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Exercise 01 — Introduction to Linux

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Before You Start

Read Note 01 first, then come back here.

These exercises are about exploration, not memorization. The goal is to get comfortable typing commands and reading output. Every command here is safe — nothing you do in this exercise can break anything.

Open a terminal and let's begin.

Exercise 1.1 — Find Out Who and Where You Are

These are the first commands any Linux user runs on a new machine.

Step 1: Type this and press Enter:

whoami

You should see your username printed. Something like: 

jahid

Step 2: Now find out the machine's name:

hostname

Expected output (yours will differ): 

mycomputer

Step 3: Find out which Linux distro you're running:

cat /etc/os-release

This prints the contents of a file. Look for the NAME and VERSION lines. Expected output (example): 

NAME="Ubuntu"
VERSION="22.04.3 LTS (Jammy Jellyfish)"
ID=ubuntu
...

What is cat? cat reads a file and prints it to the screen. You'll use it constantly. /etc/os-release is a plain text file that your distro fills in with its own details.

Step 4: Check the kernel version:

uname -r

Example output: 

6.5.0-41-generic

Step 5: See everything at once:

uname -a

Example output: 

Linux mycomputer 6.5.0-41-generic #41-Ubuntu SMP x86_64 GNU/Linux

This shows: OS name, hostname, kernel version, build date, architecture, and OS type — all in one line.

Reflect: Write down your answers: - Distro name and version: __ - Kernel version: __ - Hostname: _____

Exercise 1.2 — Check System Time and Uptime

Step 1: Check the current date and time:

date

Example output: 

Thu Jun 20 14:32:01 UTC 2024

Step 2: Format the date as YYYY-MM-DD:

date +%Y-%m-%d

The +%Y-%m-%d part is a format string. %Y = 4-digit year, %m = month, %d = day.

Expected output: 

2024-06-20

Step 3: See how long the system has been running:

uptime

Example output: 

14:32:01 up 3 days, 4:12,  1 user,  load average: 0.08, 0.12, 0.10

Questions to answer: - How long has your system been running? - What is the load average for the last 1 minute? - How many users are currently logged in?

Exercise 1.3 — Getting Help Without Google

One of the most important skills in Linux is knowing how to get help from the terminal itself.

Step 1: Open the manual for ls:

man ls

The manual page opens. Use the arrow keys to scroll. Press q to quit.

While you're in the man page, find the answer to: What does the -a flag do?

Step 2: Get a quick one-line summary of a command:

whatis ls
whatis cp
whatis rm

Expected output: 

ls (1)  - list directory contents
cp (1)  - copy files and directories
rm (1)  - remove files or directories

Step 3: Search for commands by keyword:

apropos "disk usage"

This searches all man page descriptions. It lists every command related to "disk usage".

Example output: 

df (1)  - report file system disk space usage
du (1)  - estimate file space usage
...

Step 4: Use the quick --help flag:

mkdir --help

This prints a short summary without opening the full man page. Look for the -p flag description.

Questions: - What does mkdir -p do? (hint: you just found it) - What is the difference between man and --help?

Exercise 1.4 — Explore Your Environment

Linux stores settings in environment variables — named values that programs can read.

Step 1: See what shell you're using:

echo $SHELL

$SHELL is an environment variable. The $ prefix tells bash "give me the value of this variable". Expected output: 

/bin/bash

Step 2: See your home directory:

echo $HOME

Expected output: 

/home/jahid

Step 3: See the PATH:

echo $PATH

Example output: 

/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

PATH is a list of directories (separated by :) where Linux looks for programs when you type a command. When you type ls, Linux searches each directory in PATH until it finds a program called ls.

Step 4: List all environment variables:

env

This prints a long list. Don't worry about understanding all of them — just notice that they're all in the format NAME=value.

Exercise 1.5 — Basic Terminal Skills

Step 1: Print a message:

echo "Hello, Linux!"

Step 2: Use command substitution — run a command inside another command:

echo "Today is $(date +%A)"

The $(...) part runs date +%A first (which prints the day of the week), then echo prints the result. Expected output: 

Today is Thursday

Step 3: Run two commands on one line with &&:

whoami && hostname

&& means "run the second command only if the first one succeeded". Expected output: 

jahid
mycomputer

Step 4: View your command history:

history

Linux remembers every command you've typed. This is very useful for recalling a long command you ran earlier. To re-run a command from history, type ! followed by the line number. For example, !42 runs command number 42 again.

Step 5: Clear the terminal:

clear

Or press Ctrl + L. Your previous commands are not deleted — scroll up to see them.

Challenge — Test Yourself

Try to answer these without looking at the notes. Then check your answers.

  1. What is the difference between the Linux kernel and a distribution?
  2. What does uname -r print?
  3. You want to find commands related to the word "network". What command would you run?
  4. What does the $ at the end of your prompt mean? What does # mean?
  5. What does exit code 0 mean?

Answers: 1. The kernel is the core OS that talks to hardware. A distribution bundles the kernel with software, a package manager, and tools into a usable system. 2. The current Linux kernel version number. 3. apropos network 4. $ = regular user, # = root (administrator) 5. The command succeeded (zero means success in Linux).

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