Skip to content

Instantly share code, notes, and snippets.

What would you like to do?
Update AWS instance hosts file with all internal dns names for VPC members. Useful when dns discovery is not useable/available.
#!/usr/bin/env python
import boto3
import requests
ec2 = boto3.resource('ec2')
# fetch the instance id
response = requests.get('')
instance_id = response.text
# fetch the vpc_id
current_instance = ec2.Instance(instance_id)
vpc_id = current_instance.vpc_id
# loop through all instances, and get their details
hosts = []
for i in ec2.instances.all():
if i.vpc_id != vpc_id:
# append both the full hostname, as well as the short hostname
hosts.append("%s %s\n" % (i.private_ip_address, i.private_dns_name))
hosts.append("%s %s\n" % (i.private_ip_address, i.private_dns_name.split('.')[0]))
# open the current hosts file, read the first 3 lines, and append the new hosts
with open('/etc/hosts', 'r') as f:
lines = f.readlines()
start = lines[0:3]
new_lines = start + hosts
new_contents = "".join(new_lines)
with open('/etc/hosts', 'w') as f:
print new_contents
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment