AWS EC2 Interview Questions

Introduction

Amazon EC2 (Elastic Compute Cloud) expertise is becoming a prized asset. In this comprehensive guide, we've curated a collection of crucial interview questions encompassing EC2's nuances, functionalities, and best practices. Whether you're an aspiring cloud professional or a seasoned expert aiming to refine your skills, this resource will empower you with the knowledge to confidently navigate EC2-focused interviews and excel in the dynamic realm of cloud technology.

Q1). What Does Amazon EBS Offer for Amazon EC2 Instances, and How Does it Cater to Storage Needs?

Ans: Amazon EBS serves as persistent block storage for EC2 instances, functioning akin to a hard drive. Offering read/write access at a block level, it supports formatting with a file system. Each EBS volume can be attached to a single instance, ideal for installing operating systems and applications, and for persistent data storage. Users can provision specific sizes for storage volumes, choose from various volume types with different performance options, and conveniently increase volume sizes even while in use.

Q2). What is The Purpose of Instance Store Volumes in Certain Amazon EC2 Instance Types, and How Does their Local Nature Impact Data Persistence?

Ans: Certain Amazon EC2 instances support instance store volumes, offering high-performance storage for caches or temporary files. This storage, physically attached to the host machine, ensures efficient read/write operations. However, it's essential to note that data persists only while the instance is running on that host machine. Although the data survives instance reboots, AWS delete instance store data when you stop or terminate the instance.

Q3). How Does Networking Function for Amazon EC2 Instances Through Elastic Network Interfaces, and What Key Elements are Involved in Their Configuration?

Ans: Elastic network interfaces, serving as virtual network interfaces, facilitate networking for Amazon EC2 instances within the Amazon VPC. Each EC2 instance is assigned a primary network interface linked to a VPC subnet. The default configuration assigns instances to subnets within the default VPC, providing both private and public IP addresses for internal and internet communication. A security group acts as a stateful firewall, necessitating the definition of rules to allow network connections to the instance.

Q4). How Does Remote Access work for Linux and Windows Amazon EC2 Instances, and What are The Key Steps for Initial Sign-in and User Management?

Ans: By default, Linux EC2 instances use SSH, while Windows instances use RDP for remote access. Inbound rules on the instance's security group must allow access to these services. When launching an instance, a default administrator is provided based on the operating system and AMI. To sign in initially, an Amazon EC2 key pair must be specified. Once signed in, users can be created using relevant Linux or Windows tools

Q5). Who are The Default Users for Amazon Linux and Other Linux Operating Systems, As Well As for Windows Instances, and How Might the Default User Names Vary?

Ans: The default user for Amazon Linux is ec2-user, but for other Linux systems, it varies based on the AMI provider; for instance, Ubuntu Linux uses ubuntu. In Windows instances, the default user is Administrator, with the account name potentially differing based on the server's language; for example, in French, it becomes Administrateur.

Q6). What Constitutes an Amazon EC2 Key Pair, and How Does it Play a Role in Securing Sign-in Credentials for Both Linux and Windows Instances?

Ans: An Amazon EC2 key pair consists of a name, a public key, and a private key. AWS retains the public key, while it's the user's responsibility to securely store the private key. When specified during instance launch, the key pair secures sign-in credentials. For Linux instances, the public key is added to the ~/.ssh/authorized_keys file, and for Windows instances, the administrator account's password is encrypted with the public key, decryptable with the private key.

Q7). What are The Primary States of an Amazon EC2 Instance, and How Do Charges for Compute Resources and Persistent Storage Differ Based on these States?

Ans: An EC2 instance has three main states: running, stopped, and terminated, with intermediate states of pending, stopping, and shutting down. Compute resource charges apply only when an instance is running. However, EBS volumes persist data even when an instance is stopped, leading to charges for persistent storage independent of the instance's state. Upon launch, an instance moves from pending to running on a host machine.

Q8). What is an Alternative Method to Customize Software on Amazon EC2 Instances Without Direct Login, and How is User Data Utilized in This Process?

Ans: Beyond interactive sessions, customizing software on EC2 instances can be automated by providing user data during instance launch. For Linux, user data can be a shell script or cloud-init directive, while Windows instances use EC2Config or EC2Launch. By default, user data commands execute only during the instance's first boot. An example involves installing an Apache web server on an Amazon Linux 2 instance using a shell script as user data.

Q9). How Can IAM Roles Be Assigned to Amazon EC2 Instances, and What is The Role of Instance Profiles in This Process?

Ans: IAM roles can be assigned to EC2 instances, with the AWS SDK and CLI automatically discovering credentials through the EC2 metadata service. This eliminates the need for explicit credential configuration during bootstrapping. IAM roles are assigned indirectly through instance profiles, acting as containers for roles. An instance profile can be associated with multiple instances, but each instance can have only one profile and one IAM role. Instances can be associated or disassociated with an instance profile at launch or even while running.

Q10). How Does Communication Work Among Multiple Amazon EC2 Instances Within an Amazon VPC?

Ans: While the default Amazon VPC facilitates quick EC2 instance deployment, it's vital to grasp how multiple instances communicate within the VPC network. The AWS Certified Developer – Associate exam may assess this knowledge through troubleshooting questions. This section delves into Amazon VPC, empowering users to construct software-defined networks within an AWS Region.

Q11). How Does Amazon Virtual Private Cloud (Amazon VPC) Offer Network Isolation, and What Control Does a User Have Over The Connectivity of a VPC Within an AWS Region?

Ans: Amazon VPC provides logically isolated networks in an AWS account, spanning all Availability Zones in a specific Region. Users have full control over whether the VPC is connected to the internet, a private on-premises network, or other Amazon VPCs. Until explicit connections are created, instances within a VPC can communicate only with other instances in the same VPC.

Q12). What Defines Private IP Addresses in Amazon VPC?

Ans: Private IP addresses in Amazon VPC are IPv4 addresses inaccessible from the internet. Unique within a VPC, they serve for internal VPC traffic, private communication with corporate networks, and interactions with other VPCs.

Q13). Under what Conditions is a Public IP Address Automatically Assigned to an EC2 Instance?

Ans:The automatic assignment of a public IP address to an EC2 instance, alongside the private IP address, depends on the launch configuration and subnet options. Unlike the private IP address, the public IP is reachable from the internet. AWS manages the association between an instance and its public IPv4 address, which persists only while the instance is running. Manual association or disassociation of public IP addresses from an instance is not possible.

Q14). How does an Elastic IP Address Differ from a Public IP Address, and What Control Do Users have Over the Association of Elastic IP Addresses?

Ans: An Elastic IP address, akin to a public IP, is an IPv4 address reachable from the internet. Unlike public IP addresses, users manage the association between instances and Elastic IP addresses. Users have control over the allocation, association, disassociation, and movement of these addresses between instances. Additionally, Elastic IP addresses can be assigned to infrastructure like NAT gateways, sourced either from AWS-managed IP pools or blocks of IPv4 addresses brought to the AWS account.

Q15). What is The Role of Subnets Within an Amazon VPC, How are They Associated with Availability Zones, and How are Private IP Addresses Defined for Subnets?

Ans: In an Amazon VPC, subnets are defined within specific Availability Zones and have their own block of private IP addresses using CIDR notation. Each subnet's IP address range is a subset of the overall VPC range, ensuring no overlap with other subnets. For instance, a subnet with CIDR block 10.0.0.0/24 includes addresses from 10.0.0.0 to 10.0.0.255. Amazon VPC reserves the first four and last IP addresses, leaving 251 usable addresses within the subnet.

Q16). How Do Security Groups Function as a Firewall for Amazon EC2 Instances, and What Aspects of Network Traffic Can Be Controlled Through Security Group Rules?

Ans: Security groups serve as stateful firewalls for EC2 instances, allowing specification of source or destination, protocols, and ports in defined rules. Any changes to security group rules propagate to associated instances. Inbound security group rules provide control over the source, protocols, and ports of permitted network traffic. For instance, one could enable TCP connections originating from the IPv4 address of a home network, facilitating SSH administration of an EC2 instance.

Q17). How do Network Access Control Lists (network ACLs) Complement Routes in Controlling Traffic Within a Subnet?

Ans: Similar to routes, network ACLs enable administrators to manage incoming and outgoing subnet traffic. Comprising both inbound and outbound rules, network ACLs can be associated with multiple subnets in a particular Amazon VPC, serving as a stateless firewall for subnet-specific traffic. While security group rules only allow traffic, network ACL rules provide the additional capability to permit specific types of traffic and deny specific traffic.

Q18). How does Network Address Tanslation (NAT) Facilitate Outbound Internet Requests for Instances in Private Subnets?

Ans: Network address translation (NAT) enables instances in private subnets to make outbound internet requests while preventing inbound connections. This can be achieved through an Amazon EC2 instance configured for NAT or a NAT gateway. Instances in private subnets retain their private IP addresses and share the public IP address of the NAT when making internet requests, ensuring security from inbound internet connections.

Conclusion

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