Simple script to update SSH config file from AutoScaling groups

ec2ssh_update.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

"""Update SSH config file from AutoScaling groups

Author: NamNV609
Copyright: 2022, NamNV609
Homepage: https://github.com/namnv609
"""

import subprocess
import json
import os

def exec_aws_cmd(cmd):
  aws_response = subprocess.run(cmd, stdout=subprocess.PIPE)

  return json.loads(aws_response.stdout.decode("utf-8"))

ssh_config_file = "/home/{username}/.ssh/config".format(username=os.environ.get("USER"))
bak_ssh_config_file = ssh_config_file + "_old"

print("-> Backup {current} to {bak} ...".format(current=ssh_config_file, bak=bak_ssh_config_file))
if os.path.isfile(ssh_config_file):
  subprocess.run(["cp", "-f", ssh_config_file, bak_ssh_config_file], stdout=subprocess.PIPE)
print("-> Backup done!")

asg_names = []
ssh_config_content = []

for asg_name in asg_names:
  print("-> Get instances for autoscaling group {asg_name} ...".format(asg_name=asg_name))
  auto_scaling_groups = exec_aws_cmd(["aws", "autoscaling", "describe-auto-scaling-groups", "--auto-scaling-group-name", asg_name])
  print("-> Get instances done!")

  for instance in auto_scaling_groups["AutoScalingGroups"][0]["Instances"]:
    instance_id = instance["InstanceId"]

    print("-> Get private ip for {instance_id}".format(instance_id=instance_id))
    instance_data = exec_aws_cmd(["aws", "ec2", "describe-instances", "--instance-ids", instance_id])
    private_ip = instance_data["Reservations"][0]["Instances"][0]["PrivateIpAddress"]
    print("-> Get private ip done!")

    ssh_config_content.append("Host {asg_name}-{private_ip}".format(asg_name=asg_name, private_ip=private_ip))
    ssh_config_content.append("  HostName {private_ip}".format(private_ip=private_ip))

ssh_config_content.append("")

print("Update ssh config file ...")
ssh_config = open(ssh_config_file, "w")
ssh_config.write("\n".join(ssh_config_content))
ssh_config.close()
print("Update done. Here is config content:")
print("========================================")
print("\n".join(ssh_config_content))