Software RAID Recovery Tutorial

This tutorial will walk through the troubleshooting and recovery of a failed disk on a Software RAID setup. Especially mirroring the boot partition which is important when replacing disk and making sure the OS boots up properly after replacement.  This tutorial was done on Ubuntu 14.04 but should still work on other distributions such as RHEL and CentOS.

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Redirect HTTP to HTTPS on Apache

SSL secured websites or HTTPS has now become a must to have on website, especially those handling sensitive client information. Having a HTTPS enabled website means that a intruder can’t intrude to communication between users and website. HTTPS not only secures communication but is now a requirement for many new features like http2, which requires you to have https enabled on your server. Having a HTTPS enabled website also improves your Google SEO (Search Engine Optimization) ranking.

In this tutorial, we will discuss two methods on how we can redirect http traffic to https on Apache web servers.
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Setup Master Slave replication in MariaDB

Databases are arguably one of the main component of any modern application. And one of the most popular implementation of SQL databases is Mysql or the new replacement MariaDB. As a system administrator, you probably have installed and configured a database before. This tutorial will walk though setting up the master-slave replication of MariaDB.
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How to remove unused kernel images from CentOS/RHEL systems

Every time you update your CentOS Linux and the update includes a new kernel image update the system will not remove your old kernel but it will cumulatively add new kernel to the top of your Linux kernel installed list. Normally, this does not present any issue to your running system and you are not required to take any action to remove any old and unused kernel images.

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Recover disk usage after deleting large file in Linux

Disks getting full on Linux is a common scenario any administrator have probably experienced. There are usually some large files in /var/log directory that can be compressed or deleted to save disk space. Have you ever experienced deleting a large log file and noticed that the disk usage remained the same ? It’s as if the file size usage is not released even though you’ve deleted it?

This scenario can happen if you deleted/renamed/moved an existing file that is currently in use by a running program. This usually happens on log files that are not rotated regularly and then when the file size becomes large, you deleted (or compressed) the file without even checking if it is in-use. Don’t worry, you can still recover your disk space as shown from the example below.

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Configuring Elastic Load Balancer on Amazon EC2

Load balancers are used to distribute the requests/queries to multiple server instances. Most web infrastructures have multiple front-end servers that share the load of the application. Although there are multiple server instances, the end-user only see them a single node. In this tutorial, I’ll walk you on how to configure an Elastic Load Balancer on Amazon, add your web server nodes and point your domain name to the EC2 load balancer.

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Cloning you Instances on Amazon EC2

Multiple front-end web server setups are almost always in use these days. Instead of just one server serving web traffic, you create two or more servers which will share the load evenly to serve requests from users. These servers usually connect to a backend database server. On this tutorial, we’ll walk through the steps on adding another web-front end server by cloning you current web server node.

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