Meet the terminal

In movies, hackers type green text into a black window. That window is the terminal, and it's less scary than it looks. You type a command, press Enter, and the computer answers.

Why type when you can click?

• Servers usually don't have a screen. Most Linux machines in the world sit in data centers with no monitor or mouse. The terminal is the only way to talk to them.
• It's faster. Something that takes ten clicks in a menu can be one line of text.
• You can repeat and automate it. You can save commands in a file and run them again, or run them on 1,000 machines at once.
• It works from far away. You can control a computer on the other side of the world over a slow connection (that's lesson 3).

The terminal is the window. The program inside it that reads your commands is called the shell. On both Rocky and Ubuntu, the shell is bash.

Reading the prompt

The text the computer shows before your cursor is called the prompt. It's the computer saying “I'm ready, what next?” It also tells you who and where you are. The two families draw it slightly differently:

• ~ (the tilde) is short for your home folder.
• $ means you're a normal user. If it ever turns into #, you're root, the all-powerful admin account, so be careful (more in lesson 12).

The parts of a command

Commands are like short sentences, and they have a grammar:

• The command is what to do. Here ls means “list.”
• Options (also called flags) change how the command works. They start with a dash: -l means “long format.” You can combine them: -l -a is the same as -la.
• Arguments say what the command works on, like a folder, a file or a website.

Five golden rules

1. Upper and lower case are different. ls works, LS doesn't. Documents and documents are two different names.
2. Spaces matter. cd .. works, cd.. doesn't.
3. No news is good news. Many commands print nothing when they work. If you get the prompt back with no error, it worked.
4. Errors are clues, not punishments. Read them. They usually tell you exactly what's wrong.
5. Commands are the same on both families. Everything in this lesson works the same on Rocky and Ubuntu. Only the prompt looks different.

Pro keyboard moves

Where do I get a real terminal?

• Windows 10/11: Open Windows Terminal or PowerShell. They include ssh, which is all you need for the next lesson. (PuTTY and other apps are covered in lesson 4.) To run real Linux inside Windows, open PowerShell as administrator and type wsl --install. That installs Ubuntu.
• Mac: Open the Terminal app. macOS isn't Linux, but it's a close cousin, and most commands here work.
• Chromebook: Go to Settings → Advanced → Developers → Linux development environment. That installs Debian.
• No computer of your own? Use the practice terminal on this site. That's what it's for.

Try it

Click in the terminal and complete the missions. You can type help at any time.

Quick check