When you use ssh access, your computer (client) retrieves the server's ECDSA (Elliptic Curve Digital Signature Algorithm) fingerprint each time it connects, which it stores in the list of known servers during the first connection (by default in the ~ / .ssh / known_hosts file). From now on, for future ssh connections, our machine will recognize the ECDSA fingerprint of the remote machine, verifying that we are connecting to the exact same machine later. If the newly retrieved fingerprint does not match the previously stored version during a subsequent connection, ssh throws the following error: "WARNING: POSSIBLE DNS SPOOFING DETECTED!" and "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!". These error messages alert you to the possibility that you may be a victim of DNS spoofing, or that the server's ECDSA fingerprint, that is, the public key of the SSH server, has changed.

When we run websites, our server and the websites and services that run on it are often vulnerable to external attacks, and our MySQL / MariaDB database server is no exception. If the Fail2Ban protection software is also available on your server, this short description will show you how to make your server more secure against attacks on your "Access denied for user root @ ip address (using password: YES / NO)" database server.

GRUB is a boot program that starts the selected operating system when you start your computer. For Ubuntu Linux systems, the GRUB menu will only appear by default if you have more than one operating system installed on your computer, giving the user the option to select the system they want to boot. However, sometimes you may need to display the GRUB menu for an instance of Ubuntu. In this short description, we'll look at how to bring up the GRUB menu for a single Ubuntu system.

Ubuntu 22.04 LTS (Jammy Jellyfish) was officially released on April 2022, 21, and will receive software support through LTS (Long Term Support) for another 5 years, meaning we won’t have to worry about updates coming until April 2027. The operating system includes the GNOME 42.0 desktop environment. In this description, it is installed on a 64-bit machine running UEFI, where a hard disk with a GPT partitioning scheme is used for this purpose.

In this troubleshooter, we roll up a Fail2Ban block caused by an Apache error of type "AH01630: client denied by server configuration" caused by Matomo's web analytics system. Finally, we fix the problem by modifying the Fail2Ban filter in apache-auth.

If you are running operating systems in VirtualBox, it is a good idea to install Guest Additions on the guest system, which will provide a greater degree of compatibility with the virtual hardware so that the guest system can make better use of the available hardware resources. In this description, we will install the Guest Additions package on a system with a Debian 6.1 (Bullseye) KDE desktop environment running in VirtualBox 11.

In this description we will install a Debian 11 (Bullseye) minimal server, which consists of the basic Debian 11 system and some basic program installation and configuration. The server will later serve as a basis for additional server installations. On this page we will install the base system.

VirtualBox can be installed on a variety of operating systems, including all versions of Windows. However, there are still issues with Windows 11. The current version of Virtualbox (6.1) theoretically supports Windows 11, but there are problems during installation. This troubleshooter resolves this issue so that you can install the current latest version of Windows, 11, without any problems.

In this dual boot description, we first install a Windows 11 operating system and then an instance of Ubuntu 21.10 (Impish Indri) Linux. It is installed on a 64-bit UEFI-based machine, where 64-bit systems are mounted on two partitions on a hard disk with a single GPT partitioning scheme. On this page, we'll review the prerequisites and then install Windows 11.