers about my doubt. thanks a lot.

  • Moosecat Jan 21, 2017 @ 14:21

    I like FreeBSD!

  • Ian Jan 26, 2017 @ 17:32

    Article is seriously flawed by omitting discussion of modern Unix-derived open-source systems such as OpenBSD (the guys who gave you OpenSSH, the PF firewall and other innovations), FreeBSD and NetBSD, all derived from Berkeley Unix, a version developed at UC Berkeley in the late 1970’s.

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