Summary: https://www.udemy.com/course/aws-certified-cloud-practitioner-new/learn/lecture/20260612

• Contents:

Refresher: Intro to EC2

Amazon EC2 (Elastic Compute Cloud) 101

EC2 Instance - Key Concepts

Ref: https://www.udemy.com/course/aws-certified-cloud-practitioner-new/learn/lecture/20055638

• 🔧 Instance = Virtual Machine (VM) = Virtual Server (VS)
  • Hosted inside an EC2 host (physical HW)
  • Deployed inside a VPC subnet, in a single AZ
  • You have OS-level control
• Configurations
  • Operating System (OS): Linux, Windows, MacOS
  • Type: general purpose, compute optimized, memory optimized, storage optimized, accelerated computing…
  • Size (CPU + RAM)
  • Storage: HW-internal (Instance Store) or NW-external (EBS - Elastic Block Store)
  • EC2 User Data: bootstrap code script executed when the instance is launched
    • ❗ Never executed again in that instance after launch
  • EC2 Instance Role: IAM role → IAM permissions the instance gets (when assuming role) to perform actions in other AWS resources and services
  • ENI (Elastic NW Interface): instance IP addresses in the NW
    • Security via VPC Security Groups (SGs) = firewalls

Secure Shell (SSH) Protocol

Ref: https://www.udemy.com/course/aws-certified-cloud-practitioner-new/learn/lecture/20055692 and https://www.udemy.com/course/aws-certified-cloud-practitioner-new/learn/lecture/20244642

• 🔧 Secure protocol to start a Shell CLI terminal in a remote host
  • 💡 Shell = a Linux CLI terminal
  • SSH runs on TCP port 22
• Can create SSH keys for an EC2 instance
  • Allows logging in an EC2 instance and open a Shell CLI inside it → management
  • Linux & MacOS machines can natively connect to an EC2 instance via SSH
  • Windows machines may need PuTTY if Windows OS < Windows 10
• Instance Connect → Connect to instance via SSH within your browser
  • No need to create and download SSH keys
  • ❗ Works out-of-the-box only with Amazon Linux 2

EC2 Purchasing Options

Ref: https://www.udemy.com/course/aws-certified-cloud-practitioner-new/learn/lecture/20055756

1. Shared Host (Default): your instances are hosted in the same host/HW as instances from other customers (but instances from different customers are isolated from each other)
   1. On-Demand instances (Default): predictable pricing (pay-per-second), no discounts, aimed for short and uninterrupted workloads
   2. Spot instances: launched on extra EC2 capacity, can reach very high discounts (very cheap), aimed for short workloads that can be interrupted (instances will shut down if EC2 spare capacity is gone)
      • ‼️ Workloads can be interrupted!! → Not suitable for web servers or DBs!
        • Unreliable execution time → a job can take long to complete if EC2 capacity is low
   3. Reserved instances: commit to run instances for 1 or 3 years, get discounts for your commitment, can choose full/partial/no upfront payment, aimed for long and uninterrupted workloads
      • Convertible reserved instances: unlike standard reserved instances, you can change EC2 instance type, family, OS, scope and tenancy with convertible reserved instances
   4. Capacity reservations: reserve capacity in a specific AZ or region for any duration
      • Makes sure that your business will have the allocated capacity, even if EC2 capacity is very low → useful in e.g. Christmas with sales traffic peaks
      • ❗ Does NOT provide discounts on instance fees, it only guarantees available capacity/UX performance for your business
      • Types:
        • Zonal reservations → in a specific AZ, has high priority
        • Regional reservations → in a specific region (AZ can be changed, has lower priority)