fix: fix linter problems (#1633)

- nested list
- list
- trailing whitespaces
- remove $ on online command (no return) as suggested by linter
I also add the markdown extension keys (++ctrl+a++). It could be better for us to use pure markdown (to test in pdf to see how it's rendering)

docs/books/admin_guide/00-toc.md

@@ -1,6 +1,7 @@
 ---
 title: Learning Linux With Rocky
 ---
+<!-- markdownlint-disable MD025 MD007 -->
 
 # Learning Linux with Rocky
 
@@ -22,6 +23,4 @@ Backup and Restoration is essential info for the System Administrator. Linux com
 
 System Startup is also an important read because management of the system during the boot process has evolved significantly in recent years since the arrival of the systemd.
 
-
 Final chapters address Task Management, Implementing the Network, and Software Management including installation.
-

docs/books/admin_guide/01-presentation.md

@@ -1,6 +1,7 @@
 ---
 title: Introduction to Linux
 ---
+<!-- markdownlint-disable MD025 MD007 -->
 
 # Introduction to the Linux Operating System
 
@@ -10,15 +11,16 @@ In this chapter you will learn about GNU/Linux distributions.
 
 **Objectives**: In this chapter you will learn how to:
 
-:heavy_check_mark: Describe the features and possible architectures of an operating system.   
-:heavy_check_mark: Recount the history of UNIX and GNU/Linux.   
-:heavy_check_mark: Choose the right Linux distribution for your needs.   
-:heavy_check_mark: Explain the philosophy of Free and Open-source Software.   
-:heavy_check_mark: Discover the usefulness of the shell.   
+:heavy_check_mark: Describe the features and possible architectures of an operating system.  
+:heavy_check_mark: Recount the history of UNIX and GNU/Linux.  
+:heavy_check_mark: Choose the right Linux distribution for your needs.  
+:heavy_check_mark: Explain the philosophy of Free and Open-source Software.  
+:heavy_check_mark: Discover the usefulness of the shell.
 
 :checkered_flag: **generalities**, **linux**, **distributions**
 
-**Knowledge**: :star:    
+**Knowledge**: :star:
+
 **Complexity**: :star:
 
 **Reading time**: 10 minutes
@@ -36,13 +38,19 @@ Linux, UNIX, BSD, Windows, and MacOS are all **operating systems**.
 As part of this management of resources, the operating system has to:
 
 * Manage the **physical** or **virtual** memory.
+
     * The **physical memory** is made up of the RAM bars and the processor cache memory, which are used for the execution of programs.
+
     * The **virtual memory** is a location on the hard disk (the **swap** partition) that allows the unloading of the physical memory and the saving of the current state of the system during the electrical shutdown of the computer.
+
 * Intercept **access to peripherals**.
   Software is rarely allowed to access hardware directly (except for graphics cards for very specific needs).
+
 * Provide applications with proper **task management**.
-  The operating system is responsible for scheduling processes to occupy the processor.
+  The operating system is responsible for scheduling processes to occupy the processor
+
 * **Protect files** from unauthorized access.
+
 * **Collect information** about programs in use or in progress.
 
 ![Operation of an operating system](images/operating_system.png)
@@ -113,12 +121,17 @@ Linux equips 100% of the top 500 supercomputers since 2018. A supercomputer is a
 ### Architectural design
 
 * The **kernel** is the first software component.
+
     * It is the heart of the Linux system.
     * It manages the hardware resources of the system.
     * The other software components must go through it to access the hardware.
+
 * The **shell** is a utility that interprets user commands and ensures their execution.
+
     * Main shells: Bourne shell, C shell, Korn shell and Bourne-Again shell (bash).
+
 * **Applications** are user programs including but not limited to:
+
     * Internet browsers
     * Word processors
     * Spreadsheets
@@ -161,8 +174,8 @@ Linux is based on recognized standards such as [POSIX](http://en.wikipedia.org/w
 * Value portability.
 * Do one thing and do it well.
 * KISS: Keep It Simple Stupid.
-* "UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity." (__Dennis Ritchie__)
-* "Unix is user-friendly. It just isn't promiscuous about which users it's friendly with." (__Steven King__)
+* "UNIX is basically a simple operating system, but you have to be a genius to understand the simplicity." (**Dennis Ritchie**)
+* "Unix is user-friendly. It just isn't promiscuous about which users it's friendly with." (**Steven King**)
 
 ## The GNU/Linux distributions
 
@@ -176,7 +189,7 @@ This principle allows distributions to be geared to **beginners** (Ubuntu, Linux
 
 There are many graphic environments such as **GNOME**, **KDE**, **LXDE**, **XFCE**, etc. There is something for everyone, and their **ergonomics** hold their own against Microsoft or Apple systems.
 
-So why is there so little enthusiasm for Linux, when this system is practically **virus free**? Could it be because so many editors (Adobe) and manufacturers (Nvidia) do not play the free game and do not provide a version of their software or __drivers__ for GNU/Linux? Perhaps it's fear of change, or the difficulty of finding where to buy a Linux computer, or too few games distributed under Linux. That last excuse at least shouldn't be true for long, with the advent of the game engine Steam for Linux.
+So why is there so little enthusiasm for Linux, when this system is practically **virus free**? Could it be because so many editors (Adobe) and manufacturers (Nvidia) do not play the free game and do not provide a version of their software or **drivers** for GNU/Linux? Perhaps it's fear of change, or the difficulty of finding where to buy a Linux computer, or too few games distributed under Linux. That last excuse at least shouldn't be true for long, with the advent of the game engine Steam for Linux.
 
 ![GNOME Desktop](images/01-presentation-gnome.png)
 
@@ -254,62 +267,62 @@ There are several types of shells available and configurable on a platform or ac
 
 :heavy_check_mark: An operating system is a set of programs for managing the available resources of a computer:
 
-- [ ] True   
-- [ ] False
+* [ ] True  
+* [ ] False
 
 :heavy_check_mark: The operating system is necessary to:
 
-- [ ] Manage physical and virtual memory   
-- [ ] Allow direct access to peripherals   
-- [ ] Subcontract the management of tasks to the processor   
-- [ ] Collect information about the programs used or in use   
+* [ ] Manage physical and virtual memory  
+* [ ] Allow direct access to peripherals  
+* [ ] Subcontract the management of tasks to the processor  
+* [ ] Collect information about the programs used or in use  
 
 :heavy_check_mark: Among these personalities, which ones participated in the development of UNIX:
 
-- [ ] Linus Torvalds   
-- [ ] Ken Thompson   
-- [ ] Lionel Richie   
-- [ ] Brian Kernighan   
-- [ ] Andrew Stuart Tanenbaum   
+* [ ] Linus Torvalds  
+* [ ] Ken Thompson  
+* [ ] Lionel Richie  
+* [ ] Brian Kernighan  
+* [ ] Andrew Stuart Tanenbaum  
 
 :heavy_check_mark: The original nationality of Linus Torvalds, creator of the Linux kernel, is:
 
-- [ ] Swedish   
-- [ ] Finnish   
-- [ ] Norwegian   
-- [ ] Flemish   
-- [ ] French  
+* [ ] Swedish  
+* [ ] Finnish  
+* [ ] Norwegian  
+* [ ] Flemish  
+* [ ] French  
 
 :heavy_check_mark: Which of the following distributions is the oldest:
 
-- [ ] Debian   
-- [ ] Slackware   
-- [ ] Red Hat   
-- [ ] Arch
+* [ ] Debian  
+* [ ] Slackware  
+* [ ] Red Hat  
+* [ ] Arch
 
 :heavy_check_mark: Is the Linux kernel:
 
-- [ ] Multi-tasking   
-- [ ] Multi-user   
-- [ ] Multi-processor   
-- [ ] Multi-core   
-- [ ] Cross-platform   
-- [ ] Open   
+* [ ] Multi-tasking  
+* [ ] Multi-user  
+* [ ] Multi-processor  
+* [ ] Multi-core  
+* [ ] Cross-platform  
+* [ ] Open  
 
 :heavy_check_mark: Is free software necessarily open-source?
 
-- [ ] True   
-- [ ] False   
+* [ ] True  
+* [ ] False  
 
 :heavy_check_mark: Is open-source software necessarily free?
 
-- [ ] True   
-- [ ] False   
+* [ ] True  
+* [ ] False  
 
 :heavy_check_mark: Which of the following is not a shell:
 
-- [ ] Jason   
-- [ ] Jason-Bourne shell (jbsh)   
-- [ ] Bourne-Again shell (bash)   
-- [ ] C shell (csh)   
-- [ ] Korn shell (ksh)   
+* [ ] Jason  
+* [ ] Jason-Bourne shell (jbsh)  
+* [ ] Bourne-Again shell (bash)  
+* [ ] C shell (csh)  
+* [ ] Korn shell (ksh)