UNIX: Introduction to Beginners

What is UNIX? 

UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs which make the computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.

UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session.

Types of UNIX :-

There are many different versions of UNIX, although they share common similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X.

Here in the School, we use Solaris on our servers and workstations, and Fedora Linux on the servers and desktop PCs.

The UNIX operating system:-

The UNIX operating system is made up of three parts; the kernel, the shell and the programs. 

The kernel:

The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to system calls.
As an illustration of the way that the shell and the kernel work together, suppose a user types rm myfile (which has the effect of removing the file myfile). The shell searches the filestore for the file containing the program rm, and then requests the kernel, through system calls, to execute the program rm on myfile. When the process rm myfile has finished running, the shell then returns the UNIX prompt % to the user, indicating that it is waiting for further commands.

10 Open Source Tools For Building Scalable Web Applications!

When you're designing a web application, scalability and performance are very important. Every developer must take these two steps into consideration before building their application. To do this effectively, you need the best tools. Here are 10 of the most popular ones.

1. Apache HTTP Server: Extensible, fast and highly scalable. These are the qualities of the Apache HTTP server that make it immensely popular. Of course, there are other features too.

2. Tomcat: This open source software holds configuration and management tool. While the Apache Tomcat tool is an implementation of Java, it can also be configured using configuration files from XML. You can use it to implement JSP along with Java servlet specifications.

3. Modsecurity: This is a web application firewall that can be embedded into the web server infrastructure. It is also amongst the top available open source WAF solutions.

4. Memcached: This is an open source distributed caching system that is generic in nature. It has a simple design and delivers very good performance.

5. Varnish: This is a web application accelerator or HTTP reverse proxy. It is a very high speed software that can speed up the process delivery immensely.

What is NAGIOS ?

Nagios is a system and network monitoring application. It watches hosts and services that you specify,alerting you when things go bad and when they get better. Nagios was originally designed to run under Linux, although it should work under most other unices as well. 
                                                                                                                           Nagios is licensed under the terms of the GNU General Public License Version 2 as published by the Free Software Foundation. This gives you legal permission to copy, distribute and/or modify it under certain conditions.

Some of the many Features of Nagios include:

1) Monitoring of network services (SMTP, POP3, HTTP, NNTP, PING, etc.)

2) Monitoring of host resources (processor load, disk usage, etc.)

3) Simple plugin design that allows users to easily develop their own service checks.

4) Parallelized service checks.

4) Ability to define network host hierarchy using "parent" hosts, allowing detection of and 
     distinction between hosts that are down and those that are unreachable.

5) Contact notifications when service or host problems occur and get resolved (via email,  
    pager, or user-defined method) .

6) Ability to define event handlers to be run during service or host events for proactive 
     problem resolution.

7) Automatic log file rotation.

8) Support for implementing redundant monitoring hosts.

9) Optional web interface for viewing current network status, notification and problem 
     history, log file, etc.

System Requirements : 

                            The only requirement of running Nagios is a machine running Linux (or UNIX variant) and a C compiler. You will probably also want to have TCP/IP configured, as most service checks will be performed over the network. 
                                 You are not required to use the CGIs included with Nagios. However, if you do decide to use them, you will need to have the following software installed...

1) A web server (preferrably Apache).

2) Thomas Boutell’s gd library version 1.6.3 or higher (required by the statusmap and
      trends CGIs)


Downloading The Latest Version

You can check for new versions of Nagios at http://www.nagios.org.

Nano Linux.. ! A very tiny Linux distribution with GUI,,, SIZE UPTO approx 14 MB

Nanolinux is a very tiny Linux distribution based on MicroCore Linux with busybox.

It uses Nano-X instead of X11. FLTK 1.3.x is used as the GUI toolkit. The window manager is SLWM.

The following applications are included:

1) Dillo browser.

2) FlWriter text processing program.
 
3) Sprsht spread sheet program.

4) FLTDJ personal information manager.

5) Antipaint paint program.

6) Fluff file manager.
 
7) NXterm terminal emulator.

8) Flcalc calculator.

9) FlView image viewer.

10) Fleditor.

11) Games: Tuxchess, NXeyes, Checkers, Blocks, Mastermind.

12) Truetype fonts, UTF08 support.

7 Facts About CentOS That You Should Know

What do you do when you want to use Red Hat Enterprise Linux (RHEL) without paying for it? The answer is simple, you use CentOS. This is a Linux distribution that is derived from RHEL, but is available for free. But, while this distro is available for free, you have to sacrifice on some aspects. One of these is the fact that the CentOS team doesn’t offer any support services. Still, CentOS is amongst the most popular Linux distros today, which makes these facts about the OS all that more important to know. If you’re going to choose a distro for your projects, then you might as well know as much as possible about it.

1. The CentOS team, which makes this repackaged version of RHEL, is a volunteer group. The team takes the source packages from RHEL that are publicly available and repackages them into binaries. They distribute this software through public mirrors and Red Hat itself has no partnership with CentOS. 

2. No Support: This is actually quite surprising for a popular Linux distro. While CentOS has been used commercially by many companies, no support is provided by the team yet. So, you’re basically depending on IT consultants for support purposes.

3. Major releases come a little later: The time difference between the release of a major version for RHEL and CentOS has been increased considerably over the years.

4. Catching up to Red Hat: Being what it is, CentOS can not overtake Red Hat. This is because the team always has to wait for the company to release the packages before it can repackage them. So, if there is a critical security issue that has been discovered, RHEL will get the solution much faster than CentOS.

9 Ways To Sort Files In Linux Environment

Sorting files is important for meaningful output and is useful while dealing with DB files, CSV, xls, log files and text files. By default, the sort command will sort according to alpha-bates, sorting according to single character vertically. If it finds the same character in two lines, then it will move on to sort the second character.

There are 9 ways to do that according to www.linuxnix.com. You can mix and match them as per your requirement.

• 1:To sorting file names according to alpha-bates: sort filename.txt.

• 2: If you have a file with host names in the third column, to sort it according to the column, use K for sorting that. Like, sort k3 filename.txt.

• 3: To sort/ etc/password file according to home directories, sort will by default take space/tabs as field separators. In etc/passwd file, the field separator is : and this can be done with t option. sort -t: -k6 /etc/passwd 

• 4: To sort according to number, etc/passwd file according to UID, use -n option to do that. Sort will not understand numbers by default, so, use -n to make sure sort command understands it.sort -n -t: -k3 /etc/passwd. Without -n option sort will by default sort only first numerical char. 

Top 12 Linux Distros And Their Usage

While many would argue that the list is not complete but we have tried to bring to you some of the key Linux distros. That's not it. This article also helps you determine the best distro that suits your need.
          Let's analyse certain major Linux distros and their anticipated purpose:

1) Ubuntu: Ubuntu was once considered as the standard Linux distribution for beginners, but due to Ubuntu Unity, that title no longer belongs to Ubuntu, but that doesn’t mean it is useless. Very soon, Ubuntu is likely to emerge with the first trustworthy Linux tablet

2) Linux Mint: This is the effective standard for beginners. Linux Mint introduced great and user friendly features in Ubuntu and enhanced GNOME 3- a combination that provided an incredible environment for beginners as well as old users of Linux.

3) Fedora: If you want an advanced version of Linux, go for Fedora. Even those, looking for pure take on GNOME 3, opt for Fedora.