LINUX THE GREAT

           “The most unfortunate thing is that India still seems to believe in proprietary solutions. In India, open source code software will have to come and stay in a big way for the benefit of our billion people.”                                                                                                                                                     —Our Ex-President Dr.APJ Abdul Kalam 

                             
                                 LINUX

             
                                 Linux is a free Unix-type operating system originally created by Linus Torvalds with the assistance of developers around the world. Developed under the GNU General Public License , the source code for Linux is freely available to everyone.

              
Richard Matthew Stallman
 (Founder of GNU)

                      Here ‘FREE’ means not only the free of cost, actually it gives 4 freedoms
       
    # The Freedom to Use
    # The Freedom to Modify
    # The Freedom to Copy
    # The Freedom to Redistribute Changes
 
Linus Torvalds
(Inventor of Linux Kernel)

                        Why we need Linux?

    # Freedom
    # Virus free
    # Stability & Security
    # Multi-user
    # Installing Softwares becomes In SINGLE-CLICK
    # No PROPRIETARY issues
    # Don’t wait years to fix the bugs
    # It can run for years without restarting
    # Jump in to Next generation of computers
    # Do something for world
    # An excellent window system called X
    # Supports multiple processors as standard
    # True multi-tasking
    # You can try Linux without touching the OS which already you have
    # Get great music players
    # Play hundreds of games for free
    # Last but not least Enjoy free and unlimited support

             How can we get Linux ?

    # By downloadind from corresponding site
    # By getting the CDs from your city
    # By asking CDs through mail

                   What are all have Linux?

   Here I mentioning few

(1) Server Side
   
     # DNS Server      –    BindDNS
     # Mail Server       –    Postfix
     # Web Server     –    Apache
     # DB Server        –    Mysql
     # File Server       –    NFS & Samba
     # Print Server     –    CUPS
     # Firewall            –        IPTABLES
     # Proxy Server   –    Squid
       and many more…..

(2) Development Side
  
    # GUI related
            * X Window System
            * GNOME
            * KDE
            * Xfce desktop environments
    # OpenOffice.org for office suite
    # Mozilla for Firefox for web browsers
    # Thunderbird email client.
    # Typesetting and document preparation systems
        * TeX
        * LaTeX
    # Graphics tools
        * GIMP raster image editor
        * Inkscape vector graphic editor
        * Paint.NET raster drawing program
        * Blender 3D animation program
    # Text editors like vi or emacs.


          Some Linux Distributions

   

    # Debain based distros like ubuntu

    # Redhat based distros like fedora,centos
          
    # Mandriva based distros like mandrake

              LUG (Linux User Group)

                      A Linux User Group or Linux Users’ Group (LUG) is a private, generally non-profit or not-for-profit organization that provides support and/or education for Linux users, particularly for inexperienced users.
   
  For our city  it is ilugc , which is doing some great works here.

Intruders hacked my PC

Last week I have got a bad/great experience.
I installed RHEL5 last week with static iP.

some one has entered in my system from these ips
82.79.161.104,92.80.199.219,79.113.9.116
and they created a user with uid of 0(zero)
and done nasty things like crashing the system.

I found this by giving ‘last’ command .
which shows me unknown ip has logged in my system.
Then i check the /etc/passwd file
which shows a user named with “girgo” with uid of 0 has created.

I think my root password should be the problem
admin123) which is a dict word
and crackers has done their job easily.

They create a user named “oracle”
and they create a directory named ” bot “
and some files and some scripts

I shamed since i am one of the victim.
I think this will be the lesson for everyone.

Lesson Learned :

1)Password should be strong.
2)Allow ssh from known ips only.
3)Have to take bare metal backup after installing the system , for quick restore
4)Install and monitor any intrusion detection system

Clearing last logins and history

We can clear the history command’s history by simply executing history -c

We can clear the last command’s history by executing > /var/log/wtmp

This command will delete all informations about last logins

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Adding sudo users

We are all know that we don’t login as root user.
But we have to do administrative works.
sudo command will do that.
In Debian Based Distros the first user will be the sudo User.
Suppose we want to add new users with sudo permission, then add that user in /etc/sudoers

It can be done as follows

#visudo
add the user name in that file
say i want to add user1 as sudo previlege then add user1 ALL=(ALL) ALL

Now the user1 can do the administrative works with his password only (no need to know the root password)

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To Change the default editor for crontab

In Ubuntu the default editor for crontab is Nano.

we can change this by executing the following  command:

i.e. sudo update-alternatives –config editor

After executing  this command we can see like this

There are 4 alternatives which provide `editor’.

Selection    Alternative
———————————————–
1    /usr/bin/vim.tiny
2    /bin/ed
*+        3    /bin/nano
4    /usr/bin/vim.basic

Press enter to keep the default[*], or type selection number: 1

Now we can select the editor by just typing the corresponding number.

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