How to set up EPEL repository on CentOS

If you are using CentOS or RHEL, it is strongly recommended that you configure EPEL (Extra Packages for Enterprise Linux) repository on your system. EPEL is a community effort to create a repository of high-quality add-on free software packages for RHEL-based distributions. Once you set up EPEL repository, you can use yum command to install […]
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How to turn your CentOS box into an OSPF router using Quagga

Quagga is an open source routing software suite that can be used to turn your Linux box into a fully-fledged router that supports major routing protocols like RIP, OSPF, BGP or ISIS router. It has full provisions for IPv4 and IPv6, and supports route/prefix filtering. Quagga can be a life saver in case your production […]
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How to harden Apache web server with mod_security and mod_evasive on CentOS

Web server security is a vast subject, and different people have different preferences and opinions as to what the best tools and techniques are to harden a particular web server. With Apache web server, a great majority of experts -if not all- agree that mod_security and mod_evasive are two very important modules that can protect […]
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How to manage LVM volumes on CentOS / RHEL 7 with System Storage Manager

Logical Volume Manager (LVM) is an extremely flexible disk management scheme, allowing you to create and resize logical disk volumes off of multiple physical hard drives with no downtime. However, its powerful features come with the price of somewhat steep learning curves, with more involved steps to set up LVM using multiple command line tools, […]
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How to secure a LAMP server on CentOS or RHEL

LAMP is a software stack composed of Linux (an operating system as a base layer), Apache (a web server that “sits on top” of the OS), MySQL (or MariaDB, as a relational database management system), and finally PHP (a server-side scripting language that is used to process and display information stored in the database). In […]
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How to install Puppet server and client on CentOS and RHEL

As a system administrator acquires more and more systems to manage, automation of mundane tasks gets quite important. Many administrators adopted the way of writing custom scripts, that are simulating complex orchestration software. Unfortunately, scripts get obsolete, people who developed them leave, and without an enormous level of maintenance, after some time these scripts will […]
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How to check RPM package dependencies on Fedora, CentOS or RHEL

A typical RPM package on Red Hat-based systems requires all its dependent packages be installed to function properly. For end users, the complexity of such RPM dependency is hidden by package managers (e.g., yum or DNF) during package install/upgrade/removal process. However, if you are a sysadmin or a RPM maintainer, you need to be well-versed […]
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How to analyze Squid logs with SARG log analyzer on CentOS

Squid provides many useful proxy features such as caching, access control, anti-virus, load balancing, authentication, rate-limiting, and so on. However, analyzing a raw Squid log file is not straightforward. For example, how could you analyze the time stamps and the number of hits in the following Squid log? 1404788984.429 1162 172.17.1.23 TCP_MISS/302 436 GET http://facebook.com/ […]
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