EC2 Intermediate

EC2 Intermediate

AMI

• Amazon Machine Image
• 2 different types of AMIs
  • Instance store backed AMIs
  • EBS backed AMIs.
• AMI is a container that contains snapshot, permissions and block device mapping.
  • Preconfigure an instance
  • Create an AMI that includes necessary stuff
  • Create a NEW EC2 with minted AMI.
  • By creating AMI can save time and it’s called AMI pre-baking or AMI baking.
  • Immutable architecture - means, after creation of EC2s, there is no need to change much.

ENIs etc : Network Interface related. Private Instances

• Private EC2 has ENI with private IP address.
  • Private IP addresses & Private DNS names are are static for the lifetime of the EC2 instance.
  • Multiple Private IP addresses can be there for ENI
  • Multiple ENIs can be attached to EC2.

Public Instances

• Public EC2 has ENI with public IP address.
  • They will get public IP address and DNS names.
  • They will ALSO receive private IP address and private DNS.
• You can’t apply public IP address inside the OS (of EC2 instance).
• Everything in AWS is private internally and it’s internet gateways (IGW) functionality to swap the IP addresses between
private IP and public IP address (if assigned).

Elastic IP address

• It’s for the AWS region
• If you create an EIP - you will be charged irrespective it’s attached or not.
• It’s a creation of link between private IP address to the EIP. 
When this is done, public IP address is removed and EIP (which is also) public is assigned.
• EIPs can be moved between EC2 resources.
• If you don’t want to be charged for EIP, first disassociate the EIP from EC2 and then release back to pool.

Instance ROle

• Type of IAM role that EC2 assumes.
• You don’t login to a role.
• Instance roles assume IAM roles on behalf of EC2 via an instance profile, while IAM roles can only be applied to true identities.

EC2 credentials

• Statically configured using aws configure
• Use instance IAM roles to assume
• When user needs to login, IAM roles don’t work.
• Can associate and disassociate the IAM roles on a running instance.

AWS cli credential ORDER

1. Aws [command] —profile [profile_name]
2. Environment variable like AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY and AWS_SESSION_TOKEN
3. AWS CLI credential file using ~/.aws/credentials
4. Container credentials (ECS environments)
5. Instance Profile Credentials