administration

Allowing access from a certain network segment to sshd.

How to install and setup an example service with xinetd on RHEL 8 / CentOS 8 Linux

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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

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HAProxy Architecture

Install and Configure HAProxy on RHEL 8 / CentOS 8 Linux

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HAProxy or High Availability Proxy is an open source TCP and HTTP load balancer and proxy server software. HAProxy has been written by Willy Tarreau in C, it supports SSL, compressions, keep-alive, custom log formats and header rewriting. HAProxy is a fast and lightweight proxy server and load balancer with a small memory footprint and low CPU usage. It is used by large sites like Github, StackOverflow, Reddit, Tumblr, Twitter and others. It has become the most popular software load balancer and proxy server in the past years.

In this tutorial, you will get through the HAProxy installation and configuration on RHEL 8 / CentOS 8. We will install HAProxy on a single server and then install Nginx web server on the other servers. HAProxy will act as a load balancer for the Nginx web servers.

In this tutorial you will learn:

  • HAProxy Architecture and Concepts
  • Configure hosts file for name resolution
  • Install and Configure HAProxy
  • Install and Configure Nginx
  • Testing the Load Balancing feature
  • Access the HAProxy Stats URL

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Retrieving Google Chrome browser version

How to check Google Chrome browser version

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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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Ansible Architecture

How to install and configure Ansible on Redhat Enterprise Linux 8

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This tutorial covers step by step installation and configuration of Ansible on Redhat Enterprise Linux 8.
Ansible is the leading Open Source configuration management system. It makes it easy for administrators and operations teams to control thousands of servers from central machine without installing agents on them.

In this tutorial you will learn:

  • Ansible Overview
  • Install and Configure Python
  • Set Password-less SSH
  • Install Ansible
  • Testing and Managing the Ansible

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Checking a website's SSL certificate with openssl.

How to install ssl on RHEL 8 / CentOS 8

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As interconnected computer networks enter more and more fields of everyday life, cybersecurity is getting louder and louder. We protect our websites, the traffic on our websites, the computers we initiate the traffic from, maybe (part of) the disks our operating system run from, our connection to work, the computers we attach to at work, and so on.

openssl is an essential tool on any recent GNU/Linux distribution if one have to work with various certificates.

In this tutorial we will install (and reinstall) the openssl package, and test it’s functionality by checking a website’s certificate chain with it’s help.

In this tutorial you will learn:

  • How to install openssl
  • How to reinstall openssl
  • How to check a website’s SSL certificate chain with openssl

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Examples page served by Apache Tomcat

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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VNC connection to RHEL8 with Remmina.

How to install vnc server on RHEL 8 / CentOS 8

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Remote connection to computers is as old as computer networks. Accessing the graphical interface (GUI) is a convenient way of working on a remote desktop. We can leave our graphical programs running and working, and we don’t need to keep the session open – we simply reconnect when we feel to do so.

VNC server is well-known graphical session server enabling remote connections that we can run with a non-privileged user. This way many users can access their own desktop on the same machine remotely, and will not block each other (apart from maybe using up the resources of the remove machine).

In this tutorial you will learn:

  • How to install required packages.
  • How to setup and start the VNC server on RHEL 8.
  • How to connect to a graphical session remotely.
  • How to run graphical programs in the xterm session.

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Status output of rsyslog service with systemctl.

How to install syslog on RHEL 8 / CentOS 8

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The syslog functionality is one of the main tools for a sysadmin. While writing logfiles with events of interest is a common feature of any application, having a system-wide logging functionality means all logs can be handled as one on the system. But syslog does not stop there. With these tool, a sysadmin can centralize log processing in the datacenter by forwarding the incoming events from applications to central logservers, where they can be processed at a large scale.

Centralized logging is an overkill on a home system with a few computers, but already have it’s benefits around a dozen machine. For example, a dozen desktops sending all their logfiles to a central logserver mean they don’t need to store them on the long run, the logs will occupy disk space in the logserver. The admin can check for problems in only one place (possibly by means of automated reports), the logs can be preserved in a safe way by the means of backups, stored more effective by means of heavy compressing, and will not be lost on a client’s failure or user error.

In this tutorial you will learn:

  • How to install rsyslog package on RHEL 8 / CentOS 8.
  • How to verify successful install.
  • How to start, stop and autostart rsyslog service.
  • How to test syslog functionality with logger.

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Ubuntu UFW

How to configure firewall in Ubuntu 18.04

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A properly configured firewall is one of the most important aspects of the overall system security. By default Ubuntu comes with a firewall configuration tool called UFW (Uncomplicated Firewall).

UFW is a user-friendly front-end for managing iptables firewall rules and its main goal is to make managing iptables easier or as the name says uncomplicated. Ubuntu’s firewall is designed as an easy way to perform basic firewall tasks without learning iptables. It doesn’t offer all the power of the standard iptables commands, but it’s less complex.

In this tutorial you will learn:

  • What is UFW and its Overview.
  • How to Install UFW and Perform Status Check.
  • How to Use IPv6 with UFW.
  • UFW Default Policies.
  • Application Profiles.
  • How to Allow and Deny Connections.
  • Firewall Log.
  • How to Delete UFW Rules.
  • How to Disable and Reset UFW.

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Reading local mail delivered by Postfix.

How to install postfix mail server on RHEL 8 / CentOS 8

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Postfix is a common mail server, many large distributions are shipped with Postfix installed by default. The default configuration allows local mailing only, but that in itself is very useful on a machine used by many users, and even if there is no such traffic, many services dump their reports and messages into e-mails, which is delivered to the root user locally, so the sysadmin will be noticed on any events of interest when he/she logs in and switches to root user.

A simple example would be scheduled cron jobs: any output not redirected from the output of a script running from cron will be wrapped to an e-mail and will be delivered to root‘s mailbox, so the administrator does not even have to make any effort to have the reports of the nightly backup jobs at hand.

While this standalone mode is certainly a nice service as it is, postfix is a full-fledged mail server, capable of receiving, forwarding, relaying, filtering of e-mails, it basically have every feature we need for a mail server.

In this tutorial you will learn:

  • How to install postfix on RHEL 8 / CentOS 8
  • How to verify the working service with standalone functionality.

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