change eip

setup_eip.rb

#!/usr/bin/ruby

require 'aws-sdk'

EIP_ADDR="XX.XX.XX.XX"
INSTANCE_ID='i-XXXXXXXX'
ec2_info = { 
  :access_key_id => ENV['AWS_KEY_ID'],
  :secret_access_key => ENV['AWS_SECRET_KEY']
}

ec2 = AWS::EC2.new(ec2_info)
eip = ec2.elastic_ips.find {|e| e.public_ip == EIP_ADDR}
eip.disassociate
eip.associate :instance => INSTANCE_ID