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Andreas runs Anagogistis, sharing notes on Linux, networking, programming, and computer internals to better understand complex topics by breaking them down.

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Linux Networking Programming How computers work under the hood
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The author describes a frustrating issue encountered on a Linux machine (Ubuntu 24.04.2 LTS) where the 'sudo' command became slow when the VPN's kill switch engaged. The problem stemmed from the system trying to resolve the hostna...
The post clarifies the function of './' in command execution within the Bash shell, correcting inaccuracies from a previous article. It explains that Bash first checks if a command contains a '/', treating it as a pathname, and ou...
The post explains the differences between executing and sourcing a shell script in Unix-like systems. It details how the kernel processes a script with a shebang, the necessity of executable permissions, and the implications of fo...
The author reports security vulnerabilities in PureVPN's Linux clients, specifically regarding IPv6 leaks and improper firewall management. The VPN fails to restore IPv6 protections after disconnections and wipes user iptables con...
The post discusses the Year 2038 problem (Y2K38), which arises from the limitation of 32-bit signed integers used in Unix systems to represent time since the Unix epoch. It explains how this limitation leads to an overflow issue o...
The text explains the functioning of shell pipelines, emphasizing that they run concurrently rather than sequentially. It describes how the shell creates a one-way communication channel using the pipe() system call, forks two chil...
The article discusses the necessity and methods for disabling IPv6 on Linux systems, particularly to prevent VPN IPv6 leaks. It outlines common practices, including modifying the /etc/sysctl.conf file, and highlights the potential...
The post explains the differences between the 'clear' command and the 'Ctrl+L' keyboard shortcut in terminal environments. While both methods clear the visible screen, 'clear' also wipes the scrollback buffer unless the '-x' optio...
The blog post discusses the process of changing the hostname on Ubuntu, highlighting that while it can be done easily through the GUI or command line, it does not automatically update the /etc/hosts file. This oversight can lead t...
The post introduces 'et ai' as a standardized attribution for AI-assisted work, highlighting the collaborative process between humans and AI in content creation.
The article explains how to write to a root-owned file from a non-root shell by elevating privileges. It highlights the common mistake of using 'sudo echo' which fails due to shell redirection issues. The recommended solution is t...
The text explains the exec() family of functions in libc, which includes execve, execv, execvp, and others, all designed to replace the current process image with a new program. It details how these functions differ in their argum...
The text explains the organization of Linux man pages, detailing the different sections that categorize commands and functions. It outlines the purpose of each section, such as user commands, system calls, library functions, speci...
The post provides a comprehensive guide on using PGP (Pretty Good Privacy) for encrypting and signing data through public-key cryptography. It explains the process of generating a key pair, including setting up a strong passphrase...
The blog post discusses the 'yes' command in Unix-like operating systems, which outputs a specified string or 'y' indefinitely until interrupted. It highlights common uses such as automating prompts in command-line tools, stress-t...
The post provides a step-by-step guide for installing GUI applications distributed as .tar.* archives, including .tar, .tar.gz, .tar.xz, and .tar.bz2 formats. It explains how to extract the files, move the application to a standar...
The post explains how to copy and paste text between Vim and the system clipboard, highlighting that Vim uses its internal unnamed register by default. It details the use of the + register for yanking and pasting text to and from ...
The post explains how to use the reverse incremental history search feature in the GNU Bash shell by pressing Ctrl-R. It details the steps to search command history interactively, including how to navigate through previous command...

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