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Tejas Jain - AWS Notes #1

AWS Organizational Hierarchy AWS Organizations "must" be the starting point of your AWS deployment. (unless you are absolutely sure that it won't scale.. highly unlikely!!)



An AWS Organization comprises of multiple "Organizational Units (OUs)". OUs comprise of other OUs or member "AWS Accounts". 



Image credits : Here

Tip : Design the OUs such that they complement with your organizational hierarchy and businesses and sub-divisions.

For eg. 
Company XYZ maps to an AWS Organization, 
   -- Finance maps an OU, 
      --  Investment Banking within Finance maps to a sub-OU
            -- Investment Banking Prod environment maps to an AWS Account
            -- Investment Banking Non-Prod environment gets another AWS Account
            -- Investment Banking Dev environment gets another AWS Account
      --  Fixed Income within Finance maps to another sub-OU
      --  Retail within Finance maps to another sub-OU
        and so on...
 
OUs inside another OU are termed as "nested OUs"


Image credits : Here

Breaking down AWS Organizations further:

1. Organization : 
    An entity that consolidates multiple AWS Accounts, and used to administer the accounts as a single unit.
    An Organization has one management account along with zero or more member accounts.

2. Root:
    Parent container
    Applying a policy to the root, applies the policy to all the OUs and accounts in the Organization
    You can have only one root

3. Organizational Unit:
    Container for AWS accounts or other OUs
    A policy attached to an OU is applied to all the member accounts / sub-OUs under it
    One parent only per OU
   
4. AWS Account
    It contains AWS resources and identities that can access these resources

5. Service Control Policy (SCP)
      It is a document that describes controls to be attached to the              entire organization, OU or individual AWS accounts
      It contains policies that define the services and action that users or a role can perform
      Policies are inherited and assigned at different points in the hierarchy
        Similar to IAM permission policies except that they don't grant permissions.
        Two strategies for SCPs
            1. Allow list strategy -- By default, access is allowed
            2. Deny list strategy

Management Account
1. Create accounts in the organization (Greenfield deployments)
2. Invite other existing accounts to the organization (think mergers & acquisitions)
3. Remove accounts from the organization (Divestitures -- company selling one of its business units)
4. Manage Invitations 
    The process of asking another account to join your organization
    This can be done only via the "management account"
    Invitation is provided to an Account ID or email address
    The invited account, after accepting invitation becomes a "member account"
    


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