Linux tutorials, system administration, web hosting, programming

BIND (Berkeley Internet Name Domain)

botond published 2024/01/20, Sat - 07:18 time
The Linux-based BIND (Berkeley Internet Name Domain) server is the most widespread and well-known DNS (Domain Name System) software, which is a key part of the basic infrastructure of the Internet. BIND's development began at the University of Berkeley in the late 1980s, and since then it has undergone many developments to meet today's challenges. As a DNS server, BIND's main task is to translate human-readable domain names (e.g. www.pelda.hu) to IP addresses (e.g. 192.168.1.1), thus enabling Internet users to easily navigate the web. However, BIND's role is much more complex and critical than that; ensures the smooth operation of the domain name system, which is essential for the stability and security of the Internet.

POSIX (Portable Operating System Interface)

botond published 2024/01/19, p - 02:30 time
POSIX (Portable Operating System Interface) is a collection of standards created to promote compatibility between operating systems. POSIX standards are crucial in the world of software development, especially for those working with UNIX-based systems such as Linux. These standards ensure that different operating systems handle file systems, character devices, and other basic system-level functions in a similar way.

How to set and keep the exact time in sync on your Debian computer using systemd-timesyncd

botond published March 2024, 01, Thu - 18:20 time
In the world of modern information technology, the use of accurate time is a critical aspect. In today's Linux operating systems, there are many solutions to ensure that our system's clock is always synchronized with world time. In this short description, we will see how to set the date, the exact time and our time zone manually, and how to activate time synchronization with the Internet.

Make bootable flash drives with Rufus 4.3

botond published 2023. 12. 04., h - 22:18 time
Rufus is a very popular free and open source portable application for Windows operating systems that can be used to easily create bootable USB flash drives. Thanks to its active development, new editions are released regularly, which contain many new features. In this tutorial, we will try Rufus version 4.3 and use it to create a Debian 12 installation flash drive.

How to fix "554 5.7.1 Service unavailable; Client host blocked using zen.spamhaus.org; Error: open resolver;" from our server delivery of bounced letters with an error message?

botond published Jan. 2023, 03, 22:11 p.m. time
When conducting electronic correspondence, mail servers strive to filter out unsolicited mail (spam) as efficiently as possible. From time to time it happens that these spam filtering services get blocked by letters that do not contain anything that would justify this. Therefore, it may happen with us that we cannot send an email to a recipient, or that we cannot receive mail from others on our own server. In this description, we will investigate one of the more common server-side "554 5.7.1 Service unavailable; Client host blocked using zen.spamhaus.org; Error: open resolver;" type error.

Postfix

botond published Jan. 2023, 03, 22:05 p.m. time
Postfix is ​​an extremely popular free and open source MTA (Mail Transfer Agent) software developed by Wietse Venema in 1997 and first released in December 1998. Postfix aims to provide a secure and reliable mail service that is resistant to Internet attacks and spam. To this end, Postfix has a number of security features, such as traffic restriction, server and client authentication, virus and spam filtering, and content filtering.

FTP (File Transfer Protocol)

botond published 2023. 03. 20., h - 10:10 time
File Transfer Protocol (FTP) is a standard network protocol on TCP/IP networks used to transfer computer files between a client and a server. The FTP protocol was originally developed for file sharing on the Internet and plays a very important role in data transfer services to this day.

Midnight Commander (mc)

botond published 2023. 03. 20., h - 07:35 time
Midnight Commander (MC) is a text-mode file management program that is extremely popular on Linux and other Unix-like operating systems. The development of the program was started by Miguel de Icaza in 1994, and many versions have been released since then. MC allows users to easily navigate the file system and perform various operations such as copying, deleting, moving files, etc.

How to defend against attacks resulting in large volumes of 404 or other 4xx HTTP error codes with Fail2Ban

botond published 2023/03/14, k - 00:38 time
Our websites are constantly under attack from the outside world. The vast majority of these are done by robots, which try to discover the weak points of the websites running on the server. Some of the robots with this purpose try to do this by making various seemingly random HTTP requests to our websites, most of which are directed to non-existent URL addresses. As a result, our server responds with a 404 HTTP response code. In this description, we will look at how to ban the large number of attempts resulting in 404 and other 4xx HTTP response codes using Fail2Ban.