Creating AMIs with the No-Reboot Option in AWS

During the training, we discussed the implications of creating Amazon Machine Images (AMIs) with the No-Reboot option in AWS. Here's a summary of the key points:

AMI Creation with No-Reboot Option

Default Behavior: By default, when creating an AMI, AWS will shut down the EC2 instance to ensure file system integrity.
No-Reboot Option: If enabled, this option allows the creation of an AMI from a running EC2 instance without shutting it down.

Process Comparison

No-Reboot Disabled (Default)	No-Reboot Enabled
1. EC2 instance is shut down.	1. Snapshot is taken directly from the running EC2 instance.
2. EBS volume snapshot is taken.	2. AMI is created from the snapshot.
3. EBS snapshot is converted into an AMI.	-

Risks and Considerations

File System Integrity: Without a reboot, there is a risk that the file system may not be consistent.
Operating System Buffers: OS buffers may not be flushed to disk before snapshot creation, potentially leading to data inconsistency.
Use Case: It's crucial to understand the implications and ensure that the running state of the instance is suitable for a no-reboot AMI creation.

AWS Backup Service

Default Behavior: AWS Backup service does not reboot instances when taking EBS snapshots, so it inherently uses the no-reboot option.
File System Integrity: Using AWS Backup does not guarantee file system integrity since instances are not rebooted.

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Alternative: Scheduled AMI Backups with EventBridge and Lambda

EventBridge Rule: Create a schedule to invoke a Lambda function periodically (e.g., weekly).
Lambda Function: The function's code will create an AMI with the reboot option, ensuring file system integrity.
EC2 Instance Reboot: The instance will be rebooted, and an AMI will be created as per the schedule.

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