如何使用 boto3 获取我的 ec2 实例的 arn

Question

I want the arn of all my ec2 instances. The describe_instances() does not give out the instances. Is there any other method or some way that may list out all the arns as well. I need them to be stored in a database,also I'm working on sample instances for now,this eventually needs to work for multiple accounts as well. So, a solution that will work throughout will be helpful.

Answer 1

You can recreate it yourself:

arn:aws:ec2:<REGION>:<ACCOUNT_ID>:instance/<instance-id>

For this purpose, I think you can even use * as and <ACCOUNT_ID>, and it will work.

for more info you can see this question

Actually instances['Reservations'][0]['Instances'] may not have all instances. Instances are grouped together by security groups.Different security groups means many list elements will be there. To get every instance in that region, you need to use the code below.

Note: ['Reservations'][0]['Instances'] doesn't list all the instances, It only gives you the instances which are grouped by the first security group. If there are many groups you won't get all instances.

import boto3
region = 'ap-south-1'

ec2 = boto3.client('ec2', region_name=region)

def list_instances():
    instance_ids = []
    response = ec2.describe_instances(Filters=[{'Name': 'instance-type', 'Values': ["t2.micro", "t3.micro"]}])
    instances_full_details = response['Reservations']
    for instance_detail in instances_full_details:
        group_instances = instance_detail['Instances']

        for instance in group_instances:
            instance_id = instance['InstanceId']
            instance_ids.append(instance_id)
    return instance_ids

instance_ids = list_instances()
print(instance_ids)

Answer 2

You can construct it yourself. In short it is:

sts = boto3.client('sts')

region = boto3.Session().region_name

instance_id='id-3324234'

account_id = sts.get_caller_identity()['Account']

instance_arn=f"arn:aws:ec2:{region}:{account_id}:instance/{instance_id}"

print(instance_arn)

But to be pedantic and get AWS partition as well it would be:

def get_partition_for_region(session):
    # based on https://github.com/boto/botocore/pull/1715
    region_name = session.region_name
    partitions = session.get_available_partitions()
    for partition in partitions:
        regions = session.get_available_regions('stepfunctions', partition)
        if region_name in regions:
            return partition
    # use the default aws partition in case nothing is found
    return 'aws'
  
partition = get_partition_for_region(boto3.Session())

sts = boto3.client('sts')

region = boto3.Session().region_name

instance_id='id-3324234'

account_id = sts.get_caller_identity()['Account']

instance_arn=f"arn:{partition}:ec2:{region}:{account_id}:instance/{instance_id}"

print(instance_arn)