There are a few different ways that you can install an RPM package on RHEL 8 / CentOS 8 as oppose to package installation from a systems repository. They each have their own merits, but DNF should probably be your first choice in most situations. It's also good to remember that, for stability's sake, it's a good idea to limit your external RPM installs as much as possible.
Java is incredibly popular on servers, and if you plan on using RHEL 8 / CentOS 8, you'll need to install it. There are a couple of ways to install Java on RHEL, both from the open source OpenJDK packages and directly from Oracle.
In this part of RHCSA exam preparation you will learn how to manually change into a different boot targets. This article will also teach you how to set a default boot targets to automatically boot into graphical or multi-user target on Red Hat Enterprise Linux system.
In this part of RHCSA exam preparation we will turn our attention to links. There are two types of link, hard links and soft links. In this article we will talk about how to create and remove links and will also discuss some basic background behind both, the hard links and the soft links.
UNDER CONSTRUCTION RHCSA is a must have certification for anyone serious about getting a Linux system administration job. This RHCSA Exam Preparation Guide is currently under construction but is regularly updated with new topics. Please check back later.
If you are a beginner or somewhat new to GNU/Linux do not waste time by waiting but get started with a GNU/Linux command line basics before you do anything else. Understanding the GNU/Linux command line is an absolute must and will take you a long way on your RHCSA exam.
Understand and use essential tools
Access a shell prompt and issue commands with correct syntax
The hostname of your CentOS 7 Linux is defined by the file /etc/hostname thus setting a new hostname for your system is just a matter of editing this file and replace a current hostname definition line with new one. However, doing so will not update your system;s hostname immediately thus a preferred way of changing a hostname on CentOS 7 Linux is to use nmtui and more specifically its child nmtui-hostname. Using nmtui-hostname tool will make the process of changing your hostname rather simple as executing a single command. The following linux command will change the hostname to linuxconfig.org:
# nmtui-hostname linuxconfig.org
Hit the "OK" button on the pop-up dialog and you are done.
The sudo command allows regular users to execute commands with administrative/root privileges. By adding any user to predefined sudo group wheel will grant root privileges to execute any command as root user. Any attempt to use the sudo command for the non-sudo user will result in:
user is not in the sudoers file. This incident will be reported.
In this tutorial you will learn:
How to create sudo user on RHEL 8 / CentOS 8 system.
This article explains how to open FTP port 21 on RHEL 8 / CentOS 8 Linux system with the firewalldfirewall. The FTP protocol is primarily used by file transfer services such as, but not limited to, vsftpd FTP server. For more information visit our introduction guide to firewalld syntax and usage guide.
This article explains how to open HTTP port 80 and HTTPS port 443 on RHEL 8 / CentOS 8 system with the firewalldfirewall. HTTP and HTTPS protocols are primarily used by web services such as, but not limited to, Apache or Nginx web serves.
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
Firewalld is a powerful and yet simple to use tool to manage a firewall on RHEL 8 / CentOS 8 Server or GNOME workstation. Firewalld allows to manage open or close ports using predefined services as well as open and close user custom ports.
In this tutorial you will learn:
How to open and close ports on RHEL 8 / CentOS 8 with Firewalld.
How to open and close services on RHEL 8 / CentOS 8.
The firewall on RHEL 8 / CentOS 8 Linux system is enabled by default allowing for only few services to receive incoming traffic. FirewallD is the default daemon responsible for firewall security feature onRHEL 8 / CentOS 8 Server.
NOTE The nftables framework replaces iptables as a default network packet filtering feature on RHEL 8.
The following is a list of default firewall opened ports and configured settings on RHEL 8 / CentOS 8 Linux system using the firewalld dynamic firewall daemon:
# firewall-cmd --list-all
public (active)
target: default
icmp-block-inversion: no
interfaces: enp0s3
sources:
services: cockpit dhcpv6-client ssh
ports:
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:
In this tutorial you will learn:
How to check the firewall status onRHEL 8 / CentOS 8.
How to stop firewall on RHEL 8 / CentOS 8.
How to start firewall on RHEL 8 / CentOS 8.
How to permanently disable firewall on RHEL 8 / CentOS 8.
This artcile offers instructions on how to change or set timezone on RHEL 8 / CentOS 8 server or GNOME workstation using the command line tool timedatectl.
