Linux & Bash Lab

1

Navigation & Reconnaissance

Pending

Finding Your Way

The command line is your window into the system. Learning to navigate efficiently is the foundation of all Linux skills.

# Essential navigation commands
$ pwd                    # Print Working Directory
$ ls -la                 # List all files with details
$ cd /var/log            # Change to absolute path
$ cd ..                  # Go up one directory
$ cd ~                   # Go to home directory
$ cd -                   # Go to previous directory

# Information gathering
$ whoami                 # Current user
$ id                     # User ID and group memberships
$ hostname               # System name
$ uname -a               # Kernel and system info
                

Tasks

Complete CLH-001: Intro to Hacker CLI to learn command basics
Use CLH-002: Navigation Recon to practice directory traversal
Explore the Linux Filesystem Navigator to understand the directory structure
Practice using relative vs absolute paths in the Command Simulator

CLH-001: Intro CLH-002: Navigation Filesystem Navigator Command Simulator

Practical Challenge

You've SSH'd into a new server. Write the commands you would use to: find out who you are, where you are, what's in the current directory, and what operating system is running.

2

File Operations

Pending

Working with Files

Creating, copying, moving, and deleting files are fundamental operations. Understanding these commands and their options is essential.

# Creating files and directories
$ touch newfile.txt      # Create empty file
$ mkdir -p dir/subdir    # Create nested directories

# Copying and moving
$ cp file.txt backup/   # Copy file to directory
$ cp -r dir/ newdir/    # Copy directory recursively
$ mv old.txt new.txt    # Rename file
$ mv file.txt /tmp/     # Move file to new location

# Viewing file contents
$ cat file.txt          # Display entire file
$ head -n 10 file.txt   # First 10 lines
$ tail -f /var/log/syslog # Follow log in real-time
$ less largefile.txt    # Paginated viewing

# Removing (BE CAREFUL!)
$ rm file.txt           # Delete file
$ rm -rf directory/     # Delete directory recursively (dangerous!)
                

Tasks

Complete CLH-006: File Operations for hands-on practice
Practice in Linux Lab 002: File Navigation
Understand the difference between hard links and symbolic links
Learn safe deletion practices (why rm -rf / is catastrophic)

CLH-006: Files Lab: Navigation

Safety First!

rm -rf is irreversible. Always double-check paths before executing. Consider using rm -i for interactive confirmation or trash-cli for recoverable deletion.

Scenario

You need to backup the /etc/nginx directory to /backup/nginx-$(date +%Y%m%d), then create a symbolic link /backup/nginx-latest pointing to the new backup. Write the commands.

3

Permissions & Ownership

Pending

Access Control

Linux permissions determine who can read, write, and execute files. Understanding the permission model is critical for security.

# Permission string: -rwxr-xr-x
# Breakdown: [type][owner][group][others]
# r=read(4), w=write(2), x=execute(1)

$ ls -l script.sh
-rwxr-xr-x 1 user group 1024 Dec 26 script.sh

# Changing permissions
$ chmod 755 script.sh    # rwxr-xr-x (octal)
$ chmod u+x script.sh    # Add execute for owner
$ chmod go-w file.txt    # Remove write from group/others

# Changing ownership
$ chown user:group file  # Change owner and group
$ chown -R user dir/     # Recursive ownership change

# Special permissions
$ chmod u+s /usr/bin/passwd  # SUID - run as owner
$ chmod g+s /shared/         # SGID - inherit group
$ chmod +t /tmp/             # Sticky bit - only owner can delete
                

Tasks

Complete CLH-007: Permissions to understand the permission model
Use the Permissions Calculator to convert between symbolic and octal
Understand SUID, SGID, and sticky bit security implications
Practice identifying permission issues in Linux Lab 001

CLH-007: Permissions Permissions Calculator Lab: User Identity

Security Analysis

A web server needs to: allow the webserver user to read files in /var/www, allow developers (devgroup) to read and write, and prevent everyone else from accessing. What permissions and ownership would you set?

4

Text Processing & Pattern Matching

Pending

The Power of Text

Linux treats everything as text. Mastering grep, sed, awk, and regular expressions unlocks powerful data manipulation capabilities.

# grep - pattern searching
$ grep "error" /var/log/syslog      # Find lines with "error"
$ grep -i "warning" log.txt         # Case-insensitive
$ grep -r "TODO" src/               # Recursive search
$ grep -E "^[0-9]+" file.txt        # Extended regex

# Pipelines - combining commands
$ cat access.log | grep "404" | wc -l
127

$ ps aux | grep nginx | grep -v grep

# awk - field processing
$ awk '{print $1}' access.log       # Print first column
$ awk -F: '{print $1}' /etc/passwd  # Custom delimiter

# sed - stream editing
$ sed 's/old/new/g' file.txt        # Replace all occurrences
$ sed -i 's/foo/bar/g' file.txt     # In-place edit
                

Tasks

Complete CLH-003: Pattern Hunting to master grep
Practice advanced grep techniques in CLH-011
Learn text processing with CLH-009
Understand I/O redirection with CLH-010

CLH-003: Patterns CLH-011: Advanced Grep CLH-009: Text ↔ CLH-010: I/O

Log Analysis Challenge

Write a one-liner to: find all unique IP addresses in an Apache access log, count how many requests each made, sort by count descending, and show the top 10.

5

Process Management

Pending

Managing Running Programs

Understanding processes is essential for troubleshooting and system administration. Learn to monitor, control, and investigate running processes.

# Viewing processes
$ ps aux                 # All processes with details
$ ps aux --forest        # Show process tree
$ top                    # Interactive process viewer
$ htop                   # Better interactive viewer

# Finding processes
$ pgrep -a nginx         # Find by name
$ lsof -i :80            # What's using port 80?

# Controlling processes
$ kill 1234              # Send SIGTERM (graceful)
$ kill -9 1234           # Send SIGKILL (force)
$ pkill nginx            # Kill by name

# Background processes
$ ./script.sh &          # Run in background
$ jobs                   # List background jobs
$ fg %1                  # Bring job 1 to foreground
$ nohup ./script.sh &    # Survives logout
                

Tasks

Complete CLH-004: Process Investigation
Learn process control with CLH-014
Explore the Process Management Visualizer
Understand signals and their purposes (SIGTERM vs SIGKILL)

CLH-004: Investigation CLH-014: Control Process Visualizer

Troubleshooting Scenario

A web server is unresponsive. Write the commands to: find the web server process, check its resource usage, identify if it's stuck, and restart it gracefully (or forcefully if needed).

6

Shell Scripting

Pending

Automating with Bash

Shell scripts combine commands into reusable programs. Learn to write scripts that automate repetitive tasks and solve complex problems.

#!/bin/bash
# Script structure example

# Variables
NAME="World"
echo "Hello, $NAME!"

# Conditionals
if [ -f "/etc/passwd" ]; then
    echo "File exists"
else
    echo "File not found"
fi

# Loops
for file in *.log; do
    echo "Processing: $file"
    gzip "$file"
done

# Functions
backup_file() {
    local file=$1
    cp "$file" "$file.bak"
    echo "Backed up: $file"
}

# Command substitution
TODAY=$(date +%Y-%m-%d)
HOSTNAME=$(hostname)
                

Tasks

Complete CLH-008: Shell Scripting fundamentals
Practice in the Bash Scripting Playground
Take on the CLH-015 Capstone Challenge
Explore the Command Translator for cross-platform understanding

CLH-008: Scripting Bash Playground CLH-015: Capstone Command Translator

Final Script Challenge

Write a bash script that: takes a directory as an argument, finds all files modified in the last 24 hours, backs them up to a dated archive, and logs the results. Include error handling.

Finding Your Way

Tasks

Practical Challenge

Working with Files

Tasks

Safety First!

Scenario

Access Control

Tasks

Security Analysis

The Power of Text

Tasks

Log Analysis Challenge

Managing Running Programs

Tasks

Troubleshooting Scenario

Automating with Bash

Tasks

Final Script Challenge

Linux & Bash Lab Complete!