Interview questions on Amazon aws

Interview questions on EC2 (Elastic Compute Cloud)

Quest:- What is instance in EC2 ? what are the types?

Ans :-    Instance is EBS backed virtual machine.Meaning that root volume is an EBS backed     volume. Their are 3 types of instances 1) Spot instances 2) On Demanad  3) Reserved Instances.

Quest:- What is EBS volume?

Ans :-    EBS stands for Elastic Block Store.Which provides persistent block level storage volumes     for use with Amazon EC2 instances in the AWS Cloud. It provides high availability and durability . Also avoids disk failures.

Quest:- How to attach and mount EBS volume to EC2 instance?

Ans  :-  Open the Amazon EC2 console. Click Volumes in the navigation pane. Select a volume and then click Attach Volume. In the Attach Volume dialog box, start typing the name or ID of the instance to attach the volume to in the Instance box, and select it from the list of suggestion options (only instances in the same Availability Zone as the volume are displayed).

Attaching EBS :- Connect to your instance using SSH. Depending on the block device driver of the kernel, the device might be attached with a different name than what you specify. For example, if you specify a device name of/dev/sdh, your device might be renamed /dev/xvdh or /dev/hdh by the kernel;Use the lsblk command to view your available disk devices and their mount points . Determine whether you need to create a file system on the volume. Use the sudo file -s device ( e.g. /dev/xvdf) command to list special information, such as file system type. Use the  command  sudo mkfs -t ext4 device_name to create an ext4 file system on the volume.Use the command sudo mkdir mount_point to create a mount point directory for the volume. Use the  command sudo mount device_name mount_point to mount the volume at the location you just created. Create a backup of your /etc/fstab file that you can use if you accidentally destroy or delete this file while you are editing it. Open the /etc/fstab file using your favorite text editor, such as nano or vim . Add a new line to the end of the file for your volume using the following format.

device_name  mount_point  file_system_type  fs_mntops  fs_freq  fs_passno

Quest:- What is the difference between "STOP" and "TERMINATE"?

Ans :-   There is a difference between "stop" and "terminate". If you "stop" an instance that is backed by EBS then the information on the root volume will still be in the same state when you "start"   the machine again. If you "terminate" the machine, then even if it is backed by EBS it is gone.

Quest:- What is AMI?
Ans :-   AMI stands for Amazon Machine Image. AMI is a special type of virtual appliance that is used    to instantiate (create) a virtual machine within the Amazon Elastic Compute Cloud ("EC2").                It serves as the basic unit of deployment for services delivered using EC2.

Quest :- How to create AMI from EC2 instance?
Ans: -    Login to your AWS account. Select the region in which your instances are. Right-click the instance that you would like to use as the basis for your AMI. Click Create Image (EBS AMI) on the context menu.In the Create Image dialog box, provide a unique name and a description. Click OK. It may take a few minutes for the AMI to be created. Once it is created, it will appear in the AMIs view in AWS Explorer.

Quest :- What is snapshot ? How to create snapshot of ebs volume?
Ans :-    Snapshots are incremental backups, which means that only the blocks on the device that have changed after your most recent snapshot are saved. When you delete a snapshot, only the data exclusive to thatsnapshot is removed. 

After writing data to an Amazon EBS volume, you can periodically create a snapshot of the volume to use as a baseline for new volumes or for data backup. If you make periodic snapshots of a volume, the snapshots are incremental so that only the blocks on the device that have changed after your last snapshot are saved in the new snapshot. Even though snapshots are saved incrementally, the snapshot deletion process is designed so that you need to retain only the most recent snapshot in order to restore the volume.

Snapshots occur asynchronously and the status of the snapshot is pending until the snapshot is complete.

To create a snapshot using the console

Open the Amazon EC2 console. Click Snapshots in the navigation pane. Click Create Snapshot. In the Create Snapshot dialog box, select the volume to create a snapshot for, and then click Create.