Apache Hadoop is an open source framework used for distributed storage as well as distributed processing of big data on clusters of computers which runs on commodity hardwares. Hadoop stores data in Hadoop Distributed File System (HDFS) and the processing of these data is done using MapReduce. YARN provides API for requesting and allocating resource in the Hadoop cluster.

The Apache Hadoop framework is composed of the following modules:
  • Hadoop Common
  • Hadoop Distributed File System (HDFS)
  • YARN
  • MapReduce

This article explains how to install Hadoop Version 2 on RHEL 8 or CentOS 8. We will install HDFS (Namenode and Datanode), YARN, MapReduce on the single node cluster in Pseudo Distributed Mode which is distributed simulation on a single machine. Each Hadoop daemon such as hdfs, yarn, mapreduce etc. will run as a separate/individual java process.

In this tutorial you will learn:
  • How to add users for Hadoop Environment
  • How to install and configure the Oracle JDK
  • How to configure passwordless SSH
  • How to install Hadoop and configure necessary related xml files
  • How to start the Hadoop Cluster
  • How to access NameNode and ResourceManager Web UI

Redmine is a popular open source project management web application. It supports mayor databases like MySQL and PostgreSQL as backend, and you can also change the frontend to Apache from the WEBrick (recommended for production use) webserver shipped with the installation. In this article we will install the latest Redmine on RHEL 8 / CentOS 8, using PostgreSQL as backend, but we will leave the default WEBrick as frontend, which will serve our tests perfectly.

Do not expect this process to be an easy one, nor error-free. Even following these steps to the letter, some errors will surely happen, the setup seem to handle sudo steps somewhat inconsistently - but the solutions are also included which will guide trough these errors.

In this tutorial you will learn:
  • How to install required operating system packages
  • How to setup the database
  • How to install the Redmine application
  • How to start and login to the application

Xinetd, or the Extended Internet Services Daemon, is a so-called super-server. You can configure it to listen in the place of many services, and start the service that should handle an incoming request only when there it actually arrives to the system - thus saving resources. While this may not seem to be a big deal on a system where traffic is relatively permanent, this service in the front of another approach does have some neat advantages, like logging or access control.

In this article we will install xinetd on a RHEL 8 / CentOS 8, and we'll put the sshd daemon under it's care. After verifying the setup, we'll tweak the configuration a bit to see the access control in action.

In this tutorial you will learn:
  • How to install xinetd
  • How to setup sshd on RHEL 8 / CentOS 8 as an xinetd service
  • How to allow access only from a specific network to the sshd service from xinetd
  • How to audit traffic from xinetd log entries

When speaking of virtualization, VMware is a solution that can't be ignored. While the true power of virtualization lives in the datacenters, we live in the age where anyone can run a virtual machine or two on a desktop or a laptop, given it is equipped with enough resources. These virtual machines are computers running inside a computer, and this setup has countless benefits and use cases. For instance, if you have a new software you'd like to test, you can do so in a virtual machine before installing it directly on a device you use for everyday work.

To work with these virtual machines with ease, we can integrate them with our Hypervisor - in this case, VMware - to enable the operating system running as guest to use the capabilities of the virtualization software. In this tutorial we will install the integration software, called VMware Tools on a virtual machine running RHEL 8 / CentOS 8, that is hosted in VMware Player. The same in-guest steps apply on the datacenter version of VMware regarding the tools installation. Note however, that Red Hat ships the open-vm-tools with the distribution, which is what VMware also recommends to use instead of the tools we'll now install. Why are the tools shipped with the distribution recommended? They can be updated along with the distribution within the regular update process, while VMware's tools need to be updated by hand (or automation, but unneeded effort anyway).

While the following steps will result in a working integration, please consider the above when you setting up your virtual systems. Outdated virtualization integration tools are a bad thing, which you will experience when you upgrade your hosts, and hundreds of alerts will appear on the vCenter consoles.

In this tutorial you will learn:
  • How to download VMware tools using VMware Player
  • How to present installation source to the virtual machine
  • How to remove open-vm-tools
  • How to install and configure VMware Tools

Disk and space management is an essential knowledge of a sysadmin. It is his or her everyday job to handle disk issues. As part of the RHCSA exam preparation, we will learn how to add new space of various types to the system, using the tools provided by RHEL8. We already covered many of these tasks, and in this tutorial we will focus on adding new space without harming the data contained in the system.

In this tutorial you will learn:
  • How to add new partitions to RHEL8
  • How to add new logical volumes to RHEL8
  • How to add swap to RHEL8

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