GNU/Linux filesystem permissions and rights are the basis of the system's security, and one of it's principles is the clear separation of rights to files and folders. In a heavily multiuser environment, such as a school's server, file rights prevent a user by default to accidentally delete or overwrite another's documents. However, there are use cases where multiple users need to access (read, write, and even delete) other user's files - such may be the case in the above mentioned school server, where students work on the same project. In this section of RHCSA exam preparation we will learn how to create an environment for such collaboration, using the setgid (set groupID) technique. Note that while we perform these steps on a recent operating system, the setgid isn't a new thing, and you will find it in any and all distributions.

In this tutorial you will learn:
  • How to add users to a supplementary group
  • How to use set-GID on a directory
  • How to check proper ownership within the set-GID directory
  • How to use the special directory as a member of the group

firewalld is a front-end for the built in netfilter firewall on Linux systems. The main advantage of firewalld over using raw nftables/iptables commands is that it's easier to use, especially for more complex firewall features like timed rules. In this regard, it's similar to the uncomplicated firewall (ufw) that comes installed by default on Ubuntu systems.

On CentOS, firewalld is the default firewall interface and should already be installed on your system. In this guide, we'll take you through the installation of firewalld on CentOS, which includes some basic usage commands so you can get started managing the firewall.

In this tutorial you will learn:
  • How to install and update firewalld
  • firewalld basic usage commands

Like all Linux distros, it's important to keep your CentOS system up to date in order to make sure that you have the latest security updates and newest features. Updating the system usually involves simply upgrading all installed packages to their latest versions. Every few years, there's a new version of CentOS released, which requires a more involved update process to install.

In this article, we'll cover updating a CentOS system on a per package basis and upgrading the entire operating system. This can be done via command line and GUI. Both methods will be shown in this guide, so you can pick whichever is easier for you.

The process for upgrading a CentOS system is a little different depending on which version you have installed. The latest version of Centos has moved to the dnf package manager. Previous to Centos 8, yum was the package manager used. Regardless of which version you're running, we'll show you the proper commands so you can update your system.

In this tutorial you will learn:
  • How to update CentOS packages via command line
  • How to update CentOS packages via GUI
  • How to upgrade entire CentOS system

Red Hat Enterprise Linux is a commercial Linux distribution built for powering the servers of corporations and data centers. It's a robust distro with the features and stability that businesses crave for high availability and predictability.

The big appeal of Red Hat, though, is its support system. That's the main thing you're paying for, after all. If something doesn't operate as expected, businesses want someone to turn to for support so they can face as little downtime as possible. Red Hat experts are only a phone call away for subscribers.

The support feature is what really sets Red Hat apart from other Linux distributions that could also perform the same job very well, such as CentOS, Fedora, and OpenSUSE. For other most popular Linux distributions please visit our dedicated linux download page.

Red Hat offers training and certification programs to prospective Linux system administrators. This is another big plus for businesses, as they can buy training for their employees or vet new recruits by their certifications. Such training and certifications are rare to find in the Linux world, being that Linux distros are mostly free and run by a community of volunteers.

If you are a system administrator looking to get into Red Hat, most or all of your experience with CentOS and Fedora Server should transfer over to Red Hat, since the three distributions are closely related.

CentOS is one of the leading Linux distributions available. It's developed by The CentOS Project, which is an affiliate of Red Hat. As CentOS is based on Red Hat Enterprise Linux, it's naturally more geared toward servers and workstations, though it can still work well as a desktop operating system for some people. For other most popular Linux distributions please visit our dedicated linux download page.

CentOS excels at being very stable and predictable, the exact qualities you'd hope to find in a server OS. It's very similar to RHEL in most respects except that it's completely free. If a user or organization needs a reliable distribution and can do without the commercial support that RHEL provides, CentOS is a perfect choice.

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

Kickstart installations let us easily script and replicate unattended or semi-unattended installations of Fedora, Red Hat Enterprise Linux or CentOS. The instructions needed to install the operating system are specified, with a dedicated syntax, inside a Kickstart file which is passed to the Anaconda installer. In this tutorial we will see how to reuse an already existing LUKS (Linux Unified Keys Setup) container when performing a Kickstart installation: this is something that cannot be achieved just with Kickstart instructions and requires some extra steps.

In this tutorial you will learn:
  • How to use an existing LUKS container when performing a Kickstart installation of Fedora, RHEL or CentOS
  • How to create and use an updates.img file to be used with the Anaconda installer.

Apache ActiveMQ is a widely used messaging server written in Java. As messaging services commonly do, it creates a bridge between heterogeneous systems for reliable data exchange in the form of messages pushed into queues by producer clients, where they wait to be "read", or consumed by consumer clients.

Naturally a system that is client to ActiveMQ can be both producer and consumer, and more than one systems can subscribe to a queue or topic, thus enabling flexible communication between these client systems. Many different platforms and protocols can be used to connect to ActiveMQ, increasing it's usefulness even more.

In this tutorial we will install Apache ActiveMQ on Red Hat Enterprise Linux 8 from tarball, add the systemd unit files for ease of use, and access the admin page of our new service to create a queue.

In this tutorial you will learn:
  • How to install ActiveMQ from tarball
  • How to set up environment from the command line
  • How to add systemd unit files for ActiveMQ
  • How to access the admin page

RHEL 8 is the latest release of the popular enterprise distribution. Whether you're installing RHEL for the first time, or you're installing the latest version, the process is going to be fairly new to you. This guide walks you through the steps in the latest Red Hat Anaconda installer.

In this tutorial you will learn:
  • How to Set Your Language
  • How to Set Your Localization
  • How to Select Your Software
  • How to Configure Your Storage
  • How to Configure Your Network
  • How to Set Your Security Policy

Apache Spark is a distributed computing system. It consists of a master and one or more slaves, where the master distributes the work among the slaves, thus giving the ability to use our many computers to work on one task. One could guess that this is indeed a powerful tool where tasks need large computations to complete, but can be split into smaller chunks of steps that can be pushed to the slaves to work on. Once our cluster is up and running, we can write programs to run on it in Python, Java, and Scala.

In this tutorial we will work on a single machine running Red Hat Enterprise Linux 8, and will install the Spark master and slave to the same machine, but keep in mind that the steps describing the slave setup can be applied to any number of computers, thus creating a real cluster that can process heavy workloads. We'll also add the necessary unit files for management, and run a simple example against the cluster shipped with the distributed package to ensure our system is operational.

In this tutorial you will learn:
  • How to install Spark master and slave
  • How to add systemd unit files
  • How to verify successful master-slave connection
  • How to run a simple example job on the cluster

OTRS is an open source service management solution used by many companies around the world. It's extensibility and ability to integrate with other systems no doubt add to it's popularity. Written in perl, this software will run on mostly anything, and it's low requirement on resources makes it ideal even for a small business to start ticketing, or standardize their internal processes.

In this tutorial we will install OTRS on a Red Hat Enterprise Linux 8. Keep in mind that the steps described below are only apply to version 6.0.14, Community Edition. For example, version 6.0.15 will not work when the below steps are performed on the same environment.

In this tutorial you will learn:
  • How to install OTRS from tarball
  • How to solve dependencies
  • How to configure the environment
  • How to run the web installer
  • How to login to the service

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