Thursday, 27 October 2011

LINUX NETWORKING

LINUX SUPPORTS MANY DIFFERENT NETWORKING PROTOCOLS SUCH AS :
  • TCP/IP
  • UDP/IP
  • IPX/SPX
  • APPLETALK
  • DLC
  • DECNET
NETWORK COMMAND
  1. ifconfig : Configure a network configure the kernel resident network interfaces. It is used at boot time to set up interfaces as necessary.
  2. dhclient : This script is used by the dhcp client to set each interface's initial configuration prior to requesting an address, to test the address once it has been offered, and to set the interface's final configuration once a lease has been acquired.
  3. ping : is a computer network administration utility used to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer

LiNuX SeRvICeS & cOnFiGuRaTiOn

Vi Editor

What is vi?

The default editor that comes with the UNIX operating system is called vi (visual editor). [Alternate editors for UNIX environments include pico and emacs, a product of GNU.]

The UNIX vi editor is a full screen editor and has two modes of operation:

Command mode commands which cause action to be taken on the file, and

Insert mode in which entered text is inserted into the file.

In the command mode, every character typed is a command that does something to the text file being edited; a character typed in the command mode may even cause the vi editor to enter the insert mode. In the insert mode, every character typed is added to the text in the file; pressing the <Esc> (Escape) key turns off the Insert mode.

While there are a number of vi commands, just a handful of these is usually sufficient for beginning vi users. To assist such users, this Web page contains a sampling of basic vi commands. The most basic and useful commands are marked with an asterisk (* or star) in the tables below. With practice, these commands should become automatic.

NOTE: Both UNIX and vi are case-sensitive. Be sure not to use a capital letter in place of a lowercase letter; the results will not be what you expect.



To Get Into and Out Of vi

To Start vi
To use vi on a file, type in vi filename. If the file named filename exists, then the first page (or screen) of the file will be displayed; if the file does not exist, then an empty file and screen are created into which you may enter text.

* vi filename - edit filename starting at line 1
  vi -r filename - recover filename that was being edited when system crashed


Inserting or Adding Text
The following commands allow you to insert and add text. Each of these commands puts the vi editor into insert mode; thus, the <Esc> key must be pressed to terminate the entry of text and to put the vi editor back into command mode.

* i - insert text before cursor, until <Esc> hit
   I - insert text at beginning of current line, until <Esc>hit
* a - append text after cursor, until <Esc>hit
  A - append text to end of current line, until <Esc>hit

Moving the Cursor
Unlike many of the PC and MacIntosh editors, the mouse does not move the cursor within the vi editor screen (or window). You must use the the key commands listed below. On some UNIX platforms, the arrow keys may be used as well; however, since vi was designed with the Qwerty keyboard (containing no arrow keys) in mind, the arrow keys sometimes produce strange effects in vi and should be avoided.
If you go back and forth between a PC environment and a UNIX environment, you may find that this dissimilarity in methods for cursor movement is the most frustrating difference between the two.
In the table below, the symbol ^ before a letter means that the <Ctrl> key should be held down while the letter key is pressed.

* j or <Return> [or down-arrow] - move cursor down one line
* k [or up-arrow] - move cursor up one line
* h or<Backspace> [or left-arrow] - move cursor left one character.
* l or<space> [or right-arrow] - move cursor right one character.

Changing Text
The following commands allow you to modify text.

   cw - change the current word with new text,starting with the character under cursor, until <Esc> hit.
   cc - change (replace) the entire current line, stopping when <Esc> is hit.
    c  - change (replace) the characters in the current line, until <Esc> hit.
    R - replace characters, starting with current cursor position, until <Esc> hit.


Deleting Text
The following commands allow you to delete text.

*  x - delete single character under cursor.
*  d - delete entire current line.
   D - delete the remainder of the line, starting with current cursor position.
 dw - delete the single word beginning with character under cursor.

Cutting and Pasting Text
The following commands allow you to copy and paste text.

  yy - copy (yank, cut) the current line into the buffer.
 yw - copy forward one word.
    p - put (paste) the line(s) in the buffer into the text after the current line.

To Save and Exit vi
Usually the new or modified file is saved when you leave vi. However, it is also possible to quit vi without saving the file.
Note: The cursor moves to bottom of screen whenever a colon (:) is typed. This type of command is completed by hitting the <Return> (or <Enter>) key.

   Esc + shift
: w<Return> - write current contents to file named in original vi call.
: q<Return> - quit ( or exit ) vi
: wq<Return> - quit vi, writing out modified file to file named in original invocation.



Wednesday, 26 October 2011

Types of Shells

Bourne Shell

 C Shell

TC Shell
 

 Korn Shell

Almquist Shell

Z Shell

Command function in the Linux

THE BASIC COMMAND FUNCTION


 
 
 

Permission Command

PERMISSION COMMAND
Permission Diagram

Use Chmod to change file permission

Use Chown to change user ownership

Use Chgrp to change group ownership




All About Ubuntu


what iS UBUNTU?

Ubuntu is an operating system that is developed by a worldwide community of programmers as well as by employees of Ubuntu's commercial sponsor, Canonical. Ubuntu is based on the concept of free or open-source software, meaning that you do not pay any licensing fees for Ubuntu, and you can download, use, and share the operating system free of charge.


Being a Linux-based operating system, Ubuntu has a well-deserved reputation for stability and security. Historically, Linux has proven itself to be a workhorse server operating system, and this is where, up until now, it has been most widely used and best known. As of June, 2007, 78 percent of the world's top 500 supercomputers were running Linux, according to Top500.org.


However, in recent years, Linux has also become viable on desktop and laptop computers, making it an option for individuals and businesses. Ubuntu is generally acknowledged to be the most widely used version of Linux available, and Mark Shuttleworth, the founder and CEO of Canonical, estimates Ubuntu has between six and eight million users. Because the software is free to download and share, it is difficult to track exact usage numbers.




UBUNTU VERSUS WINDOWS AND OS X

How does Ubuntu compare to the two best-known operating systems — Microsoft Windows and Apple OS X? The most obvious way is in the licensing and distribution terms. Ubuntu is "free software" — a term which is often misunderstood to mean only free of cost. 


While Ubuntu is free of cost, the term "free software" more accurately refers to the freedom to run the program for any purpose, to study how the program works and modify it to your needs, to redistribute copies, and to improve the program and release your improvements to the public (see the Free Software Foundation's Web site for a detailed definition).


Ubuntu also includes many of the programs used for everyday computing at no cost, unlike Windows and OS X. Some examples are:
  • Office Suite: OpenOffice.org, a full office suite with a word processor, spreadsheet, and presentation software that can read and write in .doc, .xls, and .ppt formats and can also output to PDF, and supports the ISO standard for electronic office documents,Open Document Format. (Free training for OpenOffice.org is available at LearnFree.org.)
  • Desktop Email Client: Evolution, an email program with a similar interface to Microsoft Outlook.
  • Web Browser: Firefox, the increasingly popular Web browser.
  • Databases: The two best-known open-source databases on Linux are PostgreSQL and MySQL, but commercial databases such asOracle and IBM's DB2 are also available. There are also tools like Glom that provide an easy-to-use graphical interface for designing and editing databases.
  • Others: Ubuntu's online Applications Guide lists some Ubuntu-compatible applications that allow you to edit images, listen to and manage music, edit and watch videos, read PDFs, connect to instant messaging services from MSN, AOL, Google, Yahoo, and more.
  • Updates and bug fixes: Security updates and bug fixes for applications and the operating system are managed by Ubuntu, and users are notified about these updates through an icon in the taskbar, which they can click on to install. (Note that you must be connected to the Internet to receive these notices.)