Linux tutorials, system administration, web hosting, programming

CIDR (Classless Inter-Domain Routing)

botond published 2023/03/14, k - 00:28 time
CIDR (Classless Inter-Domain Routing) is a network protocol that enables more efficient use of the network addressing system on the Internet and other networks. CIDR was created to overcome the limitations of the traditional classful addressing system.

HTTP/2 (protocol)

botond published 2023/03/14, k - 00:11 time
HTTP/2 (HyperText Transfer Protocol / 2) is a protocol that is an improved version of the HTTP/1.1 protocol, released by the HTTP Working Group in 2015. HTTP/2 is supported by most modern browsers and allows web pages to load faster than previous versions.

How to fix "dovecot: master: Error: socket() failed: Address family not supported by protocol" errors

botond published 2023/02/25, Sat - 08:03 time
After updating ISPConfig, not all services restarted. In this case, the Dovecot POP3/IMAP mail server and even Postfix threw warnings. Although we fixed these errors earlier, our settings were overwritten again during the ISPConfig update. In this troubleshooter, on the one hand, we fix "Address family not supported by protocol" type errors that cause the service to be inoperable, and we also make their permanent settings so that they remain even after further ISPConfig updates.

How to upgrade our perfect server based on Debian 10 (Buster) to Debian 11 (Bullseye)

botond published 2023/01/31, k - 11:10 time
Another era has come again, when our Debian 10 (Buster) server has also run out of time, and it has become a burning task to do something about this problem. In this tutorial, we will upgrade a perfect Debian 10 (Buster) server to Debian 11 (Bullseye). On this page, we review the necessary tasks before the update, which we use to prepare our system for the new main version.

Server monitoring with Monit on Debian and Ubuntu systems

botond published March 2023, 01, Thu - 26:02 time
Monit is a free and open source process and resource monitoring tool that can be used to monitor system processes and resources using a web browser and command line. Monit automatically stops or restarts processes or services if, for example, they use too many resources or behave abnormally. It also sends email alerts about various events.
On this page, we install the Monit system monitor program on a Debian 10 (Buster) perfect server version 1.1, where it was not used before, and then set it up.

How to set the default website on our ISPConfig server so that the Apache2 Debian Default page is not loaded when accessing the server's IP address or full hostname

botond published 2023/01/21, Sat - 00:20 time
Our ISPConfig server handles our websites nicely, however, if we refer to the server's IP address or full hostname in the browser, we do not get the expected result, because in this case the Apache2 Debian Default Page is loaded, which is essentially Apache's "welcome" page. Of course, this is not a tragic mistake, but a beauty mistake. In this description, we will see how we can configure our Apache web server so that the website we want is loaded.

How to build and arming our ISPConfig3 server and how to secure our control panel, main services and websites with Let's Encrypt SSL

botond published 2023/01/20, p - 23:14 time
With the help of the ISPConfig control panel, we can easily manage the websites on our server, as well as other web services. In this description, we will review how to build and provision our ISPConfig3 server, as well as how to set up free SSL certificates issued by Let's Encrypt for the control panel, main services and our websites. On this page, we will install the basic system, the ISPConfig control panel with the necessary components, and then check the existing web interfaces and services.

PTR record

botond published March 2023, 01, Thu - 19:21 time
DNS connects domain names (domain names) to IP addresses. The DNS PTR record, otherwise known as the pointer record, provides the domain name associated with the IP address. A DNS PTR record is the exact opposite of an "A" record, which specifies the IP address associated with a domain name.
When a user tries to access a domain name in their browser, a DNS lookup occurs in the background, where the system looks for the IP address associated with the domain name. And DNS PTR records are used in reverse DNS lookups, which is the exact opposite of the normal DNS lookup process: it's a query that starts with an IP address and finds the domain name associated with it.

HSTS (HTTP Strict Transport Security)

botond published 2023. 01. 09., h - 06:35 time
HSTS (HTTP Strict Transport Security) is a policy mechanism that helps protect websites from man-in-the-middle attacks, such as protocol downgrade or cookie hijacking. It allows websites to require web browsers (and other web client applications) to automatically only use HTTPS connections, which implement strong encryption using SSL/TLS. HSTS is a 2012 IETF standard defined in RFC 6797.