Lab 00: Security Fundamentals Hands-On Exercises

Objective

Explore user identity, file permissions, and environment variables to understand security concepts on your local machine.

Prerequisites

• A terminal application:
  • macOS: Terminal.app (pre-installed in Applications > Utilities)
  • Windows: Git Bash (bundled with Git for Windows)
  • Linux: Terminal (pre-installed)
• Module 02 (The Command Line) for basic terminal skills

Duration

5 to 8 minutes

Instructions

Step 1: Identify Your User Identity (~2 min)

In this step you discover which user account you are logged in as. Understanding user identity is the foundation of authentication.

Display your username:

macOS/Linux:

whoami

Expected output (your username will differ):

student

Display detailed user and group information:

id

Expected output (your IDs and groups will differ):

uid=501(student) gid=20(staff) groups=20(staff),12(everyone)

The uid is your user ID, gid is your primary group ID, and groups lists all groups you belong to. On Linux servers, these IDs determine what files and resources you can access.

Windows (Git Bash):

whoami

Expected output (your machine name and username will differ):

desktop-abc123\student

On Windows, the output includes the machine name followed by a backslash and your username.

Step 2: Examine File Permissions (~3 min)

In this step you create a file and examine its permissions. File permissions control who can read, write, and execute files.

List files with permission details:

ls -la

This shows all files in the current directory with their permissions, owner, group, size, and modification date.

Create a file with sensitive content:

echo "secret data" > secret.txt

This command produces no output.

View the file permissions:

ls -la secret.txt

Expected output (date and user will differ):

-rw-r--r--  1 student  staff  12 Jan  1 12:00 secret.txt

The permission string -rw-r--r-- breaks down as follows:

• - means this is a regular file (not a directory)
• rw- means the owner can read and write
• r-- means the group can read only
• r-- means everyone else can read only

Restrict the file to owner-only access (macOS/Linux):

chmod 600 secret.txt

This command produces no output.

Verify the updated permissions:

ls -la secret.txt

Expected output:

-rw-------  1 student  staff  12 Jan  1 12:00 secret.txt

The permission string -rw------- means the owner can read and write, and no one else can access the file.

Note for Windows users: Git Bash displays permission strings, but chmod has limited effect on Windows file systems. On Linux servers (which you will use in the bootcamp), file permissions are critical for security. The chmod 600 pattern is commonly used to protect private keys and configuration files.

Step 3: Explore Environment Variables (~2-3 min)

In this step you examine environment variables on your system. Environment variables store configuration that programs use at runtime.

Display your home directory:

echo $HOME

Expected output (your path will differ):

/Users/student

Display the PATH variable:

echo $PATH

Expected output (your paths will differ):

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

The PATH variable tells the system where to look for commands when you type them. Each directory is separated by a colon.

List the first 10 environment variables:

macOS/Linux:

env | head -10

Windows (Git Bash):

env | head

Expected output (your variables will differ):

HOME=/Users/student
USER=student
SHELL=/bin/zsh
PATH=/usr/local/bin:/usr/bin:/bin
LANG=en_US.UTF-8

Environment variables store configuration such as your username, home directory, and preferred language. In cloud computing, secrets (API keys, database passwords) should be stored in a secrets manager, not in environment variables or code. AWS Secrets Manager and AWS Systems Manager Parameter Store are designed for this purpose.

Validation

Confirm the following before moving on:

• Running whoami displays your username
• Running ls -la secret.txt shows the file with permissions
• Running echo $PATH displays a list of directories

Cleanup

Remove the file created during this lab:

rm secret.txt

If you created a working directory for this lab, remove it:

macOS/Linux:

cd ~
rm -r it-fundamentals-lab

Windows (Git Bash):

cd ~
rm -r it-fundamentals-lab

Windows (PowerShell):

cd $HOME
Remove-Item -Recurse -Force it-fundamentals-lab

No cloud resources were created during this lab. No further cleanup is needed.

Challenge (Optional)

Research what the numbers in chmod 600 mean. Hint: 6 = read (4) + write (2) for the owner, 0 = no permissions for the group, and 0 = no permissions for others. Try chmod 644 secret.txt and compare the permissions with ls -la. What changed, and who can now read the file?

AWS Bootcamp: From Novice to Architect Author: Samuel Ogunti License: CC BY-NC 4.0