Author: Rahul

Latest Linux operating systems like CentOS/RedHat 7 and Fedora 21 has stopped using iptables and start now using dynamic firewall daemon firewalld which provides a dynamically managed firewall. It supports for network and zones to assign a level of trust to a network, connections, and interfaces. Firewalld also provides an interface for services or applications to add firewall rules directly. This article will help you to disable firewalld service and then install and use iptables on CentOS and Red Hat 7 Systems. Visit here to read more about firewalld. Disable Firewalld Service Before installing and using iptables services on CentOS…

One of the most important aspects of running a Linux server is ensuring that it is secure. This means protecting against unauthorized access and preventing potential attackers from exploiting vulnerabilities in your system. One way to enhance the security of your Linux server is to disable root SSH login and create a sudo user. In this article, we’ll provide a step-by-step guide for doing just that. Step 1: Create a Sudo User The first step in enhancing the security of your Linux server is to create a sudo user. This user will have elevated privileges and will be able to…

Apache is the most popular web server for Linux web servers. Most of the Linux system administrator’s start with Apache (httpd) web server from there learning phase, Even I also used Apache web server during learning. At the initial level the System administrator works with Apache. Most of them used default configuration but they don’t know how Apache works, how it handles incoming connection or multiple processes. Apache uses one of following MPM (Multi-Processing Module) for handling incoming requests and processes them. Both have their own working type. Below is some basic details about both MPM and there working. Prefork…

Today while deploying a war file (development site code) in Tomcat 8, I faced the following issue regarding upload limit size in Apache Tomcat server. So I decided to increase limit Tomcat upload file size limit to higher than the default. The default upload limit is set to 50 MB. Caused by: org.apache.tomcat.util.http.fileupload.FileUploadBase$SizeLimitExceededException the request was rejected because its size (128382112) exceeds the configured maximum (104828800) Increasing Upload Size Limit You can increase the Tomcat server upload file size limit by the editing webapps/manager/WEB-INF/web.xml configuration file and searching for the below content. sudo nano /path/to/tomcat/webapps/manager/WEB-INF/web.xml Update the following section: <multipart-config>…

In the world of database management, ensuring the safety and integrity of your data is paramount. PostgreSQL, with its robust set of tools, offers powerful methods for backing up and restoring databases. This comprehensive guide aims to equip database administrators and developers with the knowledge needed to effectively dump and restore PostgreSQL databases, ensuring that data is securely backed up and can be restored when needed. Introduction PostgreSQL, an advanced open-source relational database management system, offers various methods for data backup and recovery. Among these, the pg_dump and pg_restore commands are widely used for their versatility and effectiveness in managing…

If you’ve spent any significant amount of time working in a Linux environment, you’re likely familiar with the SCP (Secure Copy) command. This handy tool enables you to securely transfer files between different hosts over a network using the SSH (Secure Shell) protocol. However, there might be instances where you encounter the error message: ‘bash: scp: command not found’. This article aims to help you troubleshoot this error, getting you back to work as soon as possible. What Causes the Error? The error message ‘bash: scp: command not found’ typically appears when the SCP command isn’t installed or accessible on…

This guide is designed to assist you in finding out the size of databases and tables on your PostgreSQL server, making it easier to manage your data effectively. To start, you’ll need to access your server via the command line and establish a connection with the PostgreSQL server. Here’s how you can determine the sizes of your databases and tables in PostgreSQL using straightforward commands. 1. Determine PostgreSQL Database Size Using SQL Queries To find out how much space your PostgreSQL database occupies, follow these steps: First, open a terminal and log into the PostgreSQL command interface: sudo -u postgres…

PostgreSQL is a powerful open-source relational database management system, known for its robustness and extensibility. As a database administrator or developer, one of the fundamental tasks you’ll often need to perform is listing databases and tables within PostgreSQL. In this step-by-step tutorial, we will walk you through the process of listing databases and tables using various methods and PostgreSQL commands. Listing Databases in PostgreSQL Open your terminal or command prompt. To access the PostgreSQL command-line interface (psql), type the following command, replacing your_username with your actual PostgreSQL username: psql -U your_username You will be prompted to enter your password. Once…

Sendmail is a MTA (Mail Transfer Agent) server used for transferring email from between different hosts. Sendmail uses SMTP (Simple Mail Transfer Protocol) protocol. Most of the system administrators preferred to use Sendmail server as MTA than other MTAs. RHEL 5 or its earlier versions were using Sendmail as a default mail server, But newer version’s of RHEL based systems adapted postfix as a default mail server. Most of the users are familiar with Sendmail and want to use it with version 6 also. This article will help users for installing Sendmail server on RHEL 7/6/5 or with minimal configuration.…

In the ever-expanding world of big data, Elasticsearch has emerged as a front-runner in the search and analytics engine space. Its ability to handle large volumes of data efficiently makes it a go-to choice for many organizations. This article delves into the process of setting up a multi-node Elasticsearch cluster on an Ubuntu server, providing a detailed and comprehensive guide for systems administrators, DevOps engineers, and data professionals. This guide focuses on establishing a three-node Elasticsearch cluster on Ubuntu, specifically configured for the following nodes: NODE_1: 192.168.10.101 NODE_2: 192.168.10.102 NODE_3: 192.168.10.103 What is Elasticsearch? Elasticsearch is an open-source, distributed search…