rhel

How to add route on AlmaLinux

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By default, when a Linux system tries to communicate with a network address, the computer will send the request to the default gateway. The default gateway is usually a router, which can take the system’s request and forward it to the next hop, wherever that may be.

This behavior can be overridden by adding one or more static routes to the Linux machine. Such a configuration can be desirable if the network has multiple networks and routers, and a user needs to instruct the computer which way to route certain traffic.

Red Hat based distributions, such as almalinux, can use the nmcli command line utility to configure static routes, along with the ip route command and manual configuration of ifcfg files. Alternatively, you can use your installed desktop environment to apply the configuration. In this guide, we’ll go over the step by step instructions to add static routes on AlmaLinux through both command line and GUI methods. These instructions are applicable whether you’ve freshly installed AlmaLinux or have migrated from CentOS to AlmaLinux.

In this tutorial you will learn:

  • How to add a route via nmcli command
  • How to add a route via ip route command
  • How to add a route via ifcfg files
  • How to add a route via GNOME GUI
Adding a new static route in AlmaLinux

Adding a new static route in AlmaLinux

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Install ssh server on CentOS 8 / RHEL 8

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The SSH server might already be installed on your RHEL 8 / CentOS 8 system. If you need to install ssh, you can check the status of your SSH server using the systemctl status sshd command. We will then install the openssh-server package below by using the dnf command.

In this tutorial you will learn:

  • How to install SSH server onRHEL 8 / CentOS 8.
  • How to open SSH firewall port 22 on RHEL 8 / CentOS 8.
  • How to enable SSH to start after reboot on RHEL 8 / CentOS 8.

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How to increase swap size on RHEL 8 / CentOS 8

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On a system with memory-intense workload with common peak loads, a large swap memory can be useful to store large memory contents not needed at the moment. While using swap instead of memory will certainly have great impact on performance, sometimes this is preferable over adding more memory to the machine, as disk space is much cheaper. Sometimes there is simply no more memory, maybe a physical machine that is out of free slots, and there isn’t any larger memory modules on the market. At other times the slower performance on peak loads may be preferable over the application crashing with out of memory error.

In some cases swap memory needs to be increased, a live example could be expanding the memory in the machine, and so also expanding the swap space to match the double of the new memory size.

In this tutorial you will learn:

  • How to check swap space.
  • How to identify swap volume.
  • How to extend swap volume.
  • How to add another swap volume.

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Working with package dependencies on Red Hat Linux

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Objective

Our goal is to get used to the tools available to find out information about package dependencies on an RPM based system.

Operating System and Software Versions

  • Operating system: Red Hat Enterprise Linux 7.5
  • Software: rpm 4.11, yum 3.4.3

Requirements

Privileged access to the system.

Difficulty

EASY

Conventions

  • # – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
  • $ – given linux commands to be executed as a regular non-privileged user

Introduction

RPM, which stands for red hat package manager, is a well-known and mature package manager used by all Red Hat flavor distributions, as well as SuSE. With RPM the packager can define relations between packages, and even with versions of packages – for example, an Apache Tomcat server needs proper Java environment present to be able to run.

On the other hand, to install a Java environment, you don’t need a Tomcat server – you may decide to run some different Java based application, maybe one written by yourself started by hand when needed to do it’s job. In other words, the Tomcat server depends on Java.

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How to install gdb in RHEL 8

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Gdb or GNU Project Debugger is a great tool when you need to debug a program. You can set breakpoints, watch for value change of a variable, or even change a value for the program while it is halted at a point of it’s state, then continue, just to pick some of the features of gdb.

In this tutorial we will install gdb on RHEL 8, and test how it is working with a simple C application.

In this tutorial you will learn:

  • How to install gdb
  • How to compile a simple C application with debug symbols
  • How to set breakpoints in the running application with gdb
  • How to print actual values of given variables within the application

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How to install ActiveMQ on RHEL 8

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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

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Creating a Redhat package repository

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If your Red Hat server is not connected to the official RHN repositories, you will need to configure your own private repository which you can later use to install packages. The procedure of creating a Red Hat Linux repository is quite a simple task. In this article, we will show you how to create a local file Red Hat repository as well as a remote HTTP repository.

In this tutorial you will learn:

  • How to use official Red Hat DVD as repository
  • How to create a local file Red Hat repository
  • How to create a remote HTTP Red Hat repository

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How to install packages on RHEL 8 / CentOS 8 Linux System

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All modern linux distributions organize software in packages which contain applications binaries, files, metadata and information about the package dependencies, possible conflicts with other packages etc. The core Rhel package manager is called rpm itself, and it is the tool used also by dnf, the higher level package manager, which is capable to manage dependencies. A relatively recent technology , flatpak, let us install also sandboxed applications together with their runtimes.

In this tutorial you will learn:

  • The three main ways to install a package using rpm
  • How to install packages using dnf
  • How to install applications graphically from the gnome-software utility
  • How to install sandboxed applications with flatpak

rpm-manpage

The rpm package manager manual

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How to install apache tomcat on Linux RHEL 8 / CentOS 8

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In this tutorial we will learn how to install Apache Tomcat 8 application container to RHEL 8 / CentOS 8. We will be using the zip package available to download from the Apache Tomcat website. As this package will not handle setting up the environment, we will create it from the command line.

In this tutorial you will learn:

  • How to install Apache Tomcat from zip file
  • How to create the environment for the Tomcat server from command line
  • How to add basic service file to systemd
  • How to enable autostart, start and stop the Tomcat server
  • How to verify Tomcat is reachable

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How to enable SSH on Almalinux

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SSH is the primary method of remote access and administration on Linux systems. SSH is a client-server service providing secure, encrypted connections over a network connection. After installing AlmaLinux or migrating from CentOS to AlmaLinux, it will probably be one of the first things you want to configure.

In this guide, we’ll go over the step by step instructions to install and configure SSH on AlmaLinux. This will help you whether you just want to connect to remote systems via SSH or you want your own system to accept incoming connections as well.

In this tutorial you will learn:

  • How to install SSH
  • How to start and stop the SSH service
  • How to allow SSH through system firewall
SSH server enabled and running on AlmaLinux

SSH server enabled and running on AlmaLinux

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Unifying custom scripts system-wide with rpm on Red Hat/CentOS

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Objective

Our goal is to build rpm packages with custom content, unifying scripts across any number of systems, including versioning, deployment and undeployment.

Operating System and Software Versions

  • Operating system: Red Hat Enterprise Linux 7.5
  • Software: rpm-build 4.11.3+

Requirements

Privileged access to the system for install, normal access for build.

Difficulty

MEDIUM

Conventions

  • # – requires given linux commands to be executed with root privileges either directly as a root user or by use of sudo command
  • $ – given linux commands to be executed as a regular non-privileged user

Introduction

One of the core feature of any Linux system is that they are built for automation. If a task may need to be executed more than one time – even with some part of it changing on next run – a sysadmin is provided with countless tools to automate it, from simple shell scripts run by hand on demand (thus eliminating typo errors, or only save some keyboard hits) to complex scripted systems where tasks run from cron at a specified time, interacting with each other, working with the result of another script, maybe controlled by a central management system etc.

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