Thursday, May 10, 2012

Basic Concept of Linux and Linux File System Standard

Linux is the joint name of Unix computer operating system. The kernel of Linux operating system is also called Linux. Linux operating system is the most famous one in the development of free software and open source code. Strictly speaking, the word "Linux" itself only stands for Linux kernel. Actually, users are used to using Linux to describe the operating system which is based on Linux kernel and applies data base and all tools of GNU project. Linux was named by computer amateur Linus Torvalds.

Basic Concept of Linux
Simply speaking, Linux is operating system similar to Unix and it is free and it can be spreaded freely. This system is designed and realized by tens of thousands of programmers all over the world. Their purpose is to build a system compatible with Unix, which is not restricted by copyright of commercialized software and used freely all over the world.

Disks and Partitions
A disk can be divided into a primary partition and several extended partitions (logical partitons). And Linux can be installed in any location. Therefore, many machines may have several windows systems and Linux multiple startup.
There is no concept of letter in Linux. All disks are treated same in Linux. There are only layers of directories from boot directory in system. One disk may have many directories, and one directory may cross several disks.

Ext2: Ext2 is standard file system in GNU/Linux.
Ext3: Ext3 is the next generation of Ext2 and it has Ext2 format and log function is added.
Ext4: Ext4 is the subsequent version of Ext3 file system.
Linux swap: It is a swap system specially used to swap partitions in Linux system.
VFAT: VFAT is called long file system, a Linux file system compatible with Windows system, supporting long file name. It can be used as partitions in which Windows and Linux swap files.

Linux File System Standard
/: Boot directory, all directories are started from boot directory in boot directory.
/bin: storing common commands
/boot: guidance for the core program directory
/dev: external device name
/etc: etcetera, system managing the configuration files and subdirectories
/home: storing master directory of /home/ users. Other directories including ftp, httpd, samba and so on.
/lib: library, the basic dynamic link library of system
/lost+ found
/opt: optional
/proc: virtual system, generalized in RAM when system firstly started
/root: a acquiescent master directory of superuser  
/sbin: system supervisor used by system administrator
/tem: storing temporary files generalized in program execution.
/usr: a directory taking largest space, containing almost all application programs and files of users.
/var: storing system record files and configuration files.

Linux history is closely connected to GNU.
1983, Richard Stallman built GNU Project. The target of this project is to develop a totally free and unconstrained Unix-Like operating system. When the project was organized in 1990, GNU began to produce or collect all kinds of necessary components such as libraries, compilers, debuggers, text editors, web server and a Unix shell, except that the kernel was still wanted. In 1990, GNU planed to develop system kernel on the framework of Mach microkernel, which is called GNU Hurd. Because the design of Mach was very complicated, the progress was relatively slow.
In the original assumption, Linux was an operating system similar to Minix. In April, 1991, a student of University of Helsinki in Finland, named Linus Benedict Torvalds (the most famous programmer and hacker in the world) was not satisfied with the teaching operating system Minix. So he designed a system kernel Linux 0.01 on the basis of MINIX which could be used in low-end machine. But he did not use any MINIX or UNIX source code. He announced through the USENET that Linux was a free system mainly used in x86. He hoped everybody to perfect it and he put the source code on FTP of Finland for free download. At first, he wanted to call the system "Freax", a combination of "free" and "freak" and the commonly used letter "X" was attached to correspond to the Unix-like system. However, staffs of FTP thought "freax" was not good and used the subdirectory Linux for storage, so the system is called "Linux". And this Linux only contained kernel program and 10,000 lines of code, and it had to run on the basis of Minix operating system and boot from hard disk. So it was not a complete system. Then the second version(version 0.02) was released in October and Linus Benedict Torvalds published an information on comp.os.minix:
  Hello everybody out there using minix-
  I'm doing a (free) operating system (just a hobby,
Won't be big and professional like gnu
) for 386(486) AT clones.
As many professional users (programmers mainly) voluntarily developed the application programs, and they were amended by many people through the internet. Therefore, its surrounding programs became more and more and Linux gradually expanded.
Since 1983, GNU project had been devoted to develop a free and integrated Unix-like operating system including software development tools and varieties of application programs. When Linux kernel is released in 1991, GNU had finished development of all necessary softwares except kernel system. In the efforts of Linus Torvalds and other developers, GNU components could run on the Linux kernel. The kernel was based on GPL (GNU General Public License) but Linux Kernel was not a part of GNU project. In March, 1994, Linux 1.0 was officially released. And Mar Ewing built Rat Hat software company, becoming the one of most famous distributors of Linux.
The Historical Origin of Unix andLinux
LILO(Linux Loader)is used in boot loader in early Linux. It has intolerant defects, for example, it can only recognize hard disk of 8G. Then GRUB (GRand Unified Bootloader) is added and it abandons those defeats. It has the function of searching core files dynamically. When users starting system, they can edit boot system files. Then Linux kernel is loaded in files system through ext2 or ext3.
The symbol and mascot of Linux is a penguin named Tux. Because Linus was once bitten by a penguin in the zoo in Australia, he chose penguin as symbol of Linux. Registered trademark of Linux belongs to Linux. In 1996, a lawyer named William R. Della Croce sent letters to every publishers of Linux to claim that he had the ownership of Linux trademark and asked the publishers to pay copyright royalty. And those publishers appealed collectively and asked that the registered trademark be reallocated to Linus Torvalds. And Linus Torvalds declared time and again that Linux was free and he could sell it him self, but Linux must not be sold.
Some versions of Linux need not to install. They can be applied through CD or bootable USB storage device. So they are called LiveCD.
Features of Linux

Linux Kernel
Amounts of GNU softwares (shell program, tools, program libraries, editors and tools and some other programs such as Emacs) are applied in most of operating system based on Linux kernel. Therefore, the pathfinder of GNU project Professor Richard Stallman proposed renaming Linux operating system as GNU/Linux. But some people only call the operating system Linux.


Basic Thought
There are two basic thoughts in Linux: firstly, every thing is file,and secondly, every soft ware has specific usage. The detailed mean of the first is that all things in system are considered as files. Commands, hardwares and softwares, operating systems and processes are considered as files with respective features or types by the kernel of operating system. As to the statement that Linux is based on Unix, it is because that the basic thoughts of these are very similar to each other. Generally speaking, Linux has the following features:
1. Inexpensiveness
Because of its inexpensiveness and adjustability of length, Linux is usually applied in embeded system such as STB (Set Top Box), mobile phones and mobile devices.
2. Universality
The number of supercomputers adopting Linux becomes larger and larger. According to the list of top 500 supercomputers in November, 2005,the most fast two groups of supercomputers both adopted Linux.
3. Flexibility
Linux is famous for its high efficiency and flexible. It can realize all features of Unix in PC and is has functions of multitask and multiuser.
4. Reason for Its Extreme Popular
There are two reasons for its extreme popular. One is that it is a free software and users can obtain it and its source code without payment, and edit it according to their demands and use and spread it freely. The other reason is that it has all features of Unix. Anyone who wants to use or learn to use Unix operating system can be benefited from Linux.


Improvement
Revised several times (including the update of kernel and perfection of surrounding programs ), Linux has became a multiplex operating system of 32 bits, which abides by POSIX standard. And the version of 6+4bits is in development.

Supported Partition magic
MiniTool Partition Wizard is partition magic software that supports Linux operating system. It is in support of the size adjustment, remove, and establishment and deletion operation of Ext2, Ext 3 and Linux swap file system in Linux operating system. Meanwhile, it contains boot loader MiniTool Partition Wizard Bootable CD which is built in Linux. Even the current system can not run normally, software can be applied by using MiniTool Partition Wizard Bootable CD to realize relative partition management and operation,without unload the current disk. 

For more information: http://www.data-recovery-app.com

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