How to specify root volume size of core-os ec2 instance using boto3?

Question

I cannot figure out from documentation and source code how to define size of the root device.

You can specify N additional block devices using BlockDeviceMappings sectio

Answer 1

Ran into this issue myself today, probably to late for the original poster, but in case anyone else stumbles across this question later I did the following:

import boto3
ec2 = boto3.resource('ec2',
                     region_name='eu-west-1',
                     aws_access_key_id='my-key',
                     aws_secret_access_key='my-secret')
instance = ec2.create_instances(ImageId='my-image-id',
                                BlockDeviceMappings=[{"DeviceName": "/dev/xvda","Ebs" : { "VolumeSize" : 50 }}])

The above has been truncated (you'll need to pass more arguments to create_instances for other values, InstanceType etc.) but essentially pass the root device (/dev/xvda in this case) in as part of the BlockDeviceMappings value with the desired volume size (50GB in the above example).

Answer 2

Same as Steve Jeffereies has mentioned, naming the DeviceName is the key. I was able to use /dev/sda1 which you would usually see on AWS console. The following is a working example using magnetic,

BlockDeviceMappings=[
    {
        'DeviceName': '/dev/sda1',
        'Ebs': {
            'VolumeSize': 30,
            'VolumeType': 'standard'
        }
    }
]

Answer 3

Follow is minimal required fields that have to be set the size of the root device:

import boto3
ec2_resource = boto3.resource('ec2')
    reservations = ec2_resource.create_instances(

        ImageId= "ami-xyz",
        MinCount=1,
        MaxCount=1,
        InstanceType='xyz',
        KeyName='key-pair',
        TagSpecifications=[
            {
                'ResourceType': 'instance',
                'Tags': [{
                     'Key': 'Name',
                    'Value': 'xyz-machine'
                }]
            }
        ],
        IamInstanceProfile={
        'Name':'xyz-role'
        },
        BlockDeviceMappings=[
            {
                'DeviceName': '/dev/sda1',
                'Ebs': {
                    'VolumeSize': 30,
                    'VolumeType': 'standard'
                }
            }
        ]
    )

Answer 4

See Stackoverflow: How to launch EC2 instance with Boto, specifying size of EBS?

Also, here's a way to do it from the AWS Command-Line Interface (CLI):

aws ec2 run-instances --image-id ami-xxxxxxxx --instance-type m1.xlarge --block-device-mappings '{"DeviceName": "/dev/sda1","Ebs" : { "VolumeSize" : 50 }}'