Seasoned Linux professionals thoroughly know data formats: it is mandatory since these formats are used by many tools as:

output format (CSV, XML, JSON, …)
the format for their settings files (YAML, TOML, XML, JSON, INI, …)
the format of the document to be sent to an API (XML by SOAP, JSON by REST)

It is straightforward that is mandatory to be familiar to Regular Expressions: many legacy tools like grep (in all of its flavours, such as egrep) and sed use them as pattern matching criteria. They should also know how to leverage on awk when a little bit of business logic is needed while processing data, and of course know most of the so called “coreutils” (sort, cut, wc, uniq, …). Modern Linux professionals are also skilled on format specific tools such as xpath and xmlstarlet (XML), jq (JSON) or yq (YAML).

In addition to that, Linux professionals should also have a thorough understanding of:

encryption technologies that guarantee data integrity and confidentiality on the disk (openssl, GPG, PGP, …)
encryption technologies that guarantee data integrity and confidentiality on the wire (TLS, X.509 certificates, Public Key Infrastructure
design patterns that exploit encryption technologies, such as Shamir’s Secret Sharing
Cryptographic API, such as PKCS#11

Honestly, in my experience, I saw too many technicians neglecting this topic, but believe me, this can be very dangerous.

OpenSSH Tutorial – The Ultimate SSH Guide To Understand It

Posted on February 14, 2023November 14, 2024 by Marco Antonio Carcano

Every system administrator daily use SSH to connect to remote systems and perform they daily tasks: the very most of the time these consist into typing statements on the terminal or copying files from and to the remote system, or again running remote commands, but SSH is much more than this: it not only provides additional facilities such as agent or forwarding, port forwarding and X11 forwarding, but it has also a subsystem that can be exploited to provide SSH secured services such as SFTP.

The goal of the "OpenSSH Tutorial - The Ultimate SSH Guide To Understand It" post is to tell you what historically drove us to SSH, describe the protocol suite in detail and provide a thorough tutorial on using all of these facilities.

SSH is a huge topic: thoroughly explaining both server and client side would require much more than a single post - actually even just explaining server side would deserve several posts. For this reason this post shows only the minimum required settings that are required server side to enable the features that are instead thoroughly described client side. In addition to that, some parts of this post are a little bit redundant, but it was the only way I found to clearly explain how things work from the client perspective and from the server perspective.

This post is based on Red Hat Enterprise Linux 9, but the same concepts apply to the very most of the Linux distributions.

Linux Console Essential – Virtual Terminals, Terminal Emulation and configuring locale

Posted on December 9, 2022November 14, 2024 by Marco Antonio Carcano

Every time you interact with a computer, either using a command line or graphically, you are using a console. Despite its ease of use, a console must address and solve a lot of compatibility problems, for example properly interpreting control characters that may differ from terminal to terminal.

Being able to customize settings such as locale and keyboard layout is the basis, but it is not enough: , having at least a basic understanding of how a console works under the hood is certainly a valuable skill that lets you quickly and easily address some uncomfortable situations that sometimes arise, especially when connecting to old systems that, in the face of security best practices, for various reasons after decades are still there without being updated, maybe because very are running obsolete services that are not compatibles with up to date operating systems.

The "Linux Console Essential Virtual Terminals Terminal Emulation and configuring locale" post is meant to provide you everything it is necessary to know to solve the most common problems that may arise concerning the Linux console and locale.

LVM Tutorial – A Thorough Howto On The Logical Volume Manager

Posted on November 9, 2022November 14, 2024 by Marco Antonio Carcano

It is almost impossible not having heard about or not having used LVM: it is one of the pillars of every Linux distribution from decades ago. Almost everyone using Linux has used it to create or modify the basic storage structures of its Linux system. The trouble is that very often people are focused on the specific task they are onto, and neglect the time to investigate its amazing features. The goal of LVM Tutorial - A thorough howto on the Logical Volume Manager is to provide an easy yet comprehensive explanation on the most interesting features of LVM that it is very likely you will need to use sooner or later.

GIT Tutorial – A thorough Git Howto About Using Remotes

Posted on September 19, 2022November 14, 2024 by Marco Antonio Carcano

Git is certainly the most popular Source Code Management (SCM) software: it is broadly used in almost every recent open source project, and even a lot of emblazoned legacy projects switched to it over the years.

In the previous post we thoroughly learned how to use it to version control sources, working only on personal - so local - repositories.

GIT Tutorial - A thorough Git Howto About Using Remotes completes our trip on learning how to professionally use Git, showing you how to link the personal local repository to shared remote bare repositories.
Knowing how to deal with this topic is of course a mandatory skill, since this is the only way you have to cooperate and work with other developers.

GIT Tutorial – A thorough Version Control with Git Howto

Posted on September 5, 2022November 14, 2024 by Marco Antonio Carcano

DevOps (and of course DevSecOps) are getting more and more adopted by companies: these methodologies rely on several frameworks and software skills, and working with a modern Source Code Management (SCM) such any kind of software implementing Git is certainly a must for every DevOps professional. This post is the first of a set of posts dedicated to Git and is aimed at providing a GIT Tutorial - A thorough Version Control with Git Howto on personal repositories, giving guidelines to proficient operating with it.
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A quick, easy yet comprehensive GPG tutorial

Posted on July 28, 2022November 14, 2024 by Marco Antonio Carcano

GnuPG is a freely available command line encryption suite based on OpenPGP encryption library, and it is probably the most used encryption suite in the world. Every IT professional sooner or later face use cases that require to know how to handle it, but the point is that, despite a trivial usage of this suite may look quite easy, there are some not so obvious nuances that if known can really improve the experience, also saving from making some hidden mistakes that can really painful if anything would go wrong.

This is a quick, easy yet comprehensive GPG tutorial with the aim to provide a quick yet thorough explanation of how to safely use this amazing encryption suite.