Linux - An Anternative Operating System?

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. Linux was originally developed as a free operating system for Intel x86-based personal computers. It has since been ported to more computer hardware platforms than any other operating system. Linux is the kernel of an operating system. Linux was built on the Unix tradition. Linux was originally developed by Linus Torwalds of Finland, who currenctly owns the Linux trademark. Linux stands for Linus' Unix. Using the open source code of the Linux kernel, people have been developing operating systems based on the Linux kernel. These are called the "Linux distributions".

In 1991, in Helsinki, Linus Torvalds began a project that later became the Linux kernel. It was initially a terminal emulator, which Torvalds used to access the large UNIX servers of the university.
Linux and most GNU software are licensed under the GNU General Public License (GPL). The GPL requires that anyone who distributes Linux must make the source code (and any modifications) available to the recipient under the same terms. Typically Linux is packaged in a format known as a Linux distribution for desktop and server use. Some popular mainstream Linux distributions include Debian (and its derivatives such as Ubuntu), Fedora and openSUSE.

Linux Advantages
  •  Low cost: You don’t need to spend time and money to obtain licenses since Linux and much of its software come with the GNU General Public License. You can start to work immediately without worrying that your software may stop working anytime because the free trial version expires. Additionally, there are large repositories from which you can freely download high quality software for almost any task you can think of.
  • Stability: Linux doesn’t need to be rebooted periodically to maintain performance levels. It doesn’t freeze up or slow down over time due to memory leaks and such. Continuous up-times of hundreds of days (up to a year or more) are not uncommon.
  • Performance: Linux provides persistent high performance on workstations and on networks. It can handle unusually large numbers of users simultaneously, and can make old computers sufficiently responsive to be useful again.
  • Network friendliness: Linux was developed by a group of programmers over the Internet and has therefore strong support for network functionality; client and server systems can be easily set up on any computer running Linux. It can perform tasks such as network backups faster and more reliably than alternative systems.
  • Flexibility: Linux can be used for high performance server applications, desktop applications, and embedded systems. You can save disk space by only installing the components needed for a particular use. You can restrict the use of specific computers by installing for example only selected office applications instead of the whole suite.
  • Compatibility: It runs all common Unix software packages and can process all common file formats.
  • Choice: The large number of Linux distributions gives you a choice. Each distribution is developed and supported by a different organization. You can pick the one you like best; the core functionalities are the same; most software runs on most distributions.
  • Fast and easy installation: Most Linux distributions come with user-friendly installation and setup programs. Popular Linux distributions come with tools that make installation of additional software very user friendly as well.
  • Full use of hard disk: Linux continues work well even when the hard disk is almost full.
  • Multitasking: Linux is designed to do many things at the same time; e.g., a large printing job in the background won’t slow down your other work.
  • Security: Linux is one of the most secure operating systems. “Walls” and flexible file access permission systems prevent access by unwanted visitors or viruses. Linux users have to option to select and safely download software, free of charge, from online repositories containing thousands of high quality packages. No purchase transactions requiring credit card numbers or other sensitive personal information are necessary.
  • Open Source: If you develop software that requires knowledge or modification of the operating system code, Linux’s source code is at your fingertips. Most Linux applications are Open Source as well.
User interface

Users operate a Linux-based system through a command line interface (CLI), a graphical user interface (GUI), or through controls attached to the associated hardware, which is common for embedded systems. For desktop systems, the default mode is usually a graphical user interface, by which the CLI is available through terminal emulator windows or on a separate virtual console.
On desktop systems, the most popular user interfaces are the extensive desktop environments KDE Plasma Desktop, GNOME, and Xfce, though a variety of additional user interfaces exist. Most popular user interfaces are based on the X Window System, often simply called "X". It provides network transparency and permits a graphical application running on one system to be displayed on another where a user may interact with the application.
A Linux distribution, commonly called a "distro", is a project that manages a remote collection of system software and application software packages available for download and installation through a network connection. This allows users to adapt the operating system to their specific needs. Distributions are maintained by individuals, loose-knit teams, volunteer organizations, and commercial entities. A distribution is responsible for the default configuration of the installed Linux kernel, general system security, and more generally integration of the different software packages into a coherent whole. Distributions typically use a package manager such as dpkg, Synaptic, YAST, or Portage to install, remove and update all of a system's software from one central location.
Programming on Linux
Most Linux distributions support dozens of programming languages. The original development tools used for building both Linux applications and operating system programs are found within the GNU toolchain, which includes the GNU Compiler Collection (GCC) and the GNU build system.  Most distributions also include support for PHP, Perl, Ruby, Python and other dynamic languages. While not as common, Linux also supports C# (via Mono), Vala, and Scheme.
Linux distributions have long been used as server operating systems, and have risen to prominence in that area. Linux distributions are the cornerstone of the LAMP server-software combination (Linux, Apache, MySQL, Perl/PHP/Python) which has achieved popularity among developers, and which is one of the more common platforms for website hosting.
Cost

The following distributions are available for free (without cost): aLinux, Alpine Linux, ALT Linux, Annvix, Arch Linux, Ark Linux, Asianux, BLAG Linux and GNU, Bodhi Linux, Caixa Mágica, CentOS, CRUX, Damn Small Linux, Debian, DeLi Linux, Devil-Linux, dyne:bolic, EasyPeasy, Edubuntu, Elive, EnGarde Secure Linux, Fedora, Finnix, Foresight Linux, Freespire, Frugalware, Gentoo, gNewSense, gnuLinEx, GoboLinux, Gobuntu, Impi Linux, Kanotix, Knoppix, KnoppMyth, Kubuntu, Kurumin, Linux Mint, Lunar Linux, Micro Core Linux, Mageia. MintPPC, Musix GNU/Linux, Network Security Toolkit, NimbleX, NUbuntu, openSUSE, Pardus, Parsix, PCLinuxOS, Puppy Linux, Sabayon Linux, Scientific Linux, sidux, Slackware, Slax, SliTaz GNU/Linux, Source Mage GNU/Linux, Symphony OS, SYS, Tiny Core Linux, Tor-ramdisk, Trustix, Ubuntu, Ututo, Super OS, Xubuntu, XBMC Live, Yoper, Zenwalk and OpenWrt.
The following distributions have several editions, some of which are without cost and some of which do cost money: ClearOS, Mandriva Linux, MEPIS and Red Flag Linux.
The following distributions cost money: Novell Open Enterprise Server, Red Hat Enterprise Linux, Rxart,SUSE Linux Enterprise,
The following distribution had at least one version that used to cost money: Caixa Mágica (now freely-available), Elive (now freely-available), Xandros (discontinued), Linspire (discontinued).

Commands

For POSIX compliant (or partly compliant) systems like FreeBSD, Linux, Mac OS X or Solaris, the basic commands are the same because they are standardized.
descriptionFreeBSDLinuxMac OS XSolarisWindows (cmd)Windows (powershell)Windows (cygwin, SFU or MKS)
list directorylslslslsdirdir & ls & Get-ChildItemls
clear consoleclearclearclearclearclsclearclear
copy file(s)cpcpcpcpcopycp & Copy-Itemcp
move file(s)mvmvmvmvmovemv & Move-Itemmv
rename file(s)mvmv, renamemvmvren, renameren, mvmv
delete file(s)rmrmrmrmdel (erase)rm & Remove-Itemrm
delete directoryrmdirrmdirrmdirrmdirrd (rmdir)rmdirrmdir
create directorymkdirmkdirmkdirmkdirmd (mkdir)mkdirmkdir
change current directorycdcdcdcdcd (chdir)cd & Set-Locationcd
run shell script with new shellsh file.shsh file.shsh file.shsh file.shcmd /c file.cmd?sh file.sh
kill processeskill, killallkillall, pkill, kill, skillkill, killallkill, pkilltaskkilltaskkillkill
change process prioritynicenice, chrtnicenicestart /low, start /normal, start /high, start /realtime?nice
change io priority[c 1]ionicenice[c 2]????
create file systemnewfsmkfsmkfsnewfsformat??
file system check and recoveryfsckfsckfsckfsckchkdsk??
create software raidatacontrol, gmirror, zfs create(mdadm—create)diskutil appleRAIDmetainit, zfs creatediskpart (mirror only)diskpart (mirror only)?
mount devicemountmountmount, diskutil mountmountmountvolmount & New-PSDrive?
unmount deviceumountumountumount, diskutil unmount(disk)umountmountvol /dRemove-PSDrive?
mount file as block devicemdconfig + mountmount -o loophdidlofiadm + mount???
show network configurationifconfigip addr, ifconfigifconfigifconfigipconfigipconfig?
show network routerouteip routerouterouteroute??
trace network routetraceroutetraceroutetraceroutetraceroutetracerttracert?
trace network route with pingstraceroute -Itraceroute -I & mtrtraceroute -Itraceroute -Ipathpingpathping?
descriptionFreeBSDLinuxMac OS XSolarisWindows (cmd)Windows (powershell)Windows (cygwin, SFU or MKS)

Popular distributions

Well-known Linux distributions include:
  • Arch Linux, a minimalist rolling release distribution targetted at experienced Linux users, maintained by a volunteer community and primarily based on binary packages in the tar.gz and tar.xz format.
  • Debian, a non-commercial distribution maintained by a volunteer developer community with a strong commitment to free software principles
  • Fedora, a community distribution sponsored by Red Hat
    • Red Hat Enterprise Linux, which is a derivative of Fedora, maintained and commercially supported by Red Hat.
      • CentOS, a distribution derived from the same sources used by Red Hat, maintained by a dedicated volunteer community of developers with both 100% Red Hat-compatible versions and an upgraded version that is not always 100% upstream compatible
      • Oracle Enterprise Linux, which is a derivative of Red Hat Enterprise Linux, maintained and commercially supported by Oracle.
    • Mandriva, a Red Hat derivative popular in France and Brazil, today maintained by the French company of the same name.
      • PCLinuxOS, a derivative of Mandriva, grew from a group of packages into a community-spawned desktop distribution.
  • Gentoo, a distribution targeted at power users, known for its FreeBSD Ports-like automated system for compiling applications from source code
  • openSUSE a community distribution mainly sponsored by Novell.
  • Slackware, one of the first Linux distributions, founded in 1993, and since then actively maintained by Patrick J. Volkerding.
  • Damn Small Linux, "DSL" is a Biz-card Desktop OS
DistroWatch attempts to include every known distribution of Linux, whether currently active or not; it also maintains a ranking of distributions based on page views, as a measure of relative popularity.
A Live Distro or Live CD is a Linux distribution that can be booted from a compact disc or other removable medium (such as a DVD or USB flash drive) instead of the conventional hard drive. Some minimal distributions such as tomsrtbt can be run directly from as little as one floppy disk without needing to change the system's hard drive contents.Many popular distributions come in both "Live" and conventional forms (the conventional form being a network or removable media image which is intended to be used for installation only). This includes SUSE, Ubuntu, Linux Mint, MEPIS, Sidux, and Fedora. Some distributions, such as Knoppix, Devil-Linux, SuperGamer, and dyne:bolic are designed primarily for Live CD, Live DVD, or USB flash drive use.
Difference Between Linux and UNIX
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. 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.
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.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.
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.
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.
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.
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
  •     UNIX comes with its own tools such as SAM on HP-UX.
  •     Suse Linux comes with Yast
  •     Redhat Linux comes with its own gui tools called redhat-config-*.
System Startup Scripts
Almost every version of UNIX and Linux comes with system initialization script but they are located in different directories:
  •     HP-UX - /sbin/init.d
  •     AIX - /etc/rc.d/init.d
  •     Linux - /etc/init.d
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:
  •     GUI, file, and windows managers (KDE, Gnome)
  •     Shells (ksh, csh, bash)
  •     Various office applications such as OpenOffice.org
  •     Development tools (perl, php, python, GNU c/c++ compilers)
  •     Posix interface
A Sample UNIX Desktop Screenshot
A Sample Linux Desktop Screenshot
References:
en(dot) wikipedia(dot) org/wiki/List_of_Linux_distributions
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