🌳 Linux RHCSA → RHCE Learning Tree

1. Linux Fundamentals

1.1 What is Linux?
- Linux = Kernel + GNU tools + Shell
- Multi-user, multitasking OS
- Open-source and community driven
📘 Topic 1.2 – Linux vs Windows
- Linux is free and open-source
- Uses / (root) filesystem instead of C:\
- Case-sensitive file paths
- Text-based configuration files
- Native remote access using SSH
1.3 Linux Architecture
- User → Shell → Kernel → Hardware
- Kernel manages CPU, memory, devices
1.4 Linux Security Basics
- User & group permission model
- No default administrator login
- Strong isolation between users
1.5 SELinux Introduction
- Security-Enhanced Linux
- Mandatory Access Control
- Modes: Enforcing, Permissive, Disabled
- getenforce command
1.6 Package Management (RPM)
- RPM = Red Hat Package Manager
- Used in RHEL-based systems
- rpm -qa to list packages

2. Bash & Shell

What is Bash
Shell Prompt (# / $)
Command Structure
Pipes ( | )
Command Chaining ( ; )
History & Shortcuts
Wildcards & Globbing

3. Accessing the System

TTY & PTS
GUI vs CLI
Switching Terminals
Login & Logout
SSH Basics

4. Linux File System Hierarchy

/ , /boot , /root , /home
/bin , /sbin , /usr
/etc , /var , /dev
/opt , /tmp , /run
Absolute vs Relative Paths

5. File & Directory Management

pwd , cd
ls (all options)
touch
cp , mv
rm , rmdir
df , du

6. File Types & Links

Regular, Directory, Block, Character
Symbolic Links
Hard Links
Inodes

7. Users & Groups

Root vs Regular User
useradd, usermod, userdel
groupadd, groupdel
passwd, chage
/etc/passwd, /etc/shadow

8. Permissions & Security

chmod (numeric & symbolic)
chown, chgrp
umask
SELinux modes
Contexts & restorecon

9. Process Management

ps, top
kill, killall
nice, renice
jobs, fg, bg

10. Boot & Services

Boot Process
GRUB
systemctl
Targets
Root Password Recovery

11. Networking

IP Addressing
nmcli
ip a / ip r
hostnamectl
SSH Server

12. Storage Management

Partitions
File Systems (ext4, xfs)
mount, umount
/etc/fstab
Swap
LVM (PV, VG, LV)

13. Archiving & Transfer

tar
gzip / gunzip
zip / unzip
scp
rsync

14. Logs & Monitoring

/var/log
journalctl
log rotation

🚀 RHCE (EX294) – Automation with Ansible

Ansible Architecture
Inventory
Playbooks
Modules
Variables & Facts
Loops & Conditionals
Roles & Collections
Jinja2 Templates
Ansible Vault
Automating Services, Users, Storage

📘 Topic 1.3 – Linux Architecture

User interacts with Shell (Bash)
Shell sends commands to Kernel
Kernel communicates with hardware

📘 Topic 1.4 – Linux Security Basics

User and group permission model
SELinux provides mandatory access control
No default administrator login

📘 Topic 1.5 – SELinux Introduction

Security-Enhanced Linux (SELinux)
Developed by NSA
Modes: Enforcing, Permissive, Disabled
getenforce command to check mode

📘 Topic 1.6 – Package Management (RPM)

RPM = Red Hat Package Manager
Used in RHEL-based distributions
rpm -qa lists installed packages

🧭 Introduction to Routers: The Heart of Networking

A router is an internetworking device that connects multiple logical networks. It operates at Layer 3 (Network Layer) of the OSI model and determines the best path for data packets. In a LAN, a router usually acts as the Default Gateway, enabling internal devices to reach external networks like the internet.

⚙️ Router Hardware Components & Memory Types

Console Port (RJ45–RS232): Used for direct configuration using a terminal.
RAM: Temporarily holds the running configuration.
NVRAM: Stores the startup configuration persistently.
Flash Memory: Stores the IOS (Internetwork Operating System).

💡 Understanding Router Modes

Prompt	Mode
Router>	User Mode (limited access)
Router#	Privilege Mode (full access) — use `enable` or `en` to enter
Router(config)#	Global Configuration Mode

Other Modes

User Mode: Basic access, can’t make changes.
Setup Mode: Assists with initial configuration.
ROMmon Mode: Recovery environment used for:
- IOS recovery
- Password reset
- Flash issues
Access via: Ctrl + Pause/Break (real device) or Ctrl + C (Cisco Packet Tracer)

🧩 Types of Routers

1. Based on Platform

Hardware Routers: Cisco, Juniper, D-Link, HP, etc.
Software Routers: Microsoft Server, Linux Server

2. Based on Modularity

Fixed (Non-Modular) Routers: Non-upgradable, ports fixed to motherboard.
Modular Routers: Allow for interface upgrades using LAN/WAN cards via available slots.

EC2

EC2: Elastic Compute Cloud

AWS Budget Setup
- Root User: Billing and Cost Management > Account > Billing and Payments > IAM user and role access to Billing information: ✅ Activate IAM Access > Update
- IAM User:
  - Billing and Cost Management > Bills > Charges by service
  - Billing and Cost Management > Free Tier
  - Billing and Cost Management > Budgets > Create Budget
  - Choose budget type: Use a template (Simplified)
  - Template: Zero Spend Budget
  - Budget Name: My zero-spend budget
  - Email Recipients: mohammedimransharif@proton.me
  - Create Budget

EC2: Elastic Compute Cloud

EC2 Basics
- Amazon EC2:
- EC2 Sizing & Configuration Options:
  - Operating System (OS): Linux, Windows, or macOS
  - CPU: Compute power and number of cores
  - RAM: Memory allocation
  - Storage Options:
    - Network-attached: EBS and EFS
    - Local hardware: EC2 Instance Store
  - Network: Speed, public IP address
  - Security: Firewall rules via security groups
  - Bootstrap script: EC2 User Data
- EC2 User Data:
  - You can bootstrap instances using EC2 User Data scripts.
  - Bootstrapping: Running commands at first launch
  - Runs only once on initial startup
  - Automates boot-time tasks like:
    - Installing updates
    - Installing software
    - Downloading files
    - Custom initialization
  - Runs as the root user
- EC2 Instance Types:

Instance	vCPU	Mem (GiB)	Storage	Network Performance	EBS Bandwidth
t2.micro	1	1	EBS-Only	Low to Moderate	—
t2.xlarge	4	16	EBS-Only	Moderate	—
c5d.4xlarge	16	32	1 × 400 NVMe SSD	Up to 10 Gbps	4750
r5.16xlarge	64	512	EBS-Only	20 Gbps	13600
m5.8xlarge	32	128	EBS-Only	10 Gbps	6800

Hands-On: Create an EC2 Instance with User Data for a Simple Website

Launch an EC2 Instance running Linux
- We'll create our first virtual server using the AWS Console.
- This helps us understand the parameters involved in launching an instance.
- We'll automate setup using EC2 User Data for web server configuration.
- We'll also learn how to start, stop, and terminate the instance.
Steps:
- EC2 > Instances > Launch an instance
- Name: My First Instance
- Key Pair: Create New > Name: EC2 tutorial > Download
- Network Settings: ✅ Allow HTTP traffic from the internet
- User Data (bootstrap script):
```
#!/bin/bash
# use this for your user data (script from top to bottom)
# install httpd (Linux 2 version)
yum update -y
yum install -y httpd
systemctl start httpd
systemctl enable httpd
echo "<h1>Hello World from $(hostname -f)</h1>" > /var/www/html/index.html
      
```
- Click Launch Instance
- Go to: EC2 > Instances > ✅ Select your instance
- View Public IPv4 address > Open in browser using http://
- Note: Public IP changes on reboot; Private IP remains constant.

EC2 Instance Types Basics

Overview: Choose EC2 instances optimized for different use cases.
Ref: aws.amazon.com/ec2/instance-types
General Purpose
- Great for diverse workloads such as web servers or code repositories.
- Balanced compute, memory, and networking resources.
- t2.micro is commonly used in tutorials and free-tier setups.
Compute Optimized
- Ideal for compute-intensive tasks that require high-performance processors:
- Example: C8g
Memory Optimized
- Best for workloads that process large datasets in memory.
- Use cases:
  - Relational/non-relational databases
  - Distributed cache stores
  - In-memory BI databases
  - Real-time big data processing
- Examples: R7g, R7i, R7iz
Accelerated Computing – Uses hardware accelerators like GPUs for ML, AI, and graphics workloads.
Storage Optimized
- Optimized for high, sequential read/write access to local storage.
- Use cases:
  - OLTP systems
  - Relational & NoSQL databases
  - In-memory cache (e.g., Redis)
  - Data warehousing applications
  - Distributed file systems
- Example: i8g
Instance Features – Naming convention:
- m: instance class
- 5: generation
- 2xlarge: size within the class
To compare instances across families and specs, visit ec2instances.info

Security Groups & Classic Ports Overview

Introduction to Security Groups
- Fundamental component of AWS network security
- Control how traffic is allowed into/out of EC2 instances
- Contain only allow rules
- Rules can reference IP addresses or other security groups
Security Groups – Deeper Dive
- Act as a virtual firewall at the EC2 level
- Regulate:
  - Port access
  - IP ranges (IPv4 and IPv6)
  - Inbound traffic (external → instance)
  - Outbound traffic (instance → external)
Security Groups – Good to Know
- Can be attached to multiple instances
- Scoped to a region/VPC pair
- If traffic is blocked, the EC2 instance won't detect it
- Best practice: Use a separate security group for SSH
- If the app times out → likely security group issue
- If the app gives “connection refused” → app issue or not running
- All inbound traffic is blocked by default
- All outbound traffic is allowed by default
Common Ports
- 22 – SSH (Linux login)
- 21 – FTP (upload files)
- 22 – SFTP (secure file upload)
- 80 – HTTP (unsecured websites)
- 443 – HTTPS (secured websites)
- 3389 – RDP (Windows login)
Security Groups – Hands-On
- Go to: EC2 > Network & Security > Security Groups
- Select security group > Configure Inbound/Outbound rules
- Add, remove, or modify rules as needed
SSH Overview

AWS

What is Cloud Computing?

The Five Characteristics of Cloud Computing

On-demand Self Service
Broad Network Access
Multi-tenancy and Resource Pooling
Rapid Elasticity and Scalability
Measured Service

Types of Cloud Computing

Infrastructure as a Service (IaaS)
Platform as a Service (PaaS)
Software as a Service (SaaS)

IAM: Identity and Access Management

IAM: Permissions
- Users or groups can be assigned JSON documents called Policies.
- These policies define the permissions of the users.
- In AWS, apply the Least Privilege Principle.
IAM: Password Policy
- Multi-Factor Authentication (MFA)
How can users access AWS?
- Three options:
  - AWS Management Console
  - AWS Command Line Interface (CLI)
  - AWS Software Developer Kit (SDK)
- Access keys are generated via the AWS Console.
- Users manage their own Access Keys:
  - Access Key ID = username
  - Secret Access Key = password
- IAM > Users > stephane > Security Credentials > Access Keys > Create Access Key
AWS CloudShell
IAM Roles
- IAM > Roles > Create Role
- Trusted Entity: AWS Service ✅
- Use Case: EC2 ✅
- Add Permissions: IAMReadOnlyAccess ✅
- Role Name: DemoRoleForEC2
IAM Security Tools
- IAM Credentials Report (account-level):
  IAM > Credential Report > Download .csv file
- IAM Access Advisor (user-level):
  IAM > Users > Last Accessed
IAM Best Practices
- Don’t use the root account except for AWS account setup
- One physical user = One AWS user
- Assign users to groups and assign permissions to groups
- Create a strong password policy
- Use and enforce Multi-Factor Authentication (MFA)
- Create and use Roles for giving permissions to AWS services
- Use Access Keys for Programmatic Access (CLI / SDK)
- Audit permissions using IAM Credentials Report & IAM Access Advisor
Shared Responsibility Model for IAM
IAM Section – Summary
- Users: mapped to a physical user; has a password for AWS Console
- Groups: contains users only
- Policies: JSON document that outlines permissions for users or groups
- Roles: for EC2 instances or AWS services
- Security: MFA + Password Policy
- AWS CLI: manage your AWS services using the command-line
- AWS SDK: manage AWS services using a programming language
- Access Keys: access AWS using CLI or SDK
- Audit: IAM Credential Reports & IAM Access Advisor

Testing

Linux

🌳 Linux RHCSA → RHCE Learning Tree

Router

🧭 Introduction to Routers: The Heart of Networking

⚙️ Router Hardware Components & Memory Types

💡 Understanding Router Modes

Other Modes

🧩 Types of Routers

1. Based on Platform

2. Based on Modularity

EC2

EC2: Elastic Compute Cloud

EC2: Elastic Compute Cloud

Hands-On: Create an EC2 Instance with User Data for a Simple Website

EC2 Instance Types Basics

Security Groups & Classic Ports Overview

AWS

What is Cloud Computing?

The Five Characteristics of Cloud Computing

Types of Cloud Computing

IAM: Identity and Access Management

IAM: Identity and Access Management

IAM: Identity and Access Management