The shell, and why it exists.
WHAT IT IS
A program that reads what you type, runs it, and shows the result.
WHAT THAT PROGRAM IS CALLED
A shell. The common one is bash; others include sh, zsh and dash.
WHY IT STILL MATTERS
Servers have no desktop Every task is scriptable It works over a slow connection It is identical across almost every Linux system
WHAT A TERMINAL IS
The window the shell runs inside.
WHY THE DISTINCTION MATTERS
The terminal displays; the shell interprets. Problems usually belong to one or the other.
WHAT A COMMAND CONSISTS OF
The program name Options, usually preceded by one or two dashes Arguments, usually files or values
WHAT THE PROMPT TELLS YOU
Who you are Which machine Where you are Whether you are root
WHAT THE LAST SYMBOL MEANS
A hash means root. A dollar means an ordinary user.
WHY THAT MATTERS ENORMOUSLY
As root, nothing stops you deleting anything.
WHAT TO DO BEFORE RUNNING ANYTHING UNFAMILIAR
Understand what it does.
WHY
There is no undo, no recycle bin, and no confirmation for most destructive actions.
WHAT TO AVOID
Pasting commands from the internet without reading them.
