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- Okay, so now let's talk about

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the Instance Metadata Service.

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The Instance Metadata
Service is a very special

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URL available to us that we can query

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in order to get information
about an EC2 instance,

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and that URL looks something like this,

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HTTP 169.254.169.254/latest/meta-data,

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and, of course, if we
were to query that URL,

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we would get back a list of
other URLs that we can reach,

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and what this does is that
from within an EC2 instance,

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we can use this URL to retrieve

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information about that instance.

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An EC2 instance can use this

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to get information about itself.

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We cannot access this URL
from outside an instance,

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and we cannot use this URL
in order for one instance

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to get information about another.

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It's always so that one EC2 instance

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can get information about itself,

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and so this is very useful

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when it comes to
bootstrapping EC2 instances

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or doing some type of
programmatic response

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to the environment

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so that when a machine comes
to life, it can go and find out

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what type of machine is it supposed to be?

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What type of job is it
supposed to perform?

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What is my IP address?

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What type of volumes do I have attached?

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Those kinds of things are available,

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and so there's all kinds of information

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that we can retrieve through
the Instance Metadata Service.

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We can retrieve the machine image ID.

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We can retrieve the DNS
host name, the instance ID,

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the instance type, the private IP address,

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and of course, again, this is often used

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with different types of scripts

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for instance-specific configuration.

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So one of the really powerful
and beautiful things about AWS

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is the level of automation,

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and as we will talk more about later,

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the only way to truly
realize the power of AWS,

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the cost savings, the
flexibility, the agility,

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is through leveraging automation,

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and this is one of the
critical or key components

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to enabling automation,

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is when we have instances come
to life through autoscaling

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which we'll talk about later,

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ideally, that instance is
able to configure itself,

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ensure that whatever software is needed

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is installed, configured,

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and whatever processes
are needed are running

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so that machine can come
to life and get to work

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doing what it's supposed to do,

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and so the Instance Metadata Service

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provides a very rich API

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so that machine has all of the information

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that it could possibly
need at its disposal

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in order to programmatically,

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essentially become what
it's supposed to become

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and get to work doing
what it's supposed to do,

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and so we will take a closer look

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at the Instance Metadata
Service in upcoming lessons.