EC2

Question 1

What are the two default IP’s assigned to an EC2 instance when it is stood up in (assuming a route to internet)

Answer 1

Public (www)

Private (AWS network)

Question 2

How many IAM roles can be attached to an EC2 instance at once?

Answer 2

One

Question 3

Are ENI’s global?

Answer 3

No, they are bound to an AZ

Question 4

What is the role of the Ec2 spot advisor?

Answer 4

Spot advisor can provide configuration profiles which can either be directly applied to the spot fleet or customised and then applied to the fleet.

Question 5

Are you charged for an elastic IP associated against a
-Running
-Non Running
EC2 instance?

Answer 5

You are charged when you have an EIP associated with a non running instance.

Question 6

Can you detach an instances primary ENI?

Answer 6

No

Question 7

How many elastic IP’s can you have per account in AWS?

Answer 7

5 - but you can request more.

Question 8

When connecting to an Ec2 instance - you receive a connection time out. Why is this and what is the fix?

Answer 8

Port 22 is not open on the instances security group. You will need to open the port by creating an inbound rule on the instances security group.

Question 9

What placement group allows for the highest availability and what are the limits of that group?

Answer 9

Spread. All instances are on different hardware. Limits are that you can only have 7 instances per group. Use for critical apps where each instance needs to be isolated from other instances.

Question 10

You are ssh’ing into an ec2 instance using a pem file. You get an error stating the key file has bad permissions. What do you need to do?

Answer 10

You need to change the permissions of the key file using chmod 0400

Question 11

If I have an instance with 3 ENI’s , how many private IP addresses will I have on that instance?

Answer 11

3. 1 per ENI.

Question 12

Does an ENI need to be attached to an instance?

Answer 12

No. ENI’s can be created separately to an instance.

Question 13

How could you use an elastic IP to mask an instance failure?

Answer 13

You would remap the EIP from the failed instance to a working component. Its a hack, and the architecturally robust method is to use a load balancer and health checks.

Question 14

If a spot instance is killed by by AWS in your first billing hour, how much do you pay?

Answer 14

Nothing if AWS kills the instance rather than you.

Question 15

When is an EC2 UserData bootstrap script run?

Answer 15

On FIRST boot of the ec2 instance. Its is run once and only once

Question 16

Under which account are EC2 userdata bootscripts run?

Answer 16

root.

Question 17

Over what time period can you reserve a dedicated HOST for? Why would you use one?

Answer 17

3 years. Typically you would use one when you need to either control instance placement or need visibility of sockets and cores (usually bring your own licensing models). Also used if you have strong regulatory needs.

Question 18

What happens to an instances public IP when the instance is restarted? What happens to the private IP?

Answer 18

The public IP will most likely change. The private IP is stable though and won’t.

Question 19

How many instances at a time can an elastic IP be attached to?

Answer 19

One

Question 20

I have an ENI with a private IP if 23.345.102.16. If I attach this to an instance, what will the private IP be for that instance?

Answer 20

23.345.102.16 - the same. Attributes of an ENI follow it as its attached or detached.

Question 21

When you launch an instance, what are the tenancy options you can choose from?

Answer 21

Dedicated Instance
Dedicated Host
Share host

Question 22

What happens to the attributes of an ENI if it is detached from one instance and attached to a new instance?

Answer 22

The attributes of a network interface follow it as it’s attached or detached from an instance and reattached to another instance. When you move a network interface from one instance to another, network traffic is redirected to the new instance.

Question 23

what is eth0 with respect to a linux EC2 instance

Answer 23

Its your primary virtual network interface

Question 24

What is an EC2 Userdata bootstrap script used for?

Answer 24

Automating boot tasks on an EC2 Instance on instance first start - updates, software installs etc. The more tasks are in the boot script, the longer it will take for the instance to start

Question 25

If we have a web application which has a reasonably steady baseline workload throughout the year, but with some peaks, what combination of EC2 instances could you use?

Answer 25

You could provision reserved instances for the baseline periods, and then scale out using either spot or on demand instances to process the peaks.

Question 26

For a reserved instance, there are 3 types of payment options. What are they? (Hint: Not convertible)

Answer 26

No upfront
Partial Upfront
All Upfront

Question 27

Assume you are running a linux Ec2 on demand instance for 45 seconds - how long are you billed for? What if its running for 93 seconds?

Answer 27

You are billed per second on linux - with a minimum period of 60 seconds. In the first case you will be billed for 60 seconds. In the second, you will be billed for 93 seconds

Question 28

For a Dedicated instance - will instances from other customers run on the instance?

Answer 28

No. Other customers instances will not run on a dedicated instance - but your instances will.

Question 29

Do you pay for T2 micro instance usage in the first 12 months of your AWS account?

Answer 29

No, T2 micro usage is free tier within the first 12 months