AWS Certification Preparation: AWS Ec2 Facts, Faqs and Summaries, Top 10 Questions and Answers Dump




AWS Ec2 Facts and summaries, AWS Ec2 Top 10 Questions and Answers Dump

Definition 1: Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides secure, resizable compute capacity in the cloud. It is designed to make web-scale cloud computing easier for developers.

Definition 2: Amazon Elastic Compute Cloud (EC2) forms a central part of Amazon.com’s cloud-computing platform, Amazon Web Services (AWS), by allowing users to rent virtual computers on which to run their own computer applications.




AWS Ec2 Facts and summaries

  1. Can users SSH to EC2 instances using their AWS user name and password?
    No. User security credentials created with IAM are not supported for direct authentication to customer EC2 instances. Managing EC2 SSH credentials is the customer’s responsibility within the EC2 console.
  2. Amazon Elastic Compute Cloud (Amazon EC2) is a web service that provides resizable compute capacity in the cloud. It is designed to make web-scale computing easier for developers.

  3. What is the difference between using the local instance store and Amazon Elastic Block Store (Amazon EBS) for the root device?
    When you launch your Amazon EC2 instances you have the ability to store your root device data on Amazon EBS or the local instance store. By using Amazon EBS, data on the root device will persist independently from the lifetime of the instance. This enables you to stop and restart the instance at a subsequent time, which is similar to shutting down your laptop and restarting it when you need it again.
    Alternatively, the local instance store only persists during the life of the instance. This is an inexpensive way to launch instances where data is not stored to the root device. For example, some customers use this option to run large web sites where each instance is a clone to handle web traffic.

  4. How many instances can I run in Amazon EC2?
    You are limited to running up to a total of 20 On-Demand instances across the instance family, purchasing 20 Reserved Instances, and requesting Spot Instances per your dynamic Spot limit per region.

  5. How quickly can I scale my capacity both up and down?
    Amazon EC2 provides a truly elastic computing environment. Amazon EC2 enables you to increase or decrease capacity within minutes, not hours or days. You can commission one, hundreds or even thousands of server instances simultaneously. When you need more instances, you simply call RunInstances, and Amazon EC2 will typically set up your new instances in a matter of minutes. Of course, because this is all controlled with web service APIs, your application can automatically scale itself up and down depending on its needs.
  6. When dealing with session state in EC2-based applications using Elastic load balancers which option is generally thought of as the best practice for managing user sessions?
    Having the ELB distribute traffic to all EC2 instances and then having the instance check a caching solution like ElastiCache running Redis or Memcached for session information
  7. What is one key difference between an Amazon EBS-backed and an instance-store backed instance?
    Amazon EBS-backed instances can be stopped and restarted without losing data
  8. How is the AWS Ec2 service different than a plain hosting service?
    Traditional hosting services generally provide a pre-configured resource for a fixed amount of time and at a predetermined cost. Amazon EC2 differs fundamentally in the flexibility, control and significant cost savings it offers developers, allowing them to treat Amazon EC2 as their own personal data center with the benefit of Amazon.com’s robust infrastructure.
    When computing requirements unexpectedly change (up or down), Amazon EC2 can instantly respond, meaning that developers have the ability to control how many resources are in use at any given point in time. In contrast, traditional hosting services generally provide a fixed number of resources for a fixed amount of time, meaning that users have a limited ability to easily respond when their usage is rapidly changing, unpredictable, or is known to experience large peaks at various intervals.
    Secondly, many hosting services don’t provide full control over the compute resources being provided. Using Amazon EC2, developers can choose not only to initiate or shut down instances at any time, they can completely customize the configuration of their instances to suit their needs – and change it at any time. Most hosting services cater more towards groups of users with similar system requirements, and so offer limited ability to change these.
    Finally, with Amazon EC2 developers enjoy the benefit of paying only for their actual resource consumption – and at very low rates. Most hosting services require users to pay a fixed, up-front fee irrespective of their actual computing power used, and so users risk overbuying resources to compensate for the inability to quickly scale up resources within a short time frame.

  9. What load balancing options does the Elastic Load Balancing service offer?
    Elastic Load Balancing offers two types of load balancers that both feature high availability, automatic scaling, and robust security. These include the Classic Load Balancer that routes traffic based on either application or network level information, and the Application Load Balancer that routes traffic based on advanced application level information that includes the content of the request.

  10. When should I use the Classic Load Balancer and when should I use the Application Load Balancer?
    The Classic Load Balancer is ideal for simple load balancing of traffic across multiple EC2 instances, while the Application Load Balancer is ideal for applications needing advanced routing capabilities, microservices, and container-based architectures. Please visit Elastic Load Balancing for more information.

  11. Can I get a history of all EC2 API calls made on my account for security analysis and operational troubleshooting purposes?
    Yes. To receive a history of all EC2 API calls (including VPC and EBS) made on your account, you simply turn on CloudTrail in the AWS Management Console. For more information, visit the CloudTrail home page.

  12. How to get information about Ec2 instance type?
    AWS EC2 Instance info
  13. Can I access the metrics data for a terminated Amazon EC2 instance or a deleted Elastic Load Balancer?
    Yes. Amazon CloudWatch stores metrics for terminated Amazon EC2 instances or deleted Elastic Load Balancers for 2 weeks.

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Reference: AWS Ec2 Faqs




AWS Ec2 Top 10 Questions and Answers Dump

Q0:
When dealing with session state in EC2-based applications using Elastic load balancers which option is generally thought of as the best practice for managing user sessions?

  • A. Having the ELB distribute traffic to all EC2 instances and then having the instance check a caching solution like ElastiCache running Redis or Memcached for session information
  • B. Permanently assigning users to specific instances and always routing their traffic to those instances
  • C. Using Application-generated cookies to tie a user session to a particular instance for the cookie duration
  • D. Using Elastic Load Balancer generated cookies to tie a user session to a particular instance

A.
Amazon ElastiCache for Memcached is a Memcached-compatible in-memory key-value store service that can be used as a cache or a data store. It delivers the performance, ease-of-use, and simplicity of Memcached. ElastiCache for Memcached is fully managed, scalable, and secure – making it an ideal candidate for use cases where frequently accessed data must be in-memory. It is a popular choice for use cases such as Web, Mobile Apps, Gaming, Ad-Tech, and E-Commerce.

Reference: Memcached

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Q2: You are attempting to SSH into an EC2 instance that is located in a public subnet. However, you are currently receiving a timeout error trying to connect. What could be a possible cause of this connection issue?

  • A. The security group associated with the EC2 instance has an inbound rule that allows SSH traffic, but does not have an outbound rule that allows SSH traffic.
  • B. The security group associated with the EC2 instance has an inbound rule that allows SSH traffic AND has an outbound rule that explicitly denies SSH traffic.
  • C. The security group associated with the EC2 instance has an inbound rule that allows SSH traffic AND the associated NACL has both an inbound and outbound rule that allows SSH traffic.
  • D. The security group associated with the EC2 instance does not have an inbound rule that allows SSH traffic AND the associated NACL does not have an outbound rule that allows SSH traffic.

D. Security groups are stateful, so you do NOT have to have an explicit outbound rule for return requests. However, NACLs are stateless so you MUST have an explicit outbound rule configured for return request.

Reference: Comparison of Security Groups and Network ACLs

AWS Security Groups and NACL

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Q3: Which API call would best be used to describe an Amazon Machine Image?

  • A. ami-describe-image
  • B. ami-describe-images
  • C. DescribeImage
  • D. DescribeImages

D. In general, API actions stick to the PascalCase style with the first letter of every word capitalized.

Reference: API DescribeImages

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Q4: What is one key difference between an Amazon EBS-backed and an instance-store backed instance?

  • A. Autoscaling requires using Amazon EBS-backed instances
  • B. Virtual Private Cloud requires EBS backed instances
  • C. Amazon EBS-backed instances can be stopped and restarted without losing data
  • D. Instance-store backed instances can be stopped and restarted without losing data

C. Instance-store backed images use “ephemeral” storage (temporary). The storage is only available during the life of an instance. Rebooting an instance will allow ephemeral data stay persistent. However, stopping and starting an instance will remove all ephemeral storage.

Reference: What is the difference between EBS and Instance Store?

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Q15: After having created a new Linux instance on Amazon EC2, and downloaded the .pem file (called Toto.pem) you try and SSH into your IP address (54.1.132.33) using the following command.
ssh -i my_key.pem ec2-user@52.2.222.22
However you receive the following error.
@@@@@@@@ WARNING: UNPROTECTED PRIVATE KEY FILE! @ @@@@@@@@@@@@@@@@@@@
What is the most probable reason for this and how can you fix it?

  • A. You do not have root access on your terminal and need to use the sudo option for this to work.
  • B. You do not have enough permissions to perform the operation.
  • C. Your key file is encrypted. You need to use the -u option for unencrypted not the -i option.
  • D. Your key file must not be publicly viewable for SSH to work. You need to modify your .pem file to limit permissions.

D. You need to run something like: chmod 400 my_key.pem

Reference:

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Q5: You have an EBS root device on /dev/sda1 on one of your EC2 instances. You are having trouble with this particular instance and you need to either Stop/Start, Reboot or Terminate the instance but you do NOT want to lose any data that you have stored on /dev/sda1. However, you are unsure if changing the instance state in any of the aforementioned ways will cause you to lose data stored on the EBS volume. Which of the below statements best describes the effect each change of instance state would have on the data you have stored on /dev/sda1?

  • A. Whether you stop/start, reboot or terminate the instance it does not matter because data on an EBS volume is not ephemeral and the data will not be lost regardless of what method is used.
  • B. If you stop/start the instance the data will not be lost. However if you either terminate or reboot the instance the data will be lost.
  • C. Whether you stop/start, reboot or terminate the instance it does not matter because data on an EBS volume is ephemeral and it will be lost no matter what method is used.
  • D. The data will be lost if you terminate the instance, however the data will remain on /dev/sda1 if you reboot or stop/start the instance because data on an EBS volume is not ephemeral.

D. The question states that an EBS-backed root device is mounted at /dev/sda1, and EBS volumes maintain information regardless of the instance state. If it was instance store, this would be a different answer.

Reference: AWS Root Device Storage

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Q6: EC2 instances are launched from Amazon Machine Images (AMIs). A given public AMI:

  • A. Can only be used to launch EC2 instances in the same AWS availability zone as the AMI is stored
  • B. Can only be used to launch EC2 instances in the same country as the AMI is stored
  • C. Can only be used to launch EC2 instances in the same AWS region as the AMI is stored
  • D. Can be used to launch EC2 instances in any AWS region

C. AMIs are only available in the region they are created. Even in the case of the AWS-provided AMIs, AWS has actually copied the AMIs for you to different regions. You cannot access an AMI from one region in another region. However, you can copy an AMI from one region to another

Reference: https://aws.amazon.com/amazon-linux-ami/

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Q7: Which of the following statements is true about the Elastic File System (EFS)?

  • A. EFS can scale out to meet capacity requirements and scale back down when no longer needed
  • B. EFS can be used by multiple EC2 instances simultaneously
  • C. EFS cannot be used by an instance using EBS
  • D. EFS can be configured on an instance before launch just like an IAM role or EBS volumes

A. and B.

Reference: https://aws.amazon.com/efs/

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Q8: You are in charge of deploying an application that will be hosted on an EC2 Instance and sit behind an Elastic Load balancer. You have been requested to monitor the incoming connections to the Elastic Load Balancer. Which of the below options can suffice this requirement?

  • A. Use AWS CloudTrail with your load balancer
  • B. Enable access logs on the load balancer
  • C. Use a CloudWatch Logs Agent
  • D. Create a custom metric CloudWatch lter on your load balancer

Answer – B
Elastic Load Balancing provides access logs that capture detailed information about requests sent to your load balancer. Each log contains information such as the time the request was received, the client’s IP address, latencies, request paths, and server responses. You can use these access logs to analyze traffic patterns and troubleshoot issues.
Reference: Access Logs for Your Application Load Balancer

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Q9: When deploying application code to EC2, the AppSpec file can be written in which language?

  • A. JSON
  • B. JSON or YAML
  • C. XML
  • D. YAML

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Q9:

  • A.
  • B.
  • C.
  • D.

Reference:

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Q10:

  • A.
  • B.
  • C.
  • D.

Reference:

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