Blog techniczny

Zapraszamy na naszego technicznego bloga, na którym publikujemy treści związane z pracą którą wykonujemy. Poruszamy na nim zagadnienia związane z systemami GNU/Linux, programowaniem oraz narzędziami które wykorzystujemy w naszej pracy.

Uwaga! Blog dostępny jest tylko i wyłącznie w języku angielskim.

Życzymy miłej lektury!

Ostatnio na blogu:

» Building a powerful GNU/Linux workstation with a blazingly fast storage


It's been a while since the premiere of the latest processors for the AM4 platform. That is exactly why it could be the best moment to build a powerful workstation based on this platform (as it comes to performance + stability vs. price). PCI-e 4.0 NVMEs are cheap and have successfully passed the test of time, not to mention DDR4 memory which is widely available and also relatively cheap.

It so happens that I have some AM4-based equipment left in the lab - it is a great opportunity to start a new series about building the ultimate GNU/Linux workstation from scratch.

Regalis Technologies - building AM4-based GNU/Linux workstation

Have you ever wondered what really affects the speed of your computer? Is it a CPU? Or RAM? Not at all... The perceived speed of your system depends mainly on the speed of your storage. I bet you have an intuition that the feeling of using a computer with the latest processor and an old HDD would be very bad.

I will try to demonstrate how to push the speed of mass storage to its limits using a regular home PC. I can assure you that this option is much cheaper than buying a new computer with PCIe 5.0 and what's even more important - the result is much better!

The goal of this series is to present an approach that will lead to building a stable and powerful workstation capable of achieving enormous storage speeds (~30GB/s and more).

All this using Free (as in freedom) production-ready, server grade technology - GNU/Linux.

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» Configuring the SSH client


This part of the SSH series will cover the configuration of the OpenSSH client.

Configuration sources

The ssh client obtains configuration data from the following sources (in the following order):

  • command-line options,
  • user's configuration file (~/.ssh/config),
  • global, system-wide configuration file (/etc/ssh/ssh_config).

The client will use the first obtained value for each parameter. Configured options will be used not only by the ssh itself, but by a lot of other tools as well. That is, among others: scp, sftp, sshfs, git, ansible and any other tool which uses the OpenSSH library/suite.

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» Using SSH - the right way



The Secure Shell Protocol (SSH) is probably the most used protocol by devops/sysadmins around the world.

Most people think of the SSH as a method of accessing a shell on a remote host. The fact is that this is just one tiny usage example of the SSH. Some other examples include:

  • local port forwarding - connections to the given TCP port or Unix socket on the local (client) host are to be forwarded to the given host and port, or Unix socket, on the remote side.
  • remote port forwarding - connections to the given TCP port or Unix socket on the remote (server) host are to be forwarded to the local side,
  • local dynamic application-level port forwarding (SOCKS proxy),
  • remote dynamic application-level port forwarding (SOCKS proxy),
  • tunnel device forwarding between the client and the server (L3 tun device) - Virtual Private Network (VPN) tunnelling using the tun network pseudo-device, allowing two networks to be joined securely,
  • accessing and/or mounting a remote filesystem.

Being familiar with all the above features is absolutely essential for any SSH user - both for the sake of convenience and for the security.

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» Steganography - brief introduction


In this article, I will introduce the interesting field of steganography. My goal is to show the basics of steganography and to present a few techniques that will allow you to write clean, simple and, yet powerful program.

What is steganography

Steganography is a practice of concealing a message within another message (or a physical object) in such a way, that the message does not attract attention to itself as an object of scrutiny.

Whereas cryptography is the practice of protecting the content of a message alone, steganography is concerned with concealing the fact that a secret message is sent.

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