A complete guide to prepare for AWS interviews with EC2, Security Groups, EBS, DLM, Snapshots, Load Balancers, and Auto Scaling.
EC2 Instances
Q1. What is an EC2 instance?
An EC2 instance is a virtual server in the Amazon Elastic Compute Cloud (EC2) service. It provides scalable computing capacity in the AWS cloud, allowing users to run applications and services.
Q2. Can you explain the difference between an instance and an AMI?
An instance is a running virtual server in EC2, while an AMI (Amazon Machine Image) is a pre-configured virtual machine template that serves as a blueprint for launching instances. You use an AMI to create, launch, and clone instances.
Q3. How do you launch an EC2 instance?
You can launch an EC2 instance through the AWS Management Console, AWS CLI (Command Line Interface), or SDKs using the "RunInstances" command.
Q4. What is the significance of an instance type?
An instance type defines the hardware of the host computer used for your instance. Each instance type offers different combinations of CPU, memory, storage, and networking capacity. It determines the performance and pricing of your instance.
Q5. What is the purpose of user data in EC2 instances?
User data allows you to run scripts or provide configuration information when launching an instance. This is useful for tasks like installing software, setting up configurations, or running custom startup scripts.
Q6. How can you stop and start an EC2 instance?
You can stop an EC2 instance through the AWS Management Console, AWS CLI, or SDKs. To start a stopped instance, use the same methods.
Q7. What is the difference between stopping and terminating an EC2 instance?
When you stop an instance, it is turned off but remains in the AWS infrastructure. You can start it again later. Terminating an instance permanently deletes it and its associated resources.
Q8. How do you resize an EC2 instance?
You can resize an EC2 instance by stopping it, changing its instance type in the AWS Management Console, and then starting it again.
Q9. Can you attach an IAM role to an existing EC2 instance?
Yes, you can associate an IAM role with an existing EC2 instance. You do this by stopping the instance, modifying the instance settings, and attaching the desired IAM role.
Q10. Explain the concept of an Elastic IP address in EC2.
An Elastic IP (EIP) is a static public IPv4 address that you own within your AWS account. Unlike a regular public IP (which changes if you stop or restart your EC2 instance), an Elastic IP stays the same. You can assign or reassign it to different EC2 instances, which makes it useful for maintaining a consistent public endpoint.
Security Groups
Q11. What is a security group in EC2?
A security group acts as a virtual firewall for an instance. It controls inbound and outbound traffic, allowing or denying communication based on rules defined for the group.
Q12. How is a security group different from a Network Access Control List (NACL)?
A security group operates at the instance level, while a Network Access Control List (NACL) operates at the subnet level. Security groups are stateful, while NACLs are stateless.
Q13. Can you associate multiple security groups with a single EC2 instance?
Yes, you can associate multiple security groups with a single EC2 instance. The rules of all associated security groups are aggregated.
Q14. What are inbound and outbound rules in a security group?
Inbound rules control the incoming traffic to an instance, while outbound rules control the outgoing traffic. Each rule defines a combination of protocol, port, and source/destination for the traffic.
Q15. How does security group evaluation work?
Security group rules are evaluated based on the most specific rule that matches the traffic. If no rule explicitly allows the traffic, it is denied by default. The rule with the highest priority takes precedence.
EBS Volumes
Q16. What is an EBS volume?
An EBS (Elastic Block Store) volume is a block-level storage device that you can attach to an EC2 instance. It provides persistent storage that persists independently from the life of an instance.
Q17. What is the difference between EBS-backed and instance-store backed instances?
EBS-backed instance:
• The computer’s main disk is on Amazon EBS (cloud hard drive).
• Data stays safe even if the computer (instance) is turned off or restarted.
Instance-store backed instance:
• The computer’s main disk is built into the server itself.
• Data is lost if the computer (instance) is turned off or crashes.
Q18. How can you increase the size of an EBS volume?
You can increase the size of an EBS volume, but it requires creating a snapshot of the existing volume, then creating a larger volume from that snapshot, and finally attaching it to the instance.
Q19. Can you attach multiple EBS volumes to a single EC2 instance?
Yes, you can attach multiple EBS volumes to a single EC2 instance, each identified by a unique device name.
Q20. Explain the difference between General Purpose SSD (gp2) and Provisioned IOPS SSD (io1).
General Purpose SSD (gp2) provides balanced performance for a wide range of workloads. Provisioned IOPS SSD (io1) allows you to specify a consistent IOPS rate, making it ideal for I/O-intensive applications.
DLM (Data Lifecycle Manager)
Q21. What is AWS Data Lifecycle Manager (DLM)?
AWS Data Lifecycle Manager is a service that automates the creation, retention, and deletion of EBS snapshots. It helps in managing the lifecycle of your EBS volumes' backups.
Q22. How do you create a lifecycle policy for EBS snapshots?
You create a lifecycle policy in the AWS DLM console or by using the DLM API. The policy defines the rules for creating and retaining snapshots, such as the frequency and retention period.
Q23. Explain the concept of retention policies in DLM.
Retention policies in DLM specify how many snapshots to retain and for how long. You can set up policies to keep a certain number of snapshots, or to retain snapshots for a specific number of days.
Snapshots
Q24. What is an EBS snapshot?
An EBS snapshot is a point-in-time copy of an EBS volume. It captures the data and configuration of the volume, allowing you to restore it or create new volumes from the snapshot.
Q25. How do you create a snapshot of an EBS volume?
You can create a snapshot using the AWS Management Console, AWS CLI, or SDKs. You select the EBS volume, initiate the snapshot process, and it will be created asynchronously.
Q26. Can you create a snapshot of a root volume that is attached to a running EC2 instance?
Yes, you can create a snapshot of a root volume while it is attached to a running instance. However, it's recommended to stop the instance to ensure data consistency.
Q27. What is the difference between a snapshot and an AMI?
A snapshot is a point-in-time copy of an EBS volume, while an AMI (Amazon Machine Image) is a pre-configured image that can be used to launch EC2 instances. An AMI can include multiple snapshots.
Load Balancers
Q28. What is an Elastic Load Balancer (ELB)?
An Elastic Load Balancer (ELB) is a service that automatically distributes incoming application traffic across multiple targets, such as EC2 instances, containers, or IP addresses.
Q29. Can you explain the types of load balancers in AWS?
AWS offers three types of load balancers:
• Application Load Balancer (ALB) – operates at the application layer
• Network Load Balancer (NLB) – operates at the transport layer
• Classic Load Balancer – provides basic load balancing
Q30. How does an Application Load Balancer (ALB) differ from a Network Load Balancer (NLB)?
ALB operates at the application layer and can route traffic based on content. It's best suited for web applications.
NLB operates at the transport layer and is ideal for high-performance, low-latency use cases.
Q31. What is the purpose of a Target Group?
A Target Group is used with an AWS Load Balancer to decide where incoming traffic should go. It contains registered targets like EC2 instances, and the load balancer sends traffic to only the healthy targets using its load balancing rules.
Auto Scaling Group
Q32. What is Auto Scaling in AWS?
Auto Scaling is a feature that automatically adjusts the number and size of your EC2 instances based on the conditions you set. It helps maintain application availability and scale resources efficiently.
Q33. How do you set up an Auto Scaling group?
To set up an Auto Scaling group, you define a launch configuration or launch template that specifies the instance type, AMI, key pair, and security groups. Then, you create an Auto Scaling group using this configuration.
Q34. Explain the significance of Launch Configurations in Auto Scaling.
A Launch Configuration is a template that defines the parameters for launching instances in an Auto Scaling group. It includes information like the instance type, AMI, key pair, and security groups.
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