YUM on RHEL 8

How to Install YUM on RHEL 8 / CentOS 8

Fedora made the change to DNF back with Fedora 22, but CentOS and RHEL have stayed with YUM, until now. RHEL has jumped to the next gen package manager, and that’s a good thing, but if you’re missing YUM or have scripts that rely on it, you’ll still have access to the old package manager. What’s even better, you don’t need to do anything extra.

In this tutorial you will learn:

  • How to Use YUM on RHEL 8 / CentOS 8
  • What is YUM on RHEL 8 / CentOS 8, Really
  • Is there a Difference?

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Use the repoquery command to list all available packages in RHEL 8 / CentOS 8

How to list installed packages on RHEL 8 / CentOS 8 Linux

There might come a time when you want to know if you have already installed a certain package on your RHEL 8 / CentOS 8. An application to be manually installed might require certain dependencies to work so you’ll have to check beforehand if these are satisfied. Or you might want to compile something and want to make sure you have all the right header libraries on your system.

In this tutorial you will learn:

  • How to use yum and dnf in RHEL 8 / CentOS 8 to list all packages
  • How to use the repoquery command to accomplish the same task
  • How to use the rpm command to list all packages installed on RHEL 8 / CentOS 8
  • How to filter the output of each command to seek certain packages
Use the repoquery command to list all available packages in RHEL 8 / CentOS 8

Use the repoquery command to list all available packages in RHEL 8 / CentOS 8

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Checking version of installed AWS CLI tools on RHEL 8

Install aws cli on RHEL 8 / CentOS 8

The AWS Command Line Interface (CLI) is a all-in-one tool to manage services available on AWS cloud. On RHEL 8 / CentOS 8 the AWS CLI can be installed by using the python package management system PIP.

In this tutorial you will learn:

  • How to install AWS CLI tools on RHEL 8 / CentOS 8
  • How to configure AWS CLI tools on RHEL 8 / CentOS 8
  • How to remove AWS CLI tools on RHEL 8 / CentOS 8

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Check open ports on RHEL 8 Linux firewall using firewall-cmd command.

How to check open ports on RHEL 8 / CentOS 8 Linux

Firewalld is a an underlining mechanism for firewall configuration on RHEL 8 / CentOS 8. Current RHEL 8 / CentOS 8 version of the Firewalld daemon is based on Nftables. To check open ports on RHEL 8 / CentOS 8 you can use the firewall-cmd command as shown below. We will also discuss how to check open ports remotely with the nmap command.

In this tutorial you will learn:

  • How to check open ports on RHEL 8.
  • How to check services on RHEL 8.
  • How to check open ports remotely using nmap.
  • How to list open ports and service with firewall-cmd.

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Install an RPM on RHEL 8

How to Install an RPM package on RHEL 8 / CentOS 8 Linux

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.

In this tutorial you will learn:

  • How to Install an RPM with DNF
  • How to Install an RPM with Yum
  • How to Install an RPM with RPM

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How to create a simple encrypted Two-Way SSH tunnel

How to create a simple encrypted Two-Way SSH tunnel

Why would you need to create a simple Two-Way SSH tunnel? In your Linux system administration job have you ever found your self in a situation in which you cannot SSH to a any of your servers/hosts that may be behind a firewall, NAT or otherwise obstructed from an easy access.

In order to gain the access, you would need to reconfigure the firewall or create VPN which could be an enormous overhead just because you need to execute few commands from now and then. With Two-Way SSH tunnel you can connect to any destination under a single condition, which is, the ability to ssh login from the destination to the source.

If you can do that, you can as well reverse login from source to destination even if it is behind firewall or NAT.

In this tutorial you will learn:

  • How to create Two-Way SSH tunnel

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User is not in the sudoers file error message on RHEL 8 / CentOS 8 Linux

RHEL 8 / CentOS 8 add user to sudoers

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.
  • How to add existing user to sudoers.

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RHEL 8 - HTTP & HTTPS protocol services. Open ports 80 & 443

RHEL 8 / CentOS 8 open HTTP port 80 and HTTPS port 443 with firewalld

This article explains how to open HTTP port 80 and HTTPS port 443 on RHEL 8 / CentOS 8 system with the firewalld firewall. HTTP and HTTPS protocols are primarily used by web services such as, but not limited to, Apache or Nginx web serves.

For more information about the firewalld firewall visit our introduction guide to firewalld syntax and usage guide.

In this tutorial you will learn:

  • How to open HTTP port 80 and HTTPS port 443.
  • How to open HTTP port 80 and HTTPS port 443 permanently.
  • How to list currently open ports/services.
  • How to close/remove HTTP port 80 and HTTPS port 443.

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Changing the IP address in RHEL 8 from within GNOME is a matter of a few clicks

How to change IP address on RHEL 8 / CentOS 8 Linux

Most IPs these days are automatically assigned through DHCP by either your ISP or your home router. But there may come a time when you wish to opt for a static IP address and you will want to change it. It may be that you are configuring a home LAN and you don’t want to use DHCP or simply want a static IP address that you can access from outside your home. In this tutorial we will learn how we can change the IP address in RHEL 8 / CentOS 8 Linus system.

In this tutorial you will learn:

  • How to change the IP address in RHEL 8 / CentOS 8 using GNOME
  • How to change the IP address by editing configuration files
  • How to manually change your DNS server
  • How to restart networking in RHEL 8 / CentOS 8

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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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