Knife Ec2 Hostname Script - for Chef

ec2_hostname.rb

#!/usr/bin/env ruby

# This script is intended to preprocess a knife ec2 server create command and 
# generate a user_data script in the /tmp folder that will rename the host
# to match whatever the node name is before the chef bootstrapping process
# begins.  It then splits the knife command in front of the --node-name or -N
# options and inserts "--user-data /tmp/server-01.userdata" (in the example 
# below) and execs the command.
# 
# Usage:
# ec2_hostname knife ec2 server create --node-name server-01 --run-list 'role[awesome]' --whatever honey-badgers


require "erb"

class Ec2Hostname

  def go(argv=ARGV)
    node_name_index = argv.index('--node-name') || argv.index('-N')
    @hostname       = argv[(node_name_index+1)]
    @domain         = 'airtime.com'
    user_data_path  = "/tmp/#{@hostname}.userdata"

    File.open(user_data_path, 'w') do |f|
      f.write ERB.new(DATA.read).result(binding)
    end

    argv.insert(node_name_index, user_data_path)
    argv.insert(node_name_index, '--user-data')

    safe = argv.map do |arg|
      case arg
      when /[\]\[]/
        "\"#{arg.gsub(',','","')}\""
      else
        arg
      end
    end

    puts safe.join(' ')
    exec safe.join(' ')
  end
end
Ec2Hostname.new.go(ARGV)

__END__
#!/bin/bash

# Replace this with your domain
DOMAIN="<%= @domain %>"

HOSTNAME="<%= @hostname %>"
IPV4=`/usr/bin/curl -s http://169.254.169.254/latest/meta-data/public-ipv4`

# Set the host name
hostname $HOSTNAME
echo $HOSTNAME >> /etc/hostname

# Add fqdn to hosts file
echo "# Start of ec2_hostname modifications
127.0.0.1 localhost

$IPV4 $HOSTNAME.$DOMAIN $HOSTNAME

# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts
# End of ec2_hostname modifications
" > /etc/hosts