Amazon Elastic Compute Cloud (EC2)

Amazon EC2 is service which provide compute capacity to AWS instances in cloud. There are two key concepts while launching instances on AWS.

The amount of virtual hardware dedicated to the instance
Software installed on the instance.

Instance Type:

C4: Compute Optimized – For workloads requiring significant processing
R3: Memory Optimized – For memory intensive Workloads
I2: Storage Optimized – For workloads requiring high amount of fast SSD storage.
G2: GPU based instances: Intended for graphics and general – purpose GPU compute workloads.

Amazon Machine Images (AMIs):

It defines initial software that will be on instance when it is launched. Which includes following:

The OS and its configuration
Initial state of any patches
Application or system software.

All AMI are based on x86 OS either on Linux or windows. There are four Sources of AMI.

AWS Published: the AMI which is published by AWS, with many versions of different OS like Ubuntu, Red Hat, Windows 2008, and Windows 2012.
AWS Marketplace: It is the online store that customer can search, buy, and independently start using software and services that run on Amazon EC2. Instance launched from AWS market place incur standard hourly cost and additional per-hour charge for additional software.
Generated from Existing Instance: An AMI can be created from an existing EC2 instance.
Uploaded Virtual Servers: Customer can create image from various virtualization formats including VHD, VMDK, and OVA. From VM import/export service.

Instance Management:

There are some methods which helps to use instance securely.

DNS Name: When instance is launched, AWS create the DNS name to access it, this DNS name is generated automatically. This DNS name persists only while instance is running and cannot be transferred to another instance.
Public IP: As soon as Instance is launched, a public ip address is assigned form AWS reserved address pool. This IP address is unique on internet and persists only while instance is running and cannot be transferred to another instances.
Elastic IP: This is unique IP address on internet that you reserve independently and associate with an EC2 instance.This IP address persists until the customer releases it and is not tied to the lifetime or state of an individual instance.

Initial Access:

Amazon EC2 used key pair for login information. Public Key to encrypt and its associated private key to decrypt. These two keys are called Key pair. It is created through AWS management Console, CLI or API or Customer can upload their own key pairs.