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Are you preparing for AWS EC2 interview? AWS EC2 is the amazon web services Elastic Compute Cloud which is the center for Amazon cloud platform. Customers can rent virtual computers using this so that they can use their own applications. As it is virtual, it eliminates the need to spend money on hardware. Applications can be easily developed and deployed. It provides secure, resizable compute capacity in the cloud. Data stored is persistent in the AWS EBS (Elastic Block Store). Many of the people are not aware of this job so there is huge demand for this technology in the market. Good knowledge on these concepts will fetch you the job. Wisdomjobs framed AWS EC2 interview questions and answers to make it easier for your interview preparation.
Amazon Elastic Compute Cloud (Amazon EC2) is a Amazon web service that provides resizable (scalable) computing capacity in the cloud. You can use Amazon EC2 to launch as many virtual servers you need. In Amazon EC2 you can configure security and networking as well as manage storage.Amazon EC2 service also helps in obtaining and configuring capacity using minimal friction.
As the Amazon EC2 service is a cloud service so it has all the cloud features.
Amazon EC2 provides the following features:
For secure Amazon EC2 best practices, follow the following steps:
Amazon EC2 provides many data storage options for your instances. Each option has a unique combination of performance and durability. These storages can be used independently or in combination to suit your requirements.
There are mainly four types of storages provided by AWS:
Stopping and Starting an instance: When an instance is stopped, the instance performs a normal shutdown and then transitions to a stopped state. All of its Amazon EBS volumes remain attached, and you can start the instance again at a later time. You are not charged for additional instance hours while the instance is in a stopped state.
Terminating an instance: When an instance is terminated, the instance performs a normal shutdown, then the attached Amazon EBS volumes are deleted unless the volume’s deleteOnTermination attribute is set to false. The instance itself is also deleted, and you can’t start the instance again at a later time.
As the Amazon EC2 service is a cloud facility so it has entirely all the cloud features. Amazon EC2 delivers the subsequent features:
Amazon EC2 offers numerous data storage choices for your occurrences. Each choice has an exclusive mixture of presentation and sturdiness. These storages can be used self-sufficiently or in grouping to suit your necessities.
There are chiefly four types of storages offered by AWS:
Yes, it can be cast-off for instances with root approaches backed by native occurrence storage. By using Amazon S3, developers have access to the similar extremely scalable, dependable, fast, low-priced data storage substructure that Amazon uses to track its own worldwide network of web sites. In order to perform systems in the Amazon EC2 atmosphere, developers use the tools providing to load their Amazon Machine Images (AMIs) into Amazon S3 and to transfer them between Amazon S3 and Amazon EC2. Additional use case might be for websites hosted on EC2 to load their stationary content from S3
Amazon EC2 is hosted in multiple locations world-wide. These locations are composed of regions and Availability Zones. Each region is a separate geographic area. Each region has multiple, isolated locations known as Availability Zones.
Each region is completely independent. Each Availability Zone is isolated, but the Availability Zones in a region are connected through low-latency links. The following diagram illustrates the relationship between regions and Availability Zones.
Each region is completely independent and each Availability Zone is isolated. When you view your resources, you’ll only see the resources tied to the region you have specified.
To launch a EC2 instance, you must select an AMI that’s in the same region (if the AMI is in another region then you can copy the AMI to the region you are using). Now select an Availability Zone or let AWS choose for you. After creating the EC2 instance, it will show up in selected Availability Zone.
When you launch an instance, the Root Device Volume contains the image used to boot the instance.
You can launch an instance from one of two types of AMIs:
By default, the root device volume for an AMI backed by Amazon EBS is deleted when the instance terminates. To change the default behavior, set the DeleteOnTermination attribute to false using a block device mapping.
Security groups act as a firewall for associated instances, controlling both inbound and outbound traffic at the instance level.
Following are the features of the Security Group in Amazon EC2:
We can create Security Group in Amazon EC2 using the Amazon EC2 console. To launch instances in multiple regions, we’ll need to create a Security Group in each region.
Following are the steps to create Security Group in Amazon EC2:
We can launch Linux/Windows Amazon EC2 instance using AWS Management Console.
Following are the steps to create Amazon EC2 instance:
There are several ways to connect to a Linux instance. One of the commonly used method is to connect Linux instance from Windows local machine using PuTTY.
Following are the steps to connect to a Linux instance:
We can attach an EBS volume to one of our instances that is in the same Availability Zone as the Volume.
Following are the steps to attache an EBS volumn to an instance using console:
After we are finished with the instance we created, we can clean up by terminating the instance.
Following are the steps to terminate the EC2 instance:
To get the maximum benefit from and satisfaction with Amazon EC2.
There are mainly four best practices:
Amazon Web Services provides several ways to access Amazon EC2, like web-based interface, AWS Command Line Interface (CLI) and Amazon Tools for Windows Powershell. First, you need to sign up for an AWS account and you can access Amazon EC2.
Amazon EC2 provides a Query API. These requests are HTTP or HTTPS requests that use the HTTP verbs GET or POST and a Query parameter named Action.
An Amazon Machine Image (AMI) is a template that contains a software configuration (for example, an operating system, an application server, and applications). From an AMI, we launch an instance, which is a copy of the AMI running as a virtual server in the cloud. We can even launch multiple instances of an AMI.
We can launch different types of instances from a single AMI. An instance type essentially determines the hardware of the (pivotal training) host computer used for your instance. Each instance type offers different compute and memory capabilities.
After we launch an instance, it looks like a traditional host, and we can interact with it as we would do with any computer. We have complete control of our instances; we can use sudo to run commands that require root privileges.
You can migrate your EC2 instance from one Availability Zone to another.
Following are the steps to migrate an Instance to another Availability Zone:
AWS uses public-key cryptography to secure the login information for your instance. A Linux instance has no password; you use a key pair to log in to your instance securely.
You specify the name of the key pair when you launch your instance, then provide the private key when you log in using SSH.
We can create one using the Amazon EC2 console. To launch instances in multiple regions, we’ll need to create a key pair in each region.
Following are the steps to create Key Pair:
Key pair is used to log in to your instance securely. This is public-key cryptography to secure the login information for your instance.
You can customize a instance that is launched from a public AMI and then save that configuration as a custom AMI for your own use.
Instances that you launch from your AMI use all the customizations that you’ve made.
We can determine the Root Device type of AMI using following 2 methods.
Method 1: Following are the steps to determine the Root Device type of an AMI using the console
Method 2: Following are the steps to determine the root device type of an AMI using the command line
We can use one of the following commands.
All AMIs are categorized as either backed by Amazon EBS or backed by instance store.
Backed by Amazon EBS – means that the root device for an instance launched from the AMI is an Amazon EBS volume created from an Amazon EBS snapshot.
Backed by instance store – means that the root device for an instance launched from the AMI is an instance store volume created from a template stored in Amazon S3.
Root device size limit for –
Amazon EBS – Backed is 16 TiB
Amazon Instance Store-Backed is 10 GiB
For example: if hourly instance charge for your instance is $0.10 and if you were to run that instance for one hour without stopping it, you would be charged $0.10. If you stopped and restarted that instance twice during that hour, then you would be charged $0.30 for that hour of usage (the initial $0.10, plus 2 x $0.10 for each restart).
A shared AMI is an AMI that a developer created and made available for other developers to use.
One of the easiest ways to get started with Amazon EC2 is to use a shared AMI that has the components you need and then add custom content. You can also create your own AMIs and share them with others.
AWS recommends that your AMIs download and upgrade the Amazon
EC2 AMI creation tools during startup. This ensures that new AMIs based on your shared AMIs have the latest AMI tools.
For Amazon Linux, add the following to /etc/rc.local:
# Update the Amazon EC2 AMI tools
echo ” + Updating EC2 AMI tools”
yum update -y aws-amitools-ec2
echo ” + Updated EC2 AMI tools”
Using a fixed root password for a public AMI is a security risk that can quickly become known. Even relying on users to change the password after the first login opens a small window of opportunity for potential abuse.
Following are the steps to disable password-based remote logins for the root user:
Open the /etc/ssh/sshd_config file with a text editor and locate the following line:
Change the line to:
The location of this configuration file might differ for your distribution.
Amazon EC2 uses public–key cryptography to encrypt and decrypt login information. Public–key cryptography uses a public key to encrypt a piece of data, such as a password, then the recipient uses the private key to decrypt the data. The public and private keys are known as a key pair.
After configuring the AMI to prevent logging in using a password, you must make sure users can log in using another mechanism.
Starting, stopping and terminating are the three states in an EC2 instance, let’s discuss them in detail:
First of all, let’s understand that Spot Instance, On-Demand instance and Reserved Instances are all models for pricing. Moving along, spot instances provide the ability for customers to purchase compute capacity with no upfront commitment, at hourly rates usually lower than the On-Demand rate in each region. Spot instances are just like bidding, the bidding price is called Spot Price.
The Spot Price fluctuates based on supply and demand for instances, but customers will never pay more than the maximum price they have specified. If the Spot Price moves higher than a customer’s maximum price, the customer’s EC2 instance will be shut down automatically.
But the reverse is not true, if the Spot prices come down again, your EC2 instance will not be launched automatically, one has to do that manually. In Spot and On demand instance, there is no commitment for the duration from the user side, however in reserved instances one has to stick to the time period that he has chosen.
The primary private IP address cannot be changed. Secondary private addresses can be unassigned, assigned or moved between interfaces or instances at any point.
Yes, it can be used for instances with root devices backed by local instance storage. By using Amazon S3, developers have access to the same highly scalable, reliable, fast, inexpensive data storage infrastructure that Amazon uses to run its own global network of web sites. In order to execute systems in the Amazon EC2 environment, developers use the tools provided to load their Amazon Machine Images (AMIs) into Amazon S3 and to move them between Amazon S3 and Amazon EC2.
Another use case could be for websites hosted on EC2 to load their static content from S3.
The best way of connecting to your cloud resources (for ex- ec2 instances) from your own data center (for eg- private cloud) is a VPC. Once you connect your datacenter to the VPC in which your instances are present, each instance is assigned a private IP address which can be accessed from your datacenter. Hence, you can access your public cloud resources, as if they were on your own network.
Rebooting an instance is like rebooting a PC. The hard disk isn’t affected. You don’t return to the image’s original state, but the contents of the hard disks are those before the reboot.
Rebooting isn’t associated with billing. Billing starts when you instantiate an image and stops when you terminate it. Rebooting in between hasn’t any effect.
In Amazon EC2, we can even bid for getting a computing instance. Any instance procured by bidding is a Spot Instance. Multiple users bid for an EC2 Instance. Once the bid price exceeds the Spot price, the user with the highest bid gets it. As long as their bid price remains higher than the Spot price, they can keep using it.
Spot price varies with the supply and demand. Once Spot price exceeds Bid price, the instance will be taken back from the user.
“On-Demand” instances allow the user to use the compute by hour without requiring long term commitment. There are no guarantees that the user will always be able to launch specific instance types in an availability zone, though AWS tries it’s best to meet the needs. This service is preferable for POCs and they do not suffer an interruption of the service(by AWS) like Spot instances.
“Spot” instances are a bid_for_low_price version of On-Demand instances, but could be shut down by AWS anytime the Spot instance price goes higher than bid price. Spot price fluctuates based on the supply and demand of the capacity. It’s essentially the leftover capacity of AWS to be used. There is no difference in the performance compared to On-Demand instances and is usually cheaper than On-demand instances as there is no guarantee provided over the availability. The user can choose a start time and end time for the instances or can make a persistent request(no end time specified) for this service. This service is preferable for computing needs which are not tied to any deadlines, computing needs are large and the interruption of service is acceptable.
Some of the main features of Classic Load Balancer (CLB) in Amazon EC2 are as follows:
Health Check: Based on the result of Health Check, Classic Load Balancer can decide to route the traffic. If any instance has unhealthy results, CLB will not route the traffic to that instance.
Security: We can create security groups for CLB in Virtual Private Cloud (VPC). With these features, it is easy to implement secure load balancing within a network.
High Availability: With CLB, we can distribute traffic among EC2 instances in single or multiple Availability Zones. This helps in providing very high scale of availability for the incoming traffic.
Sticky Sessions: CLB also supports sticky session by using cookies. The sticky sessions make sure that the traffic from a user is always routed to the same instance so that user gets seamless experience.
IPv6: CLB also support Internet Protocol version 6.
Operational Monitoring: We can also perform operational monitoring CLB and collect statistics on request count, latency etc. These metrics can be monitored in CloudWatch.
Main features of Application Load Balancer (ALB) are as follows:
AWS provides an option of creating a Placement Group in EC2 to logically group the instances within as single Availability Zone.
We get the benefits of low network latency and high network throughput by using a Placement Group.
Placement Group is a free option as of now. When we stop an instance, it will run in same Placement Group in restart at a later point of time.
The biggest limitation of Placement Group is that we cannot add Instances from multiple availability zones to one Placement Group.
Some of the possible connection issues with EC2 instance are:
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