Q: What is an Amazon Machine Image (AMI)?
A: An Amazon Machine Image (AMI) is a template that contains a software configuration (operating system, application server, and applications) which is used to create a virtual machine within the Amazon Elastic Compute Cloud (EC2). An AMI includes the following:
- A template for the root volume required for an instance (for example, an operating system, an application server, and applications).
- Launch permissions that control which AWS accounts can use the AMI to launch instances.
- A block device mapping that specifies the volumes to attach to the instance when it's launched.
Q: How do I create an AMI?
A: You can create an AMI from an existing EC2 instance by following these steps:
-
Prepare the instance:
- Make sure your instance is in a state suitable for creating an image (e.g., stop the instance if necessary).
-
Create the AMI:
- Use the AWS Management Console, AWS CLI, or SDKs.
Example (AWS CLI):
aws ec2 create-image --instance-id i-1234567890abcdef0 --name "My server" --no-reboot
This command creates an AMI from the instance with the ID i-1234567890abcdef0 and names it "My server".
Q: How do I launch an instance from an AMI?
A: You can launch an instance from an AMI using the AWS Management Console, AWS CLI, or SDKs.
Example (AWS CLI):
aws ec2 run-instances --image-id ami-0abcdef1234567890 --instance-type t2.micro --key-name MyKeyPair --security-groups my-sg
This command launches an instance using the AMI with the ID ami-0abcdef1234567890, of type t2.micro, with the specified key pair and security group.
Q: How do I share an AMI with another AWS account?
A: You can share an AMI by modifying its launch permissions.
Example (AWS CLI):
aws ec2 modify-image-attribute --image-id ami-0abcdef1234567890 --launch-permission "{\"Add\":[{\"UserId\":\"123456789012\"}]}"
This command shares the AMI with the ID ami-0abcdef1234567890 with the AWS account 123456789012.
Q: How do I copy an AMI to another region?
A: You can copy an AMI to another region using the AWS Management Console, AWS CLI, or SDKs.
Example (AWS CLI):
aws ec2 copy-image --source-image-id ami-0abcdef1234567890 --source-region us-west-2 --region us-east-1 --name "My copied AMI"
This command copies the AMI with the ID ami-0abcdef1234567890 from the us-west-2 region to the us-east-1 region and names the copied AMI "My copied AMI".
Q: How do I deregister an AMI?
A: Deregistering an AMI makes it unavailable for launching new instances.
Example (AWS CLI):
aws ec2 deregister-image --image-id ami-0abcdef1234567890
This command deregisters the AMI with the ID ami-0abcdef1234567890.
Q: Can I update an existing AMI?
A: No, you cannot update an existing AMI. However, you can launch an instance from the AMI, make the necessary updates to the instance, and then create a new AMI from the updated instance.
Q: What is the difference between an AMI and a snapshot?
A:
- AMI: An AMI is a complete image of a virtual machine, including the operating system, application server, and applications. It can be used to launch new instances.
- Snapshot: A snapshot is a backup of an EBS volume at a point in time. It can be used to create new volumes or restore existing volumes.
Q: How do I find public AMIs?
A: You can find public AMIs in the AWS Marketplace or by using the AWS Management Console or AWS CLI to search for AMIs.
Example (AWS CLI):
aws ec2 describe-images --owners amazon --filters "Name=architecture,Values=x86_64" "Name=root-device-type,Values=ebs"
This command lists the AMIs owned by Amazon that have an x86_64 architecture and use EBS volumes.
Q: How do I tag an AMI?
A: You can add tags to an AMI to help organize and manage your AMIs.
Example (AWS CLI):
aws ec2 create-tags --resources ami-0abcdef1234567890 --tags Key=Name,Value=MyAMI
This command tags the AMI with the ID ami-0abcdef1234567890 with a tag Name=MyAMI.
Important Interview Questions and Answers on AWS AMI
Q: What is an AMI in AWS?
An Amazon Machine Image (AMI) is a template that contains a software configuration (operating system, application server, and applications) used to launch instances in the AWS environment. It includes information such as:
- A template for the root volume of the instance.
- Launch permissions that control which AWS accounts can use the AMI to launch instances.
- A block device mapping that specifies the volumes to attach to the instance when it is launched.
Q: How do you create an AMI?
To create an AMI, follow these steps:
- Launch an instance from an existing AMI.
- Customize the instance by installing software and configuring settings.
- Stop the instance (optional but recommended).
- Create an image from the instance using the AWS Management Console, CLI, or SDK.
Example using AWS CLI:
aws ec2 create-image --instance-id i-1234567890abcdef0 --name "My server" --no-reboot
Q: What are the types of AMIs?
- EBS-backed AMIs: The root device for an instance launched from the AMI is an Amazon EBS volume created from an Amazon EBS snapshot.
- Instance Store-backed AMIs: The root device for an instance launched from the AMI is an instance store volume created from a template stored in Amazon S3.
Q: What is the difference between an EBS-backed and Instance Store-backed AMI?
- EBS-backed AMI: The root volume is an EBS volume. It allows for stopping the instance and saving the state.
- Instance Store-backed AMI: The root volume is an instance store. Data on an instance store volume persists only during the lifetime of the instance. If the instance is stopped or terminated, the data is lost.
Q: How can you copy an AMI to another region?
You can copy an AMI to another region using the AWS Management Console, CLI, or SDK.
Example using AWS CLI:
aws ec2 copy-image --source-image-id ami-12345678 --source-region us-west-1 --region us-east-1 --name "My AMI copy"
Q: How do you share an AMI with another AWS account?
- Modify the permissions of the AMI to allow another AWS account to use it.
- Share the associated snapshots.
Example using AWS CLI:
aws ec2 modify-image-attribute --image-id ami-12345678 --launch-permission "Add=[{UserId=123456789012}]"
Q: What is a golden AMI and why is it important?
A golden AMI is a pre-configured AMI that includes the necessary security patches, software, and configurations required for an application to run. It ensures consistency, security, and compliance across environments by standardizing the base images used to launch instances.
Q: Can you update an AMI?
No, you cannot update an existing AMI. Instead, you must launch an instance from the AMI, apply the updates, and then create a new AMI from the updated instance.
Q: How do you automate the creation of AMIs?
You can automate the creation of AMIs using AWS Lambda, AWS Step Functions, and AWS Systems Manager (SSM). You can also use infrastructure-as-code tools like AWS CloudFormation or HashiCorp Terraform.
Example using AWS Systems Manager Automation:
AWSTemplateFormatVersion: '2010-09-09'
Resources:
AMICreationAutomation:
Type: "AWS::SSM::Automation"
Properties:
DocumentName: "AWS-UpdateLinuxAmi"
DocumentVersion: "1"
TargetType: "/AWS::EC2::Instance"
Parameters:
AutomationAssumeRole:
Default: "arn:aws:iam::123456789012:role/AWSAutomationRole"
SourceAMIId:
Default: "ami-12345678"
InstanceType:
Default: "t2.micro"
Q: What are some best practices for managing AMIs?
- Tagging: Use consistent tagging for AMIs for easy identification and management.
- Versioning: Maintain versions of AMIs to track changes and roll back if necessary.
- Lifecycle Management: Implement lifecycle policies to clean up old and unused AMIs to save costs.
- Security: Ensure that AMIs are regularly updated with security patches and configurations.
- Testing: Thoroughly test AMIs before using them in production environments.
