Learn Linux Operating System

 Learn Linux Operating System

 

Linux is a family of free and open-source software operating systems based on the Linux kernel, an operating system kernel first released on September 17, by Linus Torvalds.

And also, Linux is a command line interface, used by most large, powerful computers and it is very popular and very easy to find information and get help. It is very staple - computers running Linux almost never crash. It’s very efficient which can smoothly manage extremely huge amounts of data. Most new bioinformatics software is created for Linux - it’s easy for the programmers.

 

Linux Operating System (OS) is a resource manager. It takes the form of a set of software routines that allow users and application programs to access system resources (e.g. the CPU, memory, disks, modems, printers’ network cards etc.) in safe, efficient and abstract way.

Linux is a layered operating system. Its innermost layer is the hardware that provides the services for the OS.

The operating system, referred to in Linux is the Kernel, which interacts directly with the hardware and provides the services to the user programs. These user programs don’t need to know anything about the hardware. They just need to know how to interact with the Kernel and its up to the Kernel to provide the desired service.The kernel is the core of the Linux operating system which schedules processes and interface directly with the hardware. It manages system and user I/O, processes, devices, files, and memory.

The kernel provides low-level device, memory and processor management functions (e.g. dealing interrupts from hardware devices, sharing the processor among multiple programs, allocating memory for programs etc.)

 

Linux is multi-user, multi-tasking operating system. You can have many users logged into a system simultaneously, each running many programs. It is the duty of the kernel to keep each process and user separate and to regulate access to system hardware, including cpu, memory, disk and other I/O devices 

 

`Classification of UNIX/Linux

UNIX is a Multi-User/Multi-Tasking operating system

and exists in many different versions (“derives”):

Solaris, AIX, XENIX, HP-UX, SINIX, Linux.

Operating system (OS): Sum up of all programs which are required to operate a computer and which control and monitor the application programs.

 

Essential features of Linux/Unix

• has been originally written in the programming language C, and is therefore a classical        platform C-programs. UNIX contains well suited environments for program development (C, C++, Java, Fortran, ...).

 

• is mainly used for scientific-technical applications on mainframes and workstations, but has become, because of Linux, also popular for classical-applications throughout the last years.

 

• is perfectly suited for application in networks. Larger systems and networks require an              administrator.

 

• offers various alternatives for the solution of most tasks. The multitudes of commands (more than in any other OS) are brief and flexible.

 

• is originally command-line oriented, but can be used via a graphical user interface (X Window

system).

 

Graphical user interface

 

Originally, UNIX is command-line oriented. The X Window system enables convenient interaction via a window-oriented graphical interface, similar to other OS.The window manager is responsible for the management and display of the individual windows. Each window manager (and there are a variety of such managers) can be distinguished by its own Look and Feel (appearance of window decorations and control devices etc.). Most window managers can be chosen at the login-menu. Examples for simple window managers:

• twm: very simple and resource-saving

• mwm: Motif window manager, more common and more advanced

• xfce: convenient, simple, and resource-saving(recommended for use in virtual machines)

Moreover, almost all Linux distributions provide graphical desktop environments such as KDE or GNOME, which have a functionality far beyond simple window managers.5 command xterm Syntax: xterm [options]Though there is a graphical interface, UNIX needs the possibility for direct command input for practical use. Therefore, at least one terminal window needs to be open. This can be accomplished via the window manager or the desktop environment (‘console’)

 More windows can then be opened with the command xterm .Generally, all UNIX commands have a variety of op-tions, which usually begin with -. For the most important commands which will be introduced in the following such as, for example: wegner@arber:~ > xterm -geo 80x40 -fn 10x20The command xterm is called with two options -geo,-fn, which, in this case, need a3.

 

 File systems

 

Logics, file types

“In UNIX everything is a file.”

The following file-system objects can be found

• ‘normal’ (text-) files

• executable files (binary files or shell scripts)

• directories

• device files

• pipes

• symbolic or hard links (references to files)

All files and file system objects are ordered within a hierarchical file tree with exactly one root directory‘/’.

In contrast to the MS-Windows file system, the UNIX file system does not distinguish between different drives. All physical devices (hard disks, DVD, CDROM, USB, floppy) are denoted by specific files inside a certain directory within the file tree (usually within /dev). File names consist of a sequence of letters, digits and certain special characters, and must not contain

slashes (for convenience, they should neither contain empty spaces).Avoid characters which might be interpreted by the shell in a special way. A file can be referenced within the file tree by either an absolute or a relative path name. An absolute path name consists of all directories leading to the file and the file name, and always begins with a / (the root directory).

In many shells and application programs, the tilde denotes the home directory. Command pwd

Syntax:pwd displays the current directory. Example: wegner@arber:~ > pwd /home/wegner

wegner@arber:~ >dditional arguments (width and height of window, font name & size).

 

 

 

In conclusion, from smartphones to cars, super computers and home appliances, the Linux operating system is everywhere. Linux is the best-known and most-used open source operating system. As an operating system, Linux is software that sits underneath all of the other software on the computer, receiving request from those programs and relaying these requests to the computer’s hardware.