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If you want to allow users to access specific services on your server without open a firewall, you can use port knocking. Port knocking is a method that allows you to secure your service from unauthorized users. Port knocking allows incoming connections when a correct sequence of connection attempts is received.

In this post, we will secure open SSH port 22 with port knocking. This port will only be opened when someone requests the ports 7000, 8000, 9000 in sequence.

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A mail server is very useful when you own a website or web application and want to send transactional emails to users. Postfix is a free and open-source Mail Transfer Agent used to send and receive emails. Postfix is absolutely free, so you don’t need to rely on third-party service providers like Sendgrid or Pepipost. You can easily install and configure Postfix to send emails through your local application.

In this post, we will show you how to install and configure Postfix as a Send-Only SMTP server on Ubuntu 20.04.

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Osquery is an open-source security threat monitoring tool developed by Facebook. It is used for querying system information including system version, kernel information, running processes, memory information, listening ports, login users, and more. Osquery helps system administrators to write SQL queries to identify, probe, and eliminate various types of threats. It supports several operating systems including Windows, Linux, FreeBSD, and macOS.

In this post, we will explain how to install and use Osquery on Ubuntu 20.04.

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If you are a system administrator managing a Linux server, you want a simple tool that helps to monitor your server. Darkstat is a network traffic monitoring tool that calculates and reports usage statistics sent over the HTTP server. It is a lightweight, simple, and real-time network statistics tool with an integrated webserver. Darkstat supports IPv6 protocol and asynchronous reverse DNS resolution.

In this post, we will show you how to install and use Darkstat Network Traffic Analyzer in Linux.

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Apt-Cacher NG is a caching proxy server for Debian-based Linux distributions including Ubuntu, Debian, Linux Mint, etc. It creates a local cache of the Debian mirrors and other Linux distributions. When you use the apt command to install any package, the package is pulled from the official repositories, and the APT cache server caches that package in the system. When you install the same package again, it will download that package from the local caching server. This will save you a lot of time and internet bandwidth.

In this post, we will explain how to set up an APT-Caching server using Apt-Cacher NG on Ubuntu 20.04.

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Unbound is a free, open-source, recursive, and validating DNS caching server. It uses DNS-over-TLS and DNS-over-HTTPS to encrypt connections between clients. Compared to Bind9, Unbound is lightweight and extremely fast. A caching server will help you to reduce the loading time of the website by keeping the cache database on an Unbound server. It is also capable of DNSSEC validation and can serve as a trust anchor.

In this post, we will show you how to set up Unbound DNS Resolver on Ubuntu 20.04.

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As you may be aware, CentOS has announced they will be discontinuing support for CentOS 8 on December 31, 2021 and discontinuing future development of new CentOS versions that track RedHat upstream releases.

Luckily, a new community enterprise operating system called Rocky Linux from the founder of CentOS has been introduced.

With the release of Rocky Linux 8.4, you can now easily migrate your CentOS 8 server to a fully compatible operating system that will continue to be free and fully supported for the long term.

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