Infrastructure as code (CF) Flashcards by Rashell Smith

CloudFormation

CloudFormation defines logical resources within templates (using YAML or JSON).

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CloudFormation Stacks

what gets created from a CF template

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Parameters

Template parameters accept input form console ,CL, or API

when a stack is created or updated

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Template Parameters

Default, or explicit values chosen

you set the values in the template

Parameters references are used by CloudFormation to provision physical resources

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Pseudo Parameters

Parameters provided by AWS based on environment when creating the stack

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CloudFormation Intrinsic functions: Fn::GettAtt

GetATT can be used to retrieve any attribute associated with the resource. Most Logical resources return detailed configuration of the physical resources.

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CloudFormation Intrinsic Functions

AWS CloudFormation provides several built-in functions that help you manage your stacks. Use intrinsic functions in your templates to assign values to properties that are not available until runtime.

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CloudFormation Intrinsic functions: Ref

using !Ref on template or pseudo parameters returns their value. When used with logical resources-the physical ID is usually returned

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CloudFormation Intrinsic functions:

Fn::Join and Fn: Split

split or join strings

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CloudFormation Intrinsic functions:

Fn::GetAZs and Fn::Select

!GetAZs and !Select, a template can be made portable. Rather than explicitly specifying AZ by using intrinsic functions resources can be launched or created in AZ1 AZ2

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CloudFormation Intrinsic functions:

Fn::Basse64 & Fn::Sub

Fn::Base64 accepts plaintext .. and outputs Base64 encoded text

Fn::Sub substitutes variables in the input, which their actual runtime values. In the example the instanceid attribute of the instance logical resource.

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CloudFormation Conditions

created in the optional ‘conditions’ section of a template

conditions are evaluated to True or False

processed before resources are created

user the other intrinsic function AND,EQUALS,IF,NOT, OR

associated with local resources to control if they are created or not

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CloudFormation Intrinsic functions:

Fn::Cider

Fn::Cider is used to generate a number of smaller CIDR ranges for subnets, from a larger VPC range

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CloudFormation Mappings

Templates can contain a mapping object which contains may mappings which maps keys to values , allowing lookup

can have one key, or Top & second level

Mappings use the !FindInMap intrinsic function

Common use.. retrieve AMI for given region & architecture

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CloudFormation Outputs

Templates can have an optional output section values can be declared in this section visible as outputs when using CLI or console UI.

accessible from a parent stack when using nesting. can be exported , allowing cross-stack references.

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CloudFormation DependsOn

Depends on let you explicitly define the dependency order

ex: if resources B and C depends on A both wait for A to complete before starting

CloudFormation Wait Condition, Creation Policy & cfn-signal

configure CloudFormation to hold → wait for ‘x’ number of success signals

wait for Timeout H:M:S for those signals(12hr Max)

can send success or fail signals

EC2 and to scaling groups(AWS resouces) → user a creationPolicy

EC2 or external Systems → used to get information from external system

CloudFormation Nested Stacks

used to overcome the 500 resource limit of one stack

modular template .. code reuse

Make the installation process easier

nested stack created by the root stack

you can only refence the outputs when using nested stacks you can’t reference the logical resources created in any of the nested stack

CloudFront Cross-Stack References

outputs are normally not visible from other stacks

Nested stacks can reference them

outputs can be exported… Making them visible from other stacks

Exports must have a unique name in the regions

Fn::Import can be used instead of Ref

CloudFormation StackSets

Deploy CFN stacks across many account & regions

stack sets are containers in a admin account

container stack instances .. which reference stacks

stack instance & stacks are in ‘target accounts’

each stack = 1 region in 1 account

Retain stack

allows you to remove stack instances from stack sets and by default it will remove the stacks in target accounts but can be set to retain Stack after removal.

Stack Failure Tolerance

the amount of individual deployment can fail before the Stack set is consider failed

Stack set operation options : Maximum concurrent accounts

how many stacks you want deployed in each region

When would you use CloudFormation StackSets

Enabling AWS config

Aws config Rules - MFA, EIPS,EBS encryption

create IAM Roles for cross-account access

CloudFormation DeletionPolicy

if you delete logical resource's from a template the physical resources is also deleted which could cause data loss. With deletion policy, you can define on each resource Delete(Default), Retain or (if supported) Snapshot.

What resources can an CloudFormation DeletionPolicy be used on ?

EBS volume, ElastiCache , Neptune ,RDS , Redshift

CF Stack Roles

CFN uses the permissions of the logged in identity which means you need permission for AWS CFN can assume a role to gain permissions This lets you implement role separation The identities creating the stack.. doesn't need resource permission-only PassRole

CloudFormation cfn-init

Another way you can provide configuration information to an ec2 instance simple configuration management system AWS::CloudFormation::Init part of logical resouces Desired state -What(Cfn-init decides How) Cfn-init helper-script -installed on EC2 OS(makes it so)

CloudFormation cfn-hup

if CloudFormation::Init is updated, it isn't run cfn-hup helper is a daemon which can be installed detects changes in resources metadata running configurable actions when a change is detected Update Stack → update config on EC2 instances

CloudFormation Change Sets

changes to stacks could cause no interruptions, some interruption, or Replacement which cause interruptions. change sets let you preview changes(A change set: over view of changes to a stack) multiple different version(lots of change sets) chosen changes can be applied by executing the change set

CloudFormation Custom Resources

Custom resources Lets CFN integrated with anything it doesn't yet or doesn't natively support passes data to something and gets data back from something CFN sends data to an endpoint that you define within the custom Resources that data gets sent to a lambada function or an SNS topic once created it then signals back to CFN

How does Cloud Formation work ? Explain the process ?

The **logical** resource defines the WHAT, and leaves the HOW up to the CFN product. A CFN stack creates a **physical** resource for every logical resource - updating or deleting them as a template changes.

What some defaults that parameters can be configured with ?

can be configured with **Defaults**, **AllowedValues**, **Min** and **Max** length & **Allowed Patterns**, **No Echo** & **Type**

How can parameters influence the resources created ?

can be referenced from within Logical resources which allows them influence physical resources and /or configuration