Get latest AMI ID for AWS instance

Question

I wanted to fetch the latest ami id for AWS Linux machine while creating an ec2 instance for an autoscaling architecture.

I was trying the aws cli to get the images types, but it would print out a lot of information if I used the describe-images command.

My requirement was to get only the image id, so that I could use it to create a launch configuration or launch an instance with the latest ami-id.

Answer 1

A little-known recent feature is the ability to Query for the latest Amazon Linux AMI IDs using AWS Systems Manager Parameter Store | AWS Compute Blog.

The namespace is made up of two parts:

• Parameter Store Prefix (tree): /aws/service/ami-amazon-linux-latest/
• AMI name alias: (example) amzn-ami-hvm-x86_64-gp2

These:

aws ec2 describe-images --owners amazon --filters "Name=name,Values=amzn*" --query 'sort_by(Images, &CreationDate)[].Name'

Get-EC2ImageByName -Name amzn* | Sort-Object CreationDate | Select-Object Name

can be changed into:

aws ssm get-parameters --names /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2 --region us-east-1 

Get-SSMParameter -Name /aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2 -region us-east-1

Plus, it can be used in a CloudFormation template:

# Use public Systems Manager Parameter
 Parameters :
 LatestAmiId :
 Type : 'AWS::SSM::Parameter::Value<AWS::EC2::Image::Id>'
 Default: ‘/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2’

Resources :
 Instance :
 Type : 'AWS::EC2::Instance'
 Properties :
 ImageId : !Ref LatestAmiId

Answer 2

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'
  ]
)