Unix Vs Linux Difference and comparison

UNIX is copyrighted name only big companies are allowed to use the UNIX copyright and name, so IBM AIX and Sun 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.

Most UNIX systems are commercial in nature.

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" do not approve of the construction "Unix-like", and consider it 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 etc) + installation & management tools + GNU c/c++ Compilers + Editors (vi) + 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 comes with A-Z programs such as editor, compilers etc. For example HP-UX or Solaris comes with A-Z programs.

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 UNIX like operating systems are not free (but this is changing fast, for example OpenSolaris UNIX). However, some Linux distributions such as Redhat / Novell 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, Apple OS X is most popular UNIX operating system for desktop usage.

Security Firewall Software

Linux comes with open source netfilter/iptables 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, and cpio etc.

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).

System Administration Tools

1. UNIX comes with its own tools such as SAM on HP-UX.
2. Suse Linux comes with Yast
3. Redhat Linux comes with its own gui tools called redhat-config-*.

However, editing text config file and typing commands are most popular options for sys admin work under UNIX and Linux.

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

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) and other development tools such as Perl 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 Solairs
4. Mac OS X
5. IRIX

Linux Distribution (Operating System) Names

A few popular names:

1. Redhat Enterprise Linux
2. Fedora Linux
3. Debian Linux
4. Suse Enterprise Linux
5. Ubuntu Linux

Common Things Between Linux & UNIX

Both share many common applications such as:

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

A Sample UNIX Desktop Screenshot

Fig.01: UNIX Desktop - IRIX 6.5 Desktop

A Sample Linux Desktop Screenshot

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 etc

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.

Linux	Unix 5
What is it?	Linux is an example of Open Source software development and Free Operating System (OS).	Unix is an operating system that is very popular in universities, companies, big enterprises etc.
Cost	Linux can be freely distributed, downloaded freely, distributed through magazines, Books etc. There are priced versions for Linux also, but they are normally cheaper than Windows.	Different flavors of Unix have different cost structures according to vendors
User	Everyone. From home users to developers and computer enthusiasts alike.	Unix operating systems were developed mainly for mainframes, servers and workstations except OSX, Which is designed for everyone. The Unix environment and the client-server program model were essential elements in the development of the Internet
Manufacturer	Linux kernel is developed by the community. Linus Torvalds oversees things.	Three bigest distributions are Solaris (Oracle), AIX (IBM) & HP-UX Hewlett Packard. And Apple Makes OSX, an unix based os..
Usage	Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers.	The UNIX operating system is used in internet servers, workstations & PCs. Backbone of the majority of finance infastructure and many 24x365 high availability solutions.
Development and Distribution	Linux is developed by Open Source development i.e. through sharing and collaboration of code and features through forums etc and it is distributed by various vendors.	Unix systems are divided into various other flavors, mostly developed by AT&T as well as various commercial vendors and non-profit organizations.
GUI	Linux typically provides two GUIs, KDE and Gnome. But there are millions of alternatives such as LXDE, Xfce, Unity, Mate, twm, ect.	Initially Unix was a command based OS, but later a GUI was created called Common Desktop Environment. Most distributions now ship with Gnome.
File system support	Ext2, Ext3, Ext4, Jfs, ReiserFS, Xfs, Btrfs, FAT, FAT32, NTFS	jfs, gpfs, hfs, hfs+, ufs, xfs, zfs format
Text mode interface	BASH (Bourne Again SHell) is the Linux default shell. It can support multiple command interpreters.	Originally the Bourne Shell. Now it's compatible with many others including BASH, Korn & C.
Price	Free but support is available for a price.	Some free for development use (Solaris) but support is available for a price.
Security	Linux has had about 60-100 viruses listed till date. None of them actively spreading nowadays.	A rough estimate of UNIX viruses is between 85 -120 viruses reported till date.
Threat detection and solution	In case of Linux, threat detection and solution is very fast, as Linux is mainly community driven and whenever any Linux user posts any kind of threat, several developers start working on it from different parts of the world	Because of the proprietary nature of the original Unix, users have to wait for a while, to get the proper bug fixing patch. But these are not as common.
Processors	Dozens of different kinds.	x86/x64, Sparc, Power, Itanium, PA-RISC, PowerPC and many others.
Examples	Ubuntu, Fedora, Red Hat, Debian, Archlinux, Android etc.	OS X, Solaris, All Linux
Architectures	Originally developed for Intel's x86 hardware, ports available for over two dozen CPU types including ARM	is available on PA-RISC and Itanium machines. Solaris also available for x86/x64 based systems.OSX is PowerPC(10.0-10.5)/x86(10.4)/x64(10.5-10.8)
Inception	Inspired by MINIX (a Unix-like system) and eventually after adding many features of GUI, Drivers etc, Linus Torvalds developed the framework of the OS that became LINUX in 1992. The LINUX kernel was released on 17th September, 1991	In 1969, it was developed by a group of AT&T employees at Bell Labs and Dennis Ritchie. It was written in “C” language and was designed to be a portable, multi-tasking and multi-user system in a time-sharing configuration.

Contents: Linux vs Unix

1 History of Unix vs. Linux 2 Usage of Linux and Unix 3 Linux - Unix Differences in Cost & Distribution 4 Threats and Security: Unix vs. Linux

5 Market and future of Linux and Unix 6 Related Video 7 Shop For 8 References

History of Unix vs. Linux

Evolution of Unix (click to enlarge)

In 1960, the Massachusetts Institute of Technology, AT&T Bell Labs, and General Electric were working on an experimental operating system called Multiplexed Information and Computing Service or MULTICS. This was designed to run on the GE-645 mainframe computer. But it performed poorly. AT&T Bell Labs called off this project and deployed its resources elsewhere. But Ken Thompson, one of the developers from Bell Labs continued to develop for the GE-645 mainframe, and wrote a game for that computer called Space Travel. But the game was too slow on the GE machine and expensive also, costing $75 per execution. So he re-wrote the game in assembly language for Digital Equipment Corporation'sPDP-7 with help from Dennis Ritchie.

This experience, combined with his work on the Multics project, led Thompson to start a new operating system for the PDP-7 and they developed a file system as well as the new multi-tasking operating system itself with the help of a small team of developers. They included a command line interpreter and some small utility programs. This was named as UNICS in 1970, and later change into UNIX.

In 1985, Richard Stallman created the Free Software Foundation and developed theGNU General Public License (GNU GPL), in order to spread software freely. Many of the programs required in an OS (such as libraries, compilers, text editors, a UNIX shell, and a windowing system) were completed by the early 1990s, but few elements such as device drivers, daemons, and the kernel were incomplete. In 1991, Linus Torvalds began to work on MINIX, a Unix-like OS, whose code was freely available under GNU GPL project. Then he developed the first LINUX kernel and released it on 17 September 1991, for the Intel x86 PC systems. This kernel included various system utilities and libraries from the GNU project to create a usable operating system. All underlying source code can be freely modified and used.

Usage of Linux and Unix

Linux OS is great for small- to medium-sized operations, and today it is also used in large enterprises where UNIX was considered previously as the only option. A few years back, Linux was considered as an interesting academic project, but most big enterprises, where networking, multiple user computing is the main concern;people didn't consider Linux as an option. But today, with major software vendors porting their applications to Linux, and as it can be freely distributed, the OS has entered the mainstream as a viable option for Web serving and office applications.

But there are some circumstances where UNIX is the obvious choice, or used to be. If an enterprise used massive symmetric multiprocessing systems, or systems with more than eight CPUs, they needed to run UNIX in the past. UNIX was far more capable in handling all the processes more effectively than Linux. However since 2004 more of the world's biggest supercomputers now run Linux than unix. Since 2011 Linux powers over 90% of the top 500 servers. It runs also on the biggest (as of 2011): RIKEN Advanced Institute for Computational Science Cores: 705024 Power: 12659.89 kW Memory: 1410048 GB

Linux - Unix Differences in Cost & Distribution

Linux can be freely distributed, as it is an open Source OS. So anyone can get a copy of Linux from books, magazines, or from the internet also. For server versions,organizations typically pay distributors for a support contract, not the software. The major distributors are RED HAT, Mandrake, and SUSE. For server hardware, IBM,HP, Dell are the major ones.

UNIX is costly as compared to Linux; the midrange UNIX servers are priced in between $25,000 and $249,999 (including hardware). The major distributors are HP, IBM and SUN. A high end UNIX server can cost up to $500,000. According to IDC, Gartner, IBM is the market leader in UNIX servers, HP is in 2nd position and SUN is in the third position.

Commercial UNIX is usually custom written for each system, making the original cost quite high, whereas Linux has base packages also. In this respect, Linux is closer in its model to Windows than a commercial UNIX OS is. At the time of purchasing a UNIX server, users get a Vendor assistance plan on setting up and configuring the system. But with Linux, Vendor support must be purchased separately.

Threats and Security: Unix vs. Linux

Both of the operating systems are vulnerable to bugs but Linux is far more responsive in dealing with the threats. Linux incorporated many of the same characteristics and functions found in UNIX, including the segmentation of the user domain in a multi-user environment, the isolation of tasks in a multi-tasking environment, a password system that can be encrypted and/or located remotely and much more. As Linux is an open system OS, the bugs can be reported by anyone in the user/developers forum, and within days it can be fixed. But for UNIX, this is not the case, and user has to wait for a while, to get the proper bug fixing patch. The open source community delivers faster because it does not have to go through the endless development cycles of commercial-based operating systems.

At the same time, as an open source operating system, it is supported by tens of thousands of developers worldwide. To reiterate, this allows for better innovation and quicker-to-market features than anything UNIX can provide.

Market and future of Linux and Unix

According to International Data Corp. (IDC).Linux has grown faster than any other server OS over the past few years. Linux user base is estimated to be about more than 25 million machines, compared to 5.5 million for combined UNIX installations.
Linux is gaining popularity because of its application in embedded technologies, free and easily availability. To compete with Linux, vendors such as HP, IBM, Sun are making customized UNIX with graphical user interface and user friendly interface which is also compatible with Linux. The main UNIX vendors--IBM, Sun, and Hewlett-Packard are already putting Linux interoperability features into future releases of AIX, Solaris, and HP-UX.

Also :-

Well to be specific Linux is considered as Unix-Like Operating system coming under the category of UNIX clones. A clone is a program (i.e., an operating system or an application program) that has functions and behavior similar to another program but which does not contain source code from that program.

License

(History)

UNIX was developed and evolved more as a licensed version or proprietary software.It was used more for commercial purpose. This was one of the reason for Linux to be developed as a free operating system by Linus Torvalds. Once the Linux kernel was developed later it was released under GPL (GNU General Public License) integrated with libraries, compilers, text editors transforming it into an operating system and releasing worldwide as opensource.

(Present)

Even now most UNIX operating system are proprietary as they are mostly commercially used like Oracle's Solaris, Hewlett-Packard's HP-UX, and IBM's AIX. Well there are also some open source OS for UNIX like Open Solaris, OpenBSD.

Coming to Linux kernel you can find a long list of free and opensource operating system like CentOS, Scientific Linux, Fedora, OpenSUSE, Ubuntu etc. For commercial version there is Red hat Linux, SUSE etc.

Hardware Architectures

Linux can be much more flexible as compared to Unix as they can be installed on almost any hardware(NOT ALL). But Unix OS are very restricted when it comes for the supported hardware for example HP-UX is available on PA-RISC and Itanium machines. Solaris is available on SPARC and x86. AIX is only for power processors etc.

Kernel

Kernel can be considered the HEART of any operating system. Now as explained in the history part Linux is just an kernel and integrating it with other features like libraries, editors, compilers makes it an Operating System. 

The source code for most UNIX kernel specially commercial versions are not available freely. On the other hand most Linux OS source code are free available under the GPL and can be read, modified and used by any and everyone.

Patches and updates

Linux being open source their patches are released in the form of source code which can be manually and updated. Now one negative point on this one can be that these patches are not much tested for bug as compared to commercial version of UNIX. In case of Linux based on the feedback of users and developers the bugs are fixed and patches are released. But in case of UNIX developers test the patch multiple times before releasing it to the update server of their OS.

NOTE: In case of commercial version of Linux the patches are checked and verifed prior releasing it to their relative OS. Re-revised version of OS are released at regular intervals with all the bug fixes as developed.

UNIX OS seems to be more stable in terms of releasing patches or upgrades and the code works for longer time for the same driver as compared to Linux.

Filesystem support

Linux has very high scalibility be it in terms of hardware architectures or filesystem as it suports many of them unlike UNIX OS which supports very few type of filesystem.

Filesystem supported under Linux

adfs, affs, autofs,  cifs,  coda, coherent,  cramfs,  debugfs,  devpts,  efs, ext, ext2, ext3, hfs, hpfs, iso9660, jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc,  qnx4,  ramfs,  reiserfs,  romfs,  smbfs, sysv,  tmpfs,  udf, ufs, umsdos, usbfs, vfat, xenix, xfs, xiafs

Filesystem supported under UNIX

OS	File system
AIX	jfs, gpfs
HP-UX	hfs, vxfs
Solaris	ufs, zfs
Irix	xfs

System Administration Tools

Well mostly Linux/Unix are preferred to be used on CLI rather than GUI in corporate world. But still to make things easier both the OS offer different type of GUI tools for administrators.

In Red Hat - system-config-*

In HP-UX - SAM (System Administration Manager)

In SUSE - YaST

As per the command perspective, there can be seen many differences 

For example to install a package

In Red Hat - rpm -i file

In Solaris - pkgadd -d pkgfile

IN HP-UX - swinstall -s depot software

IN AIX- installp - [-c] FileSet

System Initialization scripts

Location of the system init scripts is different on both the types of OS

System	Location
HP-UX	/sbin/init.d
AIX	/etc/rc.d/init.d
Irix	/etc/init.d
Solaris	/etc/init.d
Red Hat	/etc/rc.d/init.d
SUSE	/etc/rc.d/init.d
Debian	/etc/init.d
Slackware	/etc/rc.d

Cost

As discussed in earlier part of this article most UNIX use their own hardware for their OS their cost price rises accordingly where on the opposite side getting a commercial version of Linux OS is very much cheaper.

Examples for Linux and UNIX

UNIX	Linux
HP-UX	Red Hat
AIX	Debian
Irix	Ubuntu
Solaris	SUSE
BSD	CentOS
	Fedora
	Scientific Linux
	Slackware