AWS CLI

A way to filter the output and get the only the required attributes is using a combination of filters,queries on the aws describe-images command as below:

aws ec2 describe-images \
--owners 'amazon' \
--filters 'Name=description,Values=Amazon Linux AMI*' \
--query 'sort_by(Images, &CreationDate)[-1].[ImageId]' \
--output 'text'

Command Explanation:

• owners : For images by amazon, use 'amazon'. To query your own images, use 'self'
• filters : You can use a list of filters to filter out the instance that you are looking for. I prefer description because I found the name filter missing for some images. Values support wildcards. More on filters
• query : Query can be used to filter only what is required from the output. You can also sort on fields that would be present in the output. I have sorted on the images and the creation date to get the last created image and filtered the ImageId
• output : Output can be json or text based on the way you plan to consume it.

Using Python

You can do the same using the below python script:

import boto3
from operator import itemgetter

client = boto3.client('ec2')
response = client.describe_images(
    Filters=[
        {
            'Name': 'description',
            'Values': [
                'Amazon Linux AMI*',
            ]
        },
    ],
    Owners=[
        'amazon'
    ]
)
# Sort on Creation date Desc
image_details = sorted(response['Images'],key=itemgetter('CreationDate'),reverse=True)
ami_id = image_details[0]['ImageId']

Update:

You can use fine-grain filters to get a quicker response. The filters mentioned in @Jack's answer work.

filters = [ {
    'Name': 'name',
    'Values': ['amzn-ami-hvm-*']
},{
    'Name': 'description',
    'Values': ['Amazon Linux AMI*']
},{
    'Name': 'architecture',
    'Values': ['x86_64']
},{
    'Name': 'owner-alias',
    'Values': ['amazon']
},{
    'Name': 'owner-id',
    'Values': ['137112412989']
},{
    'Name': 'state',
    'Values': ['available']
},{
    'Name': 'root-device-type',
    'Values': ['ebs']
},{
    'Name': 'virtualization-type',
    'Values': ['hvm']
},{
    'Name': 'hypervisor',
    'Values': ['xen']
},{
    'Name': 'image-type',
    'Values': ['machine']
} ]

# Use above filters 
response = client.describe_images(
  Filters=filters,
  Owners=[
      'amazon'
  ]
)

You can get AMI ID from aws site

Below is how to

To find a Linux AMI using the Images page

• Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

• From the navigation bar, select a region. You can select any region that's available to you, regardless of your location. This is the region in which you'll launch your instance.

• In the navigation pane, choose AMIs.

• (Optional) Use the Filter options to scope the list of displayed AMIs to see only the AMIs that interest you. For example, to list all Linux AMIs provided by AWS, select Public images. Choose the Search bar and select Owner from the menu, then select Amazon images. Choose the Search bar again to select Platform and then the operating system from the list provided.

• (Optional) Choose the Show/Hide Columns icon to select which image attributes to display, such as the root device type. Alternatively, you can select an AMI from the list and view its properties in the Details tab.

• The AMI ID for the platform and Distribution you have chosen would be in the AMI ID tab

More detail here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/finding-an-ami.html

I believe the simplest explanation is, than when people talk about AWS it implies that it is just one service.

In reality there are many AWS'es and it is one per region (originally they were completely disconnected, now it is a bit more complex). The global services, (for example IAM) typically live in us-east-1 (but that's abstracted from us).

This is why AMI you have different AMI IDs in different region. It is one image per AWS.