Linux

TTL (Time To Live) — is an eight-bit field in the IP header that defines the maximum number of “hops” (nodes) a packet can traverse before being discarded. Each time it passes through any router the TTL value is decreased by 1.

Typical default TTL values

Different operating systems use different initial values. This allows remote OS fingerprinting.

Why change TTL? Usage patterns

1. Bypassing tethering restrictions (internet sharing)

The most common scenario. Mobile carriers analyze incoming traffic.

When working on real projects (CDN change, migration, refactor) you often need to bulk-replace one URL with another.

At first glance the task seems trivial: sed -i 's|old|new|g' **/* — and done.

In reality that approach is Russian roulette.

A careless replacement leads to:

• 💀 Corruption of binary files (images, pdf, archives);
• 📉 Garbage in git history (binaries marked as changed);
• 🚫 Inability to cleanly roll back if a backup wasn’t made.

In this note we’ll cover a production-grade algorithm: change only text, don’t touch binaries, make a targeted backup.

Jitsi Meet works out of the box very well for video conferencing. The Jitsi Meet + Jibri bundle allows you to record meetings — and many installations stop there.

But as soon as Jitsi is used not occasionally, but as part of a working process, questions arise very quickly:

• Where should recordings be stored centrally?
• How can links be automatically published for the team?
• How can we get rid of heavy MP4 files and move to streaming playback?
• How can recordings be served over HTTPS without exposing the directory structure?
• How can all of this be done automatically, without manual administrator involvement?

Below is a full production pipeline with code: from Jibri finalizing a recording to publishing in Notion and asynchronous MP4→HLS transcoding with delivery via Caddy.

If I were sent to a deserted digital island and allowed to take only one networking utility — I would unhesitatingly choose Netcat.

The official documentation (man nc) dryly states: “a utility for reading from and writing to network connections using TCP or UDP.”
In practice it’s the Swiss army knife of the network engineer, replacing dozens of specialized programs.

The article uses examples for OpenBSD netcat — this is the one that ships by default in Ubuntu 20.04+, Debian 10+, Fedora, Arch, Alpine and most modern distributions.

Read more

Yocto — this is not a distribution.
It’s a tool from which you build your Linux.
Like Lego, only for engineers.

🔧 Who needs Yocto

• Developing medical or industrial devices
• Require a 10-year support lifecycle
• Want a minimal image (15 MB)
• Working at Siemens, Bosch, or Toradex

🛠 How to build your Linux

# 1. Клонируем репозиторий
git clone git://git.yoctoproject.org/poky
cd poky
source oe-init-build-env

# 2. Настраиваем
echo 'MACHINE = "raspberrypi5"' >> conf/local.conf

# 3. Собираем
bitbake core-image-minimal

The resulting image will appear in tmp/deploy/images/.

Imagine: an old router for 2000 ₽ blocks ads, shares a VPN, works as a Mesh system and doesn’t slow down even with 50 devices.
This is not magic — this is OpenWRT.

🏠 Who needs OpenWRT

OpenWRT turns an ordinary router into a mini-server. If you have at least one item from the list — it’s definitely time to try it:

• Want AdBlock for the whole house
• Need a VPN without a subscription
• Have an old router lying around
• Like to tinker with settings

90% of users install OpenWRT — and forget about the router forever.

This guide will show how to configure two Linux servers so that all the Internet traffic from a specific local subnet (for example, 10.100.10.0/24) is routed not via its default gateway but through an IPIP tunnel to a remote server, which will then put that traffic onto the Internet.

This is useful if you need services in one subnet to go out to the world with the IP address of another server — for example, to bypass restrictions, centralize NAT, or hide the source.

Hello! If you’re new to the world of remote server administration, you’re probably familiar with SSH — a reliable tool for connecting to remote machines. But what do you do when the connection is unstable: Wi‑Fi drops, you switch to mobile data, or your laptop “sleeps”? This is where Mosh (Mobile Shell) comes in — a “mobile shell” that makes remote work comfortable even in poor conditions.

In this article we’ll look at what Mosh is, why it’s better than SSH in certain scenarios, how to install and use it. Everything simple and step‑by‑step — for absolute beginners. Let’s get started!

Hello, aspiring web developer! 👋
If you’re just diving into the world of building websites, you’ve probably already heard of LAMP and LEMP. These acronyms sound like something out of a spy movie, but in reality they are the foundation of most dynamic websites you use every day.

In this article we’ll break down what LAMP and LEMP are, how they differ, where they’re used, and introduce a cool hybrid stack — the Nginx and Apache combo that brings together the best of both worlds.
Ready? Let’s go! 🚀

Introduction

If you are a beginner system administrator or developer, you’ve probably faced the task of managing network traffic. One of the most powerful tools for this is HAProxy, a high-performance load balancer for TCP and HTTP.

In this article, we will cover:

• what TCP proxying is,
• why to use HAProxy,
• a sample configuration for beginners,
• security and monitoring tips.

What is TCP Proxying?

TCP Proxying is the forwarding of TCP connections from a client to a server (or group of servers) through an intermediary. Unlike an HTTP proxy that operates at the application layer, TCP proxying happens at the transport layer, making it universal for any TCP protocol: from databases to mail services.