Linux+: Operating System Intro 03 – Linux Linux is an Operating System (OS) similar to UNIX. Like UNIX, Linux follows the Portable Operating System Interface (POSIX) standards to create a standard for compatibility between various Operating Systems. At the University of Helsinki in Finland, in 1991, a 21-year-old student wrote his own OS based on Mini-UNIX (Minux or Minix). The student, Linus Torvalds, created the Linux kernel. The Linux kernel is available for all major processor platforms. At this point, since Linux consisted of a kernel only, system components would come from the Free Software Foundation (FSF). These programs were for the “Genuinely Not UNIX” or “GNU’s Not UNIX” (GNU) project. Linux was made as open source software. Open source software is a standard set forth by the Open Source Initiative (OSI) to produce free software. Because the software is free it is believed that the programmers can produce bug free code and does not want financial gain. If bugs do exist it is up to the users to find the bugs and fix them. Because the software is free there is a large base of users that can assure that bugs are found and ultimately fixed. NOTE: Do not confuse the GNU project as promoting software for no fee. The term “free” is meant to allow that the software is open source and usable by all. It is possible to charge a fee for the software as shown on the GNU website at: http://www.gnu.org/philosophy/selling.html. For a program to be OSI certified there are a few items that the programmer and program must conform to: Royalties cannot be gained from the program, as it is free Source code must be available Modifications can be made, but the program name cannot change Access to program and source code must be to all who want it Software must not restrict other software with which it is bundled Program rights are not dependant on other software with which it is bundled With open source software, there is also closed source software. Closed source software is when the source code is not available for modification. Another side of closed source software is that the software has a copyright. There are four basic types of closed source software: Commercial – Software owned by a company or person which is for sale to users. Proprietary – Software which is privately owned, which can include software written for a specific use or company. Freeware – software which is given freely and not allowed to be sold by anyone. Because the source code is not available it cannot be easily modified. Shareware – Same as Freeware, except that the owner asks that the users pay a fee to continue to use the software. Some Shareware can be limited to a trial in some manner. Another type which doesn’t fall into the above categories is “Public Domain”. Public Domain software is software which has not been copyrighted or the copyright has expired. Public Domain software can be used, but it is best not to modify it and release since some legal issues may still come up with the original owner. A final licensing type is the Berkeley System Distribution (BSD) License. The BSD License has two main requirements: No one may take credit for a program they did not write. For example, someone may not redistribute a program and list themselves as the owner. If the software does not work as intended legal action cannot be taken against the owner of the software. It is possible under the BSD License to take the source code and include it in commercial or proprietary software programs. To protect the programmers from losing their intellectual property there was introduced the General Public License (GPL). GPL protects the software from being stolen by anyone and taken over to be made into commercial software. The current version of GPL is version 3 and a general guide can be viewed at https://www.gnu.org/licenses/quick-guide-gplv3.html. Anyone who modifies a program under the GPL license must keep the modified program under the same GPL license; this is referred to as “copyleft”. Some various download sites are as follows: Linux Kernel – www.kernel.org GNU – www.gnu.org FSF - http://www.fsf.org/ GNU Software - http://directory.fsf.org/wiki/GNU Linux can be downloaded from various sites which includes a specific distribution. A Linux distribution, or distro, is a collection of software bundled with the Linux kernel. A few examples are listed: Debian – www.debian.org/distrib/ftplist RedHat – www.redhat.com Slackware – www.slackware.com Fedora – fedoraproject.org SUSE – www.suse.com Puppy – puppylinux.org Ubuntu – www.ubuntu.com The listed distributions are only an example list. A more comprehensive list can be found at: http://en.wikipedia.org/wiki/List_of_Linux_distributions. Again, the list is not a complete list since newer distros are released often and some distros can disappear.