Thanks to virtualization, we have the ability to run another operating system within our computer’s existing operating system. This can be used for a variety of purposes, in this case I will use the free VirtualBox virtualization program for the installation, in which I will install the guest operating systems that are the subject of the tutorials. In this description, in VirtualBox running on a Linux host, I create a guest machine for Linux or Windows operating systems with a graphical desktop environment that requires more hardware resources - and therefore different settings in some places - than the previous version for Linux base systems.

The operating system running on our Debian-based web servers will become obsolete over time, so over time it will be necessary to completely upgrade the distribution. In this description, we will perform a complete upgrade of a Debian 9 (Stretch) web server to Debian 10 (Buster). There are many features on the server that will also be updated. On the first page of this description, we will perform the pre-upgrade steps to prepare your system for a secure upgrade.

If there is a major change to your Debian system - so you don't just need to upgrade one or two sub-versions - you will get an error message during a smooth upgrade:
This must be accepted explicitly before updates for this repository can be applied. See apt-secure (8) manpage for details.
This troubleshooter will fix this.

When you are not using the latest version of a Linux distribution, oddities may arise. For example, in Debian 9, you may receive a "public key not available" (NO_PUBKEY) error message when updating the backports package. We will remedy this problem in this short troubleshooter.

If you frequently use virtual machines with VirtualBox, it is a more convenient and time-saving solution if you do not create and configure a new virtual machine for each installation, but use the existing ones. In some cases, this can cause problems, such as when you try to start your installer in EFI mode, but it does not want to start. In this short little troubleshooter, we will look at how to start ISO installers on EFI mode virtual machines.

Debian 11 (Bullseye) was released on August 2021, 14, and is available in a variety of desktop environments. In this description, we will install the desktop version of KDE Plasma, using the Calamares installer in the Live version, which offers a convenient, clean and simplified installation process. This installation is performed on a 64-bit UEFI machine where the Debian 11 (Bullseye) operating system is mounted on a hard disk with a GPT partitioning scheme.

If you use external USB drives and storage devices, you can safely disconnect and disconnect them in the graphical desktop environment of your Linux system with a few clicks. Devices issued in this way will no longer be accessible, as the associated block device names will be lost and the hardware will be de-energized. By default, we can only re-use hardware by physically reconnecting it, which requires human intervention. There may be a need to still have access to our software-disconnected, turned-off storage device without having to physically unplug it and then reconnect it. If for any reason you want to be able to access your logically disconnected and unplugged USB storage device, this tutorial will look at how to restart and make available your external HDD, flash drive, or card reader without having to physically reconnect it.

When you connect an external USB drive or flash drive to your machine, the Linux system will automatically mount its file system for the appropriate user. However, this automatic mount may fail for some reason and you will get a small window with an "Not authorized to perform operation" error message.

If our locales are not set correctly or are set up after installing or updating a program, Perl-based programs will report an error. In this short guide, we will look at the solution to this error.