Check hostname on RHEL 8 Linux system using hostnamectl command

RHEL 8 / CentOS 8 change hostname

A hostname is the label or name linked to a device on a network. Its main purpose is to recognize a device on a specific network or over the internet. There are three different hostname types:

  • Static – Most of the time you will be interested in this type of hostname which is defined by user and the /etc/hostname configuration file.
  • Transient – This type of hostname is defined within kernel space and by default it is set to be the same as the static hostname. Transient hostnames can be set/updated by DHCP or mDNS at runtime.
  • Pretty – Pretty hostname allows for additional characters as per UTF8 character set hence serving rather only for presentation purposes. The pretty hostname also allows to include spaces.

This article will explain how to change or set hostname on RHEL 8 / CentOS 8 Linux server or workstation. To change hostname you will use the hostnamectl command.

In this tutorial you will learn:

  • How to change the static hostname.
  • How to change the transient hostname.
  • How to change the pretty hostname.
  • How to check the current hostname.

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Stopping firewall on Red Hat Enterprise Linux 8.

How to stop/start firewall 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.
  • How to enable firewall to start after reboot.

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JSch example execution

Executing commands on a remote machine from Java with JSch

SSH is an every-day tool of any Linux System Administration job. It is an easy and secure way to access remote machines on the network, transfer data and execute remote commands. Apart from interactive mode, there are many tools exist that enable automation of remote tasks that also rely on the existing ssh server/client architecture. For one such tool, you can read about ansible on Ubuntu for example. You can also find many implementations of the ssh client, but what about accessing the abilities ssh provides from code?

JSch is a project that implements the ssh protocol in Java. With it’s help, you can build applications that are capable to connect to and interact with a remote or local SSH Server. This way your application is capable of managing any aspect of the target machine that you could complete with your native ssh client, which gives yet another powerful addition to the already vast Java toolset.

In this article we will import JSch into our Java project, and develop the minimal necessary code pieces to create an application that can log in to a remote machine’s ssh server, execute some commands in the remote interactive shell, closes the session, then presents the output. This application will be minimal, however, it may give a hint of the power it provides.

In this tutorial you will learn:

  • How to import JSch into your Java project
  • How to setup the test environment
  • How to implement the UserInfo interface in a custom class
  • How to write an application that initiates interactive ssh session

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Debian package

Easy way to create a Debian package and local package repository

This article describes a simple way to create a home made debian package and include it into a local package repository. Although we could use an existing Debian/Ubuntu package, we will start from scratch by creating and packaging our own trivial application. Once our package is ready, we will include it into our local package repository. This article illustrates a very simplistic approach, however it may serve as a template in many different scenarios.

In this tutorial you will learn:

  • How to create a trivial debian package
  • How to create a local debian repository
  • How to add the repository to the list of software sources

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WPA Supplicant Configuration on Debian 10

How to Connect To WiFi From the CLI on Debian 10 Buster

Not all Debian systems have a GUI, and even though using WiFi on a server isn’t common, there are plenty of instances where you’re using WiFi with a headless setup, like on a Raspberry Pi. It’s not difficult to connect using only the tools provided out of the box in Debian.

In this tutorial you will learn:

  • How to Scan for a Network
  • How to Generate a WPA_Supplicant Config
  • How to Set up a WPA_Supplicant Config File
  • How to Connect to Your WiFi

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Check Linux Mint version from command line

Check Linux Mint Version

There are number of ways on how to check Linux Mint version. Since Linux Mint comes with number of available Desktops the graphical user interface may differ from user to user hence the procedure is also different. From this reason the easiest and perhaps even recommend solution is to simply open up a command line terminal and execute the following command cat /etc/issue.

To check a version of other Linux distributions visit our how to check Linux version guide.

In this tutorial you will learn:

  • How to check Linux Mint version from graphical user interface
  • How to check Linux Mint version from the command line

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How to check Linux version

How to check Linux Version

The common scenario is that you have been given an access to a Linux system physically or via remote login and you have no idea what Linux version is installed on this particular system. Given that many of the today’s Linux Distributions have implemented systemd as part of their core design, to check for a Linux version is in many cases relatively simple procedure.

The simplest way to check Linux version is by using the hostnamectl command without any arguments. For example the below hostnamectl command will return the Linux distribution name, version and codename in use along with the currently loaded Linux kernel version:

$ hostnamectl 
   Static hostname: x220
         Icon name: computer-laptop
           Chassis: laptop
        Machine ID: 2d4efda5efb0430faeb2087d0a335c6b
           Boot ID: f8c4a3a776a74d42878347efc2c00634
  Operating System: Debian GNU/Linux 10 (buster)
            Kernel: Linux 4.9.0-9-amd64
      Architecture: x86-64
DID YOU KNOW?

It is a common mistake to refer to the entire GNU/Linux operating system simply as Linux. The important note here is that the so called Linux is actually only the Kernel part of the system whereas GNU is the actual system as in collection of pre-compiled binaries, libraries and system tools. Both GNU and Linux kernel must function in tandem in order for the operating system to actually work.

Hence, one cannot exists without the other, so next time when you talk about your operating system and you wish to be technically correct, refer to it as GNU/Linux or simply as Lignux.

In this tutorial you will learn:

  • Basic introduction to Linux package
  • How to check system architecture and Linux kernel version
  • How to check CPU architecture
  • How to check CentOS, Redhat, Debian, Ubuntu, Mint, Arch, Fedora Linux system version

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Linux FileSystem Hierarchy Standard

Linux Filesystem Navigation Basics

This article explains basic commands for navigation within Linux file system. The diagram below represents (part of) a Linux file system know as Filesystem Hierarchy Standard. A line from one node to a node on its right indicates containment. For example, the student directory is contained within the home directory.

In this tutorial you will learn:

  • How to use pwd command
  • How to use cd command
  • How to navigate to user home directory
  • Difference between relative vs absolute
  • What is a parent directory

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Retrieving Google Chrome browser version

How to check Google Chrome browser version

In this article we will discuss few possible ways on how to check your Google Chrome browser version. Expect from the last check Google Chrome browser solution, where the actual Linux command line terminal is used to determine the chrome version, the guide should provided you with operating system agnostic solution. That being said, at least one of the below steps should help you out regardless of your operating system or device ( mobile, table, PC ).

In this tutorial you will learn:

  • How to check Chrome browser version using help page
  • How to check Chrome browser version using external landing page
  • How to check Chrome browser version using chrome version page
  • How to check Chrome browser version from the command line

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Command-line programs for everyday use in Linux

Introduction

I must admit, I’m a command line geek. Whenever I have the chance, regardless of desktop environment or distribution, I open a terminal and start fiddling something. This does not mean everyone must be like me, of course. If you’re the person who is mouse and GUI-oriented, no problems. However, there are situations when all you have at your disposal for a while is the command line. One of those situations might be an upgrade of your kernel/graphics drivers that leave you high and dry until the bug is reported and the developers look at the issue. You have to send a very important e-mail or you have to check the evolution of prices of your favorite laptop. All the essential desktop tasks (with some exceptions, though) that you do on a GUI-enabled machine can be done on a CLI-only machine as well, so if you’re interested…

The tasks

The everyday tasks we will refer to are the ones we usually do in a usual day, be it a work day or a weekend. We need to check our mail, maybe watch something on Youtube (yes, it’s possible), chat with our friends or simply browse away from URL to URL. These are the kinds of things we are talking about in this article. By the way, another huge advantage of the CLI approach is (besides efficiency and low resources) uniformity. You don’t have to worry, if you use many Linux computers, that some of them won’t have your favorite desktop installed: these programs we will tell you about work everywhere, GUI available or not, as long as you have a terminal emulator installed, of course. Note that this article is comprised only of ideas and suggestions, and will not guide you step-by-step on how to use the presented applications.

Web browsing

It’s true, you can’t see images , but they are practical to have, way faster and even more secure, because some of them don’t even support Javascript unless you tweak their compile options. Ladies and gents, I give you links, elinks and lynx. You can install them on almost any distribution with the native package manager, or you can install them from source, and of course compilation will not take a lot, because there are no heavy dependencies. links also offers a command-line flag (-g from graphical) that, if compiled with the right options, will offer you a very simple but fast GUI browser.

On Debian, when I wanted to do ‘links -g’, I got “Graphics not enabled when compiling (use links2 instead for graphics mode)”. After installing it, typing

  $ links2 -g

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