Sometimes, in a vast and healthy developer ecosystem of a language like Clojure, it can be difficult to know where to get started when you want to build an application. The target audience of this series is developers who have some Clojure syntax in their hands and want to start building applications.

The Pain of NixOS Beginners - Documentation and Flakes

NixOS is a highly distinctive Linux distribution built upon the Nix package manager, with a design philosophy that sets it apart from traditional distributions like Ubuntu, CentOS, Arch Linux and others.

One of NixOS's major advantages over other distributions lies in its reproducibility and declarative configuration, allowing users to replicate consistent system environments across multiple machines.

While NixOS is powerful, its strength also comes with increased system complexity. This makes it more challenging for newcomers. One major challenge is that the knowledge accumulated on other Linux distributions is not easily transferable to NixOS. Another is that official and community documentation is often scattered and outdated. These issues have troubled many NixOS beginners.

One can observe these issues with the experimental feature of the Nix package manager called Flakes. Inspired by package managers like npm and Cargo, Flakes uses flake.nix to record all external dependencies and flake.lock to lock their versions. This significantly enhances the reproducibility and composability of the Nix package manager and NixOS configurations.

Flakes' advantages have made it widely popular within the community: according to official surveys, over half of the new Nix repositories created on GitHub now utilize Flakes.

However, to maintain stability, the official documentation covers barely any Flakes-related content. This has left many Nix/NixOS users feeling confused. They see everyone using Flakes and want to learn it too, but find nowhere to start, often having to piece together scattered information, search through Nixpkgs source code, or seek help from more experienced users.

The Grand Unified Theory of Documentation
– David Laing

There is a secret that needs to be understood in order to write good software documentation: there isn’t one thing called documentation, there are four.

They are: tutorials, how-to guides, technical reference and explanation. They represent four different purposes or functions, and require four different approaches to their creation. Understanding the implications of this will help improve most documentation - often immensely.

• Tutorials - Learning oriented
• How-to guides - Problem oriented
• Explanation - Understanding oriented
• Reference - Information oriented

Sie wollen oder müssen Architektur dokumentieren und möchten dafür grafische Darstellungen verwenden? Sie wünschen sich verständliche Diagramme, die auch zukünftig noch leicht änderbar sind? Sie möchten, dass Ihre Diagramme für unterschiedliche Zielgruppen nützlich sind? Und wenn Sie ganz ehrlich sind, wollen Sie dieses Doku-Zeugs in möglichst kurzer Zeit erledigen, damit Sie sich wieder anderen Dingen zuwenden können.

This text exists mainly so that I paste the URL into the #mysql channel in Libera IRC.

The mysqldump tools allows you to convert a MySQL database server or individual schemas back to SQL. You are left with a script that is supposed to be loadable into a target server and gives you back the full database, including all objects in it.

Webseiten setzen nicht nur Cookie für sich selbst sondern gerade Webseiten mit Werbung binden Inhalte von anderen URls ein, die ihrerseits auch Cookies setzen. Diese "Unart" macht Internet-Benutzer quasi gläsern und seit 2018 haben Gesetzte die Betreiber gezwungen, sich das Einverständnis zu holen (Cookie-Banner). Mittlerweile erlauben aber auch normale Browser ohne AddOns so genannte "3rd Party Cookies" zu blocken. Das funktioniert aber nicht immer, denn auch kommerzielle Produkte binden heute zusätzlichen Code von anderen Webseiten ein. Dazu gehört z.B. auch Microsoft Teams.

Für dieses Tutorial habe ich eine Installation mit Debian 11.1 (Bullseye) verwendet. Auf dem Host existieren die beiden User Alice und Bob, welche für die Nutzung von rootless-Podman vorbereitet werden.

Die Einrichtung von rootless-Podman unter Debian Bullseye

Rootless-Container haben die Eigenschaft, dass sie in User Namespaces (siehe user_namespaces(7) und namespaces(7)) ausgeführt werden. UIDs und GIDs, welche innerhalb des Containers existieren, werden dabei auf UIDs/GIDs des Hosts abgebildet. So besitzt ein Prozess, welcher innerhalb eines Containers mit der UID 0 (root) läuft, außerhalb des Containers bspw. die UID 165537 und damit die Rechte eines normalen Benutzers.

Mit den XBee Modulen können verschiedene Netzwerkarchitekturen aufgesetzt werden. Ich verwende nur eine direkte Verbindung zwischen den beiden Modulen. Dieser Verbindungstyp ist voreingestellt und funktioniert auf Anhieb mit den XBee Pro Modulen. Natürlich kann man hier noch eigene Einstellungen vornehmen wie der Name der Verbindung bzw. das Netzwerkes heißen soll. Das empfiehlt sich wenn mehrere XBee / ZigBee Netzwerke in direkter Nähe zueinander betrieben werden. Ich benötige die Datenübertragung zwischen meiner Basistation und der mobilen Einheit für die genaue differential GPS Positionierung mit der RTK Bibliothek meines Roboters.

Als erstes werden einfach die XBee Pro Module auf die XBee Explorer USB Adapter gesetzt und via USB-Kabel am Raspberry Pi angeschlossen. Ich habe meine beiden Module jeweils an die Basistation und an die mobile Einheit angeschlossen.

NOTE: This solution should only be used in non-production environments as a method to get familiar with Ansible. For production use, I recommend installing Ansible on a dedicated Linux server.

An automated deployment tool is a must have for any IT environment. In my lab, that’s Ansible. I’ve used Ansible in my lab to automate VM deployment/destruction, adding SSH keys for remote access to my servers, joining/leaving AD domain, and monitoring the newly deployed VMs. This is very useful as I frequently deploy/destroy VMs for testing a specific use case.

For a Windows admin, Ansible can seem daunting… For one, it runs on linux. Second, it’s based off of Python. I’m here to tell you, it’s not that difficult. In fact, did you know that Ansible is one of the few configuration management tools out there that can easily/natively use PowerShell code?

In this post, I’m going to review the steps involved in getting Ansible installed & running on Windows Server 2019. While install times may vary due to lab resources and internet speed, I’m able to complete the steps outlined below for installing Ansible in a little over 20 minutes.

I have been using the awesome window manager for 10 years. It is a tiling window manager, configurable and extendable with the Lua language. Using a general-purpose programming language to configure every aspect is a double-edged sword. Due to laziness and the apparent difficulty of adapting my configuration—about 3000 lines—to newer releases, I was stuck with the 3.4 version, whose last release is from 2013.

It was time for a rewrite. Instead, I have switched to the i3 window manager, lured by the possibility to migrate to Wayland and Sway later with minimal pain. Using an embedded interpreter for configuration is not as important to me as it was in the past: it brings both complexity and brittleness.

• i3-companion
• dunst
• polybar
• picom
• rofi
• xss-lock
• inputplug
• Redshift

Network booting is cool. Once you have setup everything you can stop juggling iso images in your virtual machine configs. Instead you just kick a network boot and pick whatever you want install from the boot menu delivered by the boot server.

This article is not about the basics of setting up a boot server. The internet has tons of tutorials on how to install a tftp server and how to boot your favorite OS from tftp. This article will focus on configuring network boot for libvirt-managed virtual machines.

I like to use Makefiles. I like to use Makefiles in Java. I like to use Makefiles in Erlang. I like to use Makefiles in Elixir. And most recently, I like to use Makefiles in Ruby. I think you, too, would like to use Makefiles in your environment, and the engineering community would benefit if more of us used Makefiles, in general.

These are answers to frequently asked questions on channel #bash on the freenode IRC network. These answers are contributed by the regular members of the channel (originally heiner, and then others including greycat and r00t), and by users like you. If you find something inaccurate or simply misspelled, please feel free to correct it!

All the information here is presented without any warranty or guarantee of accuracy. Use it at your own risk. When in doubt, please consult the man pages or the GNU info pages as the authoritative references.

BASH is a BourneShell compatible shell, which adds many new features to its ancestor. Most of them are available in the KornShell, too. The answers given in this FAQ may be slanted toward Bash, or they may be slanted toward the lowest common denominator Bourne shell, depending on who wrote the answer. In most cases, an effort is made to provide both a portable (Bourne) and an efficient (Bash, where appropriate) answer. If a question is not strictly shell specific, but rather related to Unix, it may be in the UnixFaq.

This FAQ assumes a certain level of familiarity with basic shell script syntax. If you're completely new to Bash or to the Bourne family of shells, you may wish to start with the BashGuide.

More advanced users may wish to read BashPitfalls and BashProgramming.

If you want to help, you can add new questions with answers here, or try to answer one of the BashOpenQuestions.

Chet Ramey's official Bash FAQ contains many technical questions not covered here.

The famous ISP-style mail server tutorial lives here. Learn how to set up your own fully-functional mail server using Postfix, Dovecot IMAP/POP3 and MySQL backend on a Debian server just like your favorite mail or website hosting provider. This guide is a voluntary project with no profit in mind. Go ahead and learn to run your own mail server within hours.

But there is a major issue with both Signal and WhatsApp: Your account is tied to your phone number.

s I plan to move from a proprietary calendaring to a more „ressource-aware” open source solution, I decided to give Radicale a try. It is open source, appears to be rather pragmatic in its approach to „standards” and has a small footprint in regards to system requirements.

With me running Debian 8 on my server, I decided to stick with the available package and not install „from source”. So a quick „apt-get install radicale” took care of installing the necessary software (do not forget to enable the Radicale daemon in /etc/default/radicale).

The configuration of Radicale is rather straightforward and simple. In regards to transport security, You can reuse an existing TLS certificate (or get a new one from Let’s encrypt). For authentication, you can choose between several options. As I don’t have an LDAP server (yet) and I didn’t want to create a .httpasswd entry for each user, I chose „IMAP”. So Radicale will validate all credentials against the local IMAP server (Dovecot in my case).

In this post I will explain how to transfer a multi terabyte size database between two MySQL instances using mydumper, which is a logical backup and restore tool that works in parallel. I will also cover the case where you need to transfer only a subset of data.

Big tables are often problematic because of the amount of time needed to do mysqldump/restore which is single threaded. It is not uncommon for this type of process to take several days.

n a perfect world, one would upgrade databases one version at a time and not let them get too old. But our databases are where the “crown jewels” are. They must stay up 24×7. When performance is acceptable, it’s acceptable, and sometimes old versions stay around too long. We don’t live in a perfect world. This idea applies to so many things. There’s almost never a perfect data model. There is always some type of resource constraint be it storage, memory, CPU, IOPS, or just plain dollars.

I will bring this concept of not living in a perfect world into a discussion about upgrades.

Ideally there would be…

• …time to do two upgrades. One upgrade to 5.6, the other to 5.7. This is the way sane, normal people upgrade.
• …a lot of extra hardware. It sure would be nice to maybe combine a maintenance like this with a hardware refresh so that we could just have an entirely new MySQL 5.7 database shard, slap a MySQL 5.6 box in the middle as a relay, and once things are all caught up just do a VIP cutover to new machines.

The extra hardware idea I have actually worked with in the past. A client of a company I worked for just had a standalone 5.5 machine with no replicants. They were able to allocate two more servers, one to be a 5.6 relay and one new 5.7 machine that would serve as a final destination. Added bonus… At the end the 5.6 server would be upgraded and left in place for a redundant machine.