Usefull links

Command line tools

awesome-shell

bash

scripting

bash One-Liners Explained article: Part One, Two, Three, Four, Five, Six.
bash redirections cheatsheet
bash gnu doc

sed

grymoire
wikibooks
sed1line.txt
Sed One-Liners Explained article: Part One, Part Two, Part Three.

sed grep regex

online sed editor
online regex regexper regex101
sed and regex
grep and regex
awk
grep

System

Bios / UEFI

UEFI vs BIOS explained
Grub2 ful tutorial (dedoimedo)
repair grub from live USB (techmint)
using efibootmgr command (linuxbabe)
reparer grub

Disk & partitions

tuto partitons (malekal)
créer partition (maleka)

Server

SSH

setup ssh passwordless

nginx

SSL configurator (mozilla)

Certbot with nginx

setup Certbot nginx
raspberry pi issue cert fail