Amazon Machine Images (AMI) provides the information required to launch an instance, which is a virtual server in the cloud. You must specify a source AMI when you launch an instance. You can launch multiple instances from a single AMI when you need multiple.
Here is how you can create an AMI from an instance from the command line.
aws ec2 create-image --instance-id i-0xxxxxxxxxxxxb --name "FrankfurtChrisinstance" --no-reboot
Note: What the no – reboot means
By default, Amazon EC2 attempts to shut down and reboot the instance before creating the image. If the 'No Reboot' option is set, Amazon EC2 doesn't shut down the instance before creating the image. When this option is used, file system integrity on the created image can't be guaranteed.