Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
In this article, we will learn how to configure OpenVPN server on Ubuntu Linux. Yes, we can do it using a VPN (Virtual Private network) which allows you to connect to work place from untrusted networks privately and securely. For instance, If you are in a hotel or a coffee shop and wish to access work environment safely and securedly through a Wi-fi network using a Smartphone or laptopOpenVPN is a full featured and open source secure socket layer (SSL) VPN solution that accommodates wide range of configurations.Installing OpenVPNTo start the installation, we needed an Ubuntu machine with non-root user ... Read More
This article will be helpful if we forget the root password on Centos 7.x or RHEL 7.x. In the previous version of RHEL, we can easily break the root password, as by default SE-Linux is enabled. Also note that, RHEL has brought many special new features.Resting the Root PasswordReboot/Restart the system.Press ‘e‘ at the grub boot menu to edit the default boot menu.This screen looks like this for RHEL 7.x –Press us thr down arrow key to find the line which contains similar to the ‘linux16 …… rhgb quit …..” and replace the ‘rhgb quiet’ words with ‘init=/bin/bash’. Once we ... Read More
In this article, we will learn how to configure and install the most popular open source MTA (Mail Transfer Agent) Postfix, which can be used to route email delivery of the Linux Systems. Based on industry usage and estimates, most of the public mail servers are currently running on Postfix.Installing the Software on LinuxSince, Postfix is a default package in the Ubuntu repositories, we can install it easily by using the ‘apt-get’ command. Before we install the packages, we need to update the system. We can do this by using the below command.Here is a sample demo, I used hanuman.com ... Read More
Given with the input as fraction i.e. a/b and c/d where a, b, c and d can be any integer values other than 0 and the task is to add these two fraction to generate their final sum.Fractions are represented by −a / b, where a is known as numerator and b is known as denominator.a and b can have any numeric values but b can have any numeric value other than 0.Sum of two fractions is represented as a / b + c / d, and the rule for adding the two terms is that their denominator must be ... Read More
In this article, we will learn how to change the host name on CentOS 7.x / RHEL 7.0, by default after installation on CentOS 7 or RHEL the default hostname will be localhost.localdomain. This hostname will be used for various services, unlike the older versions we will try to change the host name by changing /etc/sysconfig/networks or using the host name command to change the hostname and after multiple reboot of server the hostname remains as localhost.localdomain. The procedure for changing the host name in CentOS 7 or RHEL is totally different from the previous versions. we have 3 tools ... Read More
Secure Shell or SSH is a cryptographic (encrypted) network protocol operating at layer 7 of the OSI Model to allow remote login and other network services to operate securely over an unsecured network.OpenSSH is a premier connectivity tool for remote login with the SSH protocol. It encrypts all traffic to eliminate eavesdropping, connection hijacking, and other attacks. In addition, OpenSSH provides a large suite of secure tunneling capabilities, several authentication methods, and sophisticated configuration options. This article explains about important tasks to secure your SSH server setup.Use a Strong PasswordA password is a string of characters that people can use ... Read More
lsblk command is used to display a list of information about all available block devices. However, it does not give a list of information about RAM disks. Examples of block devices are hard disk, flash drives, CD-ROM. This article explains about how to find a list of block devices in Linux Machine.To install lsblk for Fedora and CentOS ,use the following command –$ sudo yum install util-linux-ngTo install lsblk for Ubuntu and Linux Mint ,use the following command –$ sudo apt-get install util-linux -yTo find the default list of all blocks, use the following command –$ lsblkThe sample output should be like ... Read More
Given with ‘a’(first term), ‘d’(common difference) and ‘n’ (number of values in a string) and the task is to generate the series and thereby calculating their sum.What is an Arithmetic seriesArithmetic series is the sequence of numbers with common difference where the first term of a series is fixed which is ‘a’ and the common difference between them is ‘d’.It is represented as −a, a + d, a + 2d, a + 3d, . . .ExampleInput-: a = 1.5, d = 0.5, n=10 Output-: sum of series A.P is : 37.5 Input : a = 2.5, d = 1.5, n ... Read More
Given with the rate of filling the tank, height of a tank and radius of a tank and the task is to check whether the tank is overflow, underflow and filled in given time.ExampleInput-: radius = 2, height = 5, rate = 10 Output-: tank overflow Input-: radius = 5, height = 10, rate = 10 Output-: tank undeflowApproach used below is as follows −Input the rate of filling time, height and radius of a tankCalculate the volume of a tank to find the original rate of flow of water.Check for the conditions to determine the resultIf expected < original ... Read More
nslookup is a network administration command-line tool available for many computer operating systems for querying Domain Name System (DNS) to obtain domain name or IP address mapping or for any other specific DNS record. This article explains about nslookup command in detail. Nslookup can be run in two modes, Interactive and Non-Interactive. The Interactive mode is used to query DNS-Server about various domains and hosts. Non-Interactive mode is used to query about information of a domain or host.To find out Find out “A” record (IP address) of Domain, use the following command –$ sudo nslookup tutorialspoint.comThe sample output should be ... Read More