I know everyone and there mother has written one of these, so I guess I’m now my mother.  Run this as a cron to enable a pretty cheapo dynamic DNS via Slicehost.  You’ll need the ActiveResource gem to use it.

#! /usr/bin/env ruby

# */5 * * * * /usr/bin/dynamicdns.rb

require 'rubygems'

require 'activeresource'

require 'open-uri'

# Configure your stuff

@api_key      = 'YOUR_API_KEY'

@record_id    = 1337 #the record ID you are updating

@ttl          = 10 * 60 #ten minutes, yeah sure.

@record_type  = 'A'

@record_name  = 'vpn'

@ip_site      = 'http://checkip.dyndns.org/'

@ip_path      = '/tmp/lastip'

@log          = '/tmp/lastip.log'

API_SITE      = "https://#{@api_key}@api.slicehost.com/"

class Record < ActiveResource::Base;self.site = API_SITE;end;

# Check the last ip address

@last_ip = File.exist?(@ip_path) ? File.read(@ip_path).strip : ''

begin

@ip = open(@ip_site){|f| f.read}.match(/[0-9.]+/)[0]

rescue Exception

File.open(@log,'a+'){|f| f.puts "#{Time.now} [ERROR] - Failed to open #{@ip_site}"}

exit(1)

end

# Update the email address

if @ip != @last_ip

File.open(@ip_path,'w+'){|f| f.puts @ip}

record = Record.find(@record_id)

record.name = @record_name

record.record_type = @record_type

record.data = @ip

record.ttl  = @ttl

record.save

File.open(@log,'a+'){|f| f.puts "#{Time.now} [INFO] - IP updated: #{@ip}"}

else

File.open(@log,'a+'){|f| f.puts "#{Time.now} [INFO] - IP did not change"}

end