Digital Ocean dynamic dns DIY. Script which updates your DO domain records when public IP changes. Useful for services running in home office.

update-dns.rb

#!/usr/bin/env ruby
require 'json' 

####MODIFY THESE#####
DOMAIN="example.com"
RECORDNAME="subdomain"
API_KEY="thahh4aevi4poophuM1eish5rashi4xoo9hoo5fish8Pie6jaekoquahy3phagoh" #This is not real api key :P
####MODIFY THESE#####


#####SCRIPT STARTS#######

##
# Super safe way to get external ip in unix system with curl installed
##

#Get external IP from untrusted source, but there's so many of them that so one should work
ip_echo_domains = ["http://wtfismyip.com/text","http://api.ipify.org/","http://ipecho.net/plain","http://icanhazip.com"]
ip_array = []
ip_echo_domains.each do |domain|
  result = `curl #{domain}`
  next unless result.length.between?(7,15) and result.count('.') == 3 # result is something between '8.8.8.8' and '123.123.123.132'
  ip_array << result 
end
#Hash frequencys and take the result with highest freq 
freq = ip_array.inject(Hash.new(0)) { |h,v| h[v] += 1; h }
ip = ip_array.max_by { |v| freq[v] }

#Get list of my domain records
json_response = `curl -H "Authorization: Bearer #{API_KEY}" -H "Content-Type: application/json" \
                 -X GET "https://api.digitalocean.com/v2/domains/#{DOMAIN}/records"`
my_records = JSON.parse(json_response)['domain_record']

record_id = ''
my_records.each do |record|
  if record['type'] == 'A' && record['name'] == RECORDNAME
    exit 0 if record['data'] == ip #Exit if it hasn't changed
    record_id = record['id']
    break
  end
end

#Update Domain Record
json_response =`curl -X PUT "https://api.digitalocean.com/v2/domains/#{DOMAIN}/records/#{record_id}" \
  -d\'{"data":\"#{ip}\"}\' \
  -H "Authorization: Bearer #{API_KEY}" \
  -H "Content-Type: application/json"`
record = JSON.parse(json_response)['domain_record']
if record['data'] != ip
  puts "Updating #{RECORDNAME}.#{DOMAIN} failed"
  exit 100
else
  puts "Updated #{RECORDNAME}.#{DOMAIN} succesfully"
end

Here's an alternative I wrote, which I think is much more secure.

https://github.com/benyanke/configScripts/tree/master/dns-update-server

In this case, the DO api key only exists on a single central API server with this script, and every other host can connect to this api server to inform it of it's IP. This means your DO keys (which provide complete access to your DO account) are not spread around on multiple hosts.

my_records = JSON.parse(json_response)['domain_record'] -> my_records = JSON.parse(json_response)['domain_records']