How to auto assign public ip to EC2 instance with boto

Question

I have to start a new machine with ec2.run_instances in a given subnet but also to have a public ip auto assigned (not fixed elastic ip).

When one starts a new machine from the Amazon's web EC2 Manager via the Request Instance (Instance details) there is a check-box called Assign Public IP to Auto-assign Public IP. See it highlighted in the screenshot:

How can I achieve that check-box functionality with boto?

Answer 1

Interestingly enough, seems that not many people had this problem. For me was very important to be able to do this right. Without this functionality one is not able to reach out to the internet from instances that are launched into a nondefault subnet.

The boto documentation provided no help, there was a related bug recently fixed, see at: https://github.com/boto/boto/pull/1705.

It's important to note that the subnet_id and the security groups have to be provided to the network interface NetworkInterfaceSpecification instead of run_instance.

import time
import boto
import boto.ec2.networkinterface

from settings.settings import AWS_ACCESS_GENERIC

ec2 = boto.connect_ec2(*AWS_ACCESS_GENERIC)

interface = boto.ec2.networkinterface.NetworkInterfaceSpecification(subnet_id='subnet-11d02d71',
                                                                    groups=['sg-0365c56d'],
                                                                    associate_public_ip_address=True)
interfaces = boto.ec2.networkinterface.NetworkInterfaceCollection(interface)

reservation = ec2.run_instances(image_id='ami-a1074dc8',
                                instance_type='t1.micro',
                                #the following two arguments are provided in the network_interface
                                #instead at the global level !!
                                #'security_group_ids': ['sg-0365c56d'],
                                #'subnet_id': 'subnet-11d02d71',
                                network_interfaces=interfaces,
                                key_name='keyPairName')

instance = reservation.instances[0]
instance.update()
while instance.state == "pending":
    print instance, instance.state
    time.sleep(5)
    instance.update()

instance.add_tag("Name", "some name")

print "done", instance

Answer 2

boto3 has NetworkInterfaces you can configure for DeviceIndex=0, and the Subnet and SecurityGroupIds should be moved from instance level to this block instead. Here's a working version for me,

def launch_instance(ami_id, name, type, size, ec2):
   rc = ec2.create_instances(
    ImageId=ami_id,
    MinCount=1,
    MaxCount=1,
    KeyName=key_name,
    InstanceType=size,
    NetworkInterfaces=[
        {
            'DeviceIndex': 0,
            'SubnetId': subnet,
            'AssociatePublicIpAddress': True,
            'Groups': sg
        },
    ]
   )

   instance_id = rc[0].id
   instance_name = name + '-' + type
   ec2.create_tags(
    Resources = [instance_id],
    Tags = [{'Key': 'Name', 'Value': instance_name}]
   )

   return (instance_id, instance_name)