gistfile1.rb

#! /usr/bin/env ruby

=begin

  backshot.rb is a Ruby program driving 
  Amazon EBS <http://aws.amazon.com/ebs/> 
  to generate snapshots for backup purposes. 
  
  Hourly, daily, weekly, and monthly snapshots 
  are generated by default.
  
  Requires amazon-ec2 gem: 
  <http://github.com/grempe/amazon-ec2>
  
  To run this program configure your Amazon ID, key, and 
  choose which EBS volume to backup. Finally, add a 
  cron job to run this program hourly.
  
  A big thanks goes out to <http://chi.mp> 
  for sponsering this program.
  
  Copyright 2009 Darrin Eden

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  
=end

require 'rubygems'
require 'EC2'
require 'yaml'
require 'date'

ACCESS_KEY_ID = 'your access key'
SECRET_ACCESS_KEY = 'your secret key'
VOLUME = 'vol-01234567'
SNAPSHOTS = '/etc/snapshots.yml'

class Snapshots
  def snaps
    @snaps ||= {}
  end
  
  def units
    @units ||= {}
  end

  def create(unit_time)
    ec2 = EC2::Base.new( :access_key_id => ACCESS_KEY_ID, :secret_access_key => SECRET_ACCESS_KEY )
    previous = snaps[ unit_time ]
    snap = ec2.create_snapshot( :volume_id => VOLUME )
    snaps[ unit_time ] = snap.snapshotId
    units[ unit_time ] = DateTime.parse( snap.startTime ).send( unit_time )
    unless previous.nil?
      ec2.delete_snapshot( :snapshot_id => previous )
    end
  end
end

if File.exists?( SNAPSHOTS )
  shots = YAML::load_file( SNAPSHOTS )
else
  shots = Snapshots.new
end

%w(hour yday cweek month).each do |unit_time|
  unless shots.units[ unit_time] == DateTime.now.new_offset.send( unit_time )
    shots.create( unit_time )
  end
end

File.open( SNAPSHOTS, 'w' ) { |f| f.puts shots.to_yaml }