How to Install CentOS 6.x Linux (only CLI mode)

CentOS 6.x Linux for Servers & Desktops

 Step by step guide to on how to install CentOS 6.x Linux in a new machine(or formatted old PC), the type install is minimal/typical which is perfect for servers, no Graphical User Interface(GUI) will be installed . This is how I install all of our Linux servers in office, you can use this user guide can also be used to install Redhat Enterprise on desktop or laptops.

Step-1-Download ISO file and burn it to DVD
Visit http://centos.org and download the install ISO image(s) for your servers architecture (i686, x86_64 etc). I would recommend the torrent option of downloading the CD / DVD images for  faster download.

After finishing the download then create iso to dvd using nero burner or others

Step-2-boot from DVD
Swith on and go to BIOS setup for change boot device to cd/dvd. INSERT the CentOS IN DVD ROM then restart and wait

Download details of CentOS

Download details of CentOS

CentOS is an Enterprise-class Linux Distribution derived from sources freely provided to the public by a prominent North American Enterprise Linux vendor.  CentOS conforms fully with the upstream vendor's redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes packages to remove upstream vendor branding and artwork.)  CentOS is free.

Wiki for CentOS

CentOS Download Information

CentOS Public Mirror List

Direct Mirror list for 6.3

What is CentOS?

Basically if you want to learn Red Hat, you can download CentOS for free. You can download RHEL source for free, but unless you want to spend weeks building it, I suggest you download CentOS instead. CentOS is built from the RHEL source, and only the trademarks (logos) have been replaced.

CentOS 

CentOS (Community Enterprise Operating System) is a Linux distribution which attempts to provide a free enterprise class computing platform which has 100% binary compatibility with its upstream source, Red Hat Enterprise Linux (RHEL)

RHEL is available only through a paid subscription service that provides access to software updates and varying levels of technical support. The product is largely composed of software packages distributed under free software licenses and the source code for these packages is made public by Red Hat.

CentOS developers use Red Hat's source code to create a final product very similar to RHEL. Red Hat's branding and logos are changed because Red Hat does not allow them to be redistributed.

CentOS is available free of charge. Technical support is primarily provided by the community via official mailing lists, web forums, and chat rooms. The project is not affiliated with Red Hat thus receives no financial or logistical support from the company; instead, the CentOS Project relies on donations from users and organizational sponsors.

Details- http://www.centos.org/

Where can we download Redhat Enterprise 6.X

Where can we download Redhat Enterprise 6.X

Without paying money, you can only get the SRPMs RPMs (Redhat Package Management) for RHEL6.x.
Link- ftp://ftp.redhat.com/redhat/linux/enterprise/6Server/en/os/SRPMS/


Documentation about REDHAT / RHEL - from this link 

Redhat/RHEL download link - Torrent

Basically if you want to learn Red Hat, you can download CentOS for free. You can download RHEL source for free, but unless you want to spend weeks building it, I suggest you download CentOS instead. CentOS is built from the RHEL source, and only the trademarks (logos) have been replaced.

Details please visit - PCPATSHALA

Graphical User Interface

In computing,Graphical User Interface (GUI, pronounced 'gooey') is a type of user interface that allows users to interact with electronic devices using images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances, office, and industry equipment. A GUI represents the information and actions available to a user through graphical icons and visual indicators such as secondary notation, as opposed to text-based interfaces, typed command labels or text navigation. The actions are usually performed through direct manipulation of the graphical elements.

The term GUI is restricted to the scope of two-dimensional display screens with display resolutions able to describe generic information, in the tradition of the computer science research at the PARC (Palo Alto Research Center). The term GUI is rarely applied to other low-resolution types of interfaces that are non-generic, such as video games

For more information please visit - PCPATSHALA

Ease

Although new users may have a difficult time learning to use the mouse and all GUI features, most users pick up this interface much easier when compared to a command line interface.

Control

Although a GUI offers plenty of control of a file system and operating system, the more advanced tasks may still need a command line.

Multitasking

GUI users have windows that enable a user to view, control, and manipulate multiple things at once and is much faster to navigate when compared with a command line.

Speed

A GUI may be easier to use because of the mouse. However, using a mouse and keyboard to navigate and control your operating system for many things is going to be much slower than someone who is working in a command line.

Scripting

Although A GUI enables a user to create shortcuts, tasks, or other similar actions, it doesn't even come close in comparison to what is available through a command line.

Remote access

Although remote graphical access is possible. Not all computers and especially not all network equipment will have this ability.

For more information please visit - PCPATSHALA

Command-Line Interface (CLI)

A command-line interface (CLI) is a means of interaction with a computer program where the user (or client) issues commands to the program in the form of successive lines of text (command lines).The CLI was the primary means of human interaction with most early operating systems, including MS-DOS, CP/M, Unix, and Apple DOS. The interface is usually implemented with a command line shell, which is a program that accepts commands as text input and converts commands to appropriate operating system functions.

Ease 

Because of the memorization and familiarity needed to operate a command line interface, new users have a difficult time navigating and operating a command line interface.

Control

Users have much more control of their file system and operating system in a command line interface. For example, users can copy a specific file from one location to another with a one-line command.

Multitasking

Although many command line environments are capable of multitasking, they do not offer the same ease and ability to view multiple things at once on one screen.

Speed

Command line users only need to use their keyboards to navigate a command line interface and often only need to execute a few lines to perform a task.

Resources

A computer that is only using the command line takes a lot less of the computers system resources than a GUI.

Scripting

A command line interface enables a user to script a sequence of commands to perform a task or execute a program.

Remote access

When accessing another computer or networking device over a network, a user will only be able to manipulate the device or its files using a command line interface.

Advantages of CLI:

= Most folks that have computer technology as a career are familiar with using this interface, especially if they have a *nix background.
= Requires a lower threshold for the interface. This means that a relatively simple program like telnet (available almost on all machines) is all you need to interface via CLI.
= Easy to integrate with scripting, and other programmatic interfaces.
= They can be quite powerful in the right hands. Piping multiple commands together, parsing feedback, etc.
= Many of the most common CLI executables in the *nix world are consistently ported, so there is a lot of consistency across systems.

Disadvantages of CLI:

= Not intuitive, especially to a lay user.
= No media.
= Complex combinations can be difficult to remember, and slower to type (but that is on a task by task basis, as often you can perform tasks faster with CLI)

Sendmail on Centos 5.x

How to install sendmail onCentOs 5.5??

Installation:
Normally, Sendmail (MTA) comes with Centos5.x. But if you cannot find sendmail install on your server
you can donwload the package from

http://www.sendmail.org/releases
.

After finishing the installation of sendmail in centos
You can check the sendmail status by following commands

#sendmail status - [give the sendmail current status]
#sendmail stop - [stop sendmail]
#sendmail start - [start sendmail]
#sendmail restart- [restart sendmail]

Sendmail basic configurations.

#cd /etc/mail
#cp sendmail.mc sendmail.mc.org [copy and store the original configuration file]

#vi sendmail.mc

We have to do 4/5 modifications to sendmmail.mc

Step-1.
dnl define(`SMART_HOST', `smtp.your.provider')dnl

change to
define(`SMART_HOST', `your service provider')dnl

There are more modifications to be done in sendmal.mc,
however if you made this modification correct,
you can rout mails through your smart host.

After you done the change you can save and quit. (:x :wq)

Ten, you have to compile the sendmail.mc to sendmail.cf to do that,

#cd /etc/mail

#m4 sendmail.mc > sendmail.cf

#service sendmail restart

now you can test your sendmail (MTA)

command,

sendmail -v yourmal@urdomain.com
this is test mail
.

you can check the mail log using

tail -f /var/log/maillog

If want to check the MTA functions locally, create local few local mail accounts. Then you can check there mail boxes.

#

LINUX root Password recovery

যদি কেউ Linux root password ভুলে যায়
>> Switch on your PC/Laptop
>> Select the label of Linux then Press e for edit
>>  Select the "kernel..........." and press e again
>> Press on  Space bar 1 or s for Enter
>> Now press b for boot
>>  sh-x.xx#
now you can  change your password by passwd command

For  details about Linux please see pcpatshala