aws_swap.rb

# Script to setup swap space on a Amazon AWS instance
# Takes about 1 minute per GB of swap size
# run it like this: 
# ruby aws_swap.rb 4G

SWAP_LOCATION = "/mnt/swapfile"

def run(cmd)
  if ARGV.join(' ').include?('-p')
    puts cmd
  else
    %x(#{cmd})
  end
end

def in_bytes(number)
  if number.include?('G')
    number.to_i*1024*1024
  elsif number.include?('M')
    number.to_i*1024
  else
    number
  end
end

puts "Mounting /mnt"
run("sudo mount /mnt")
puts "Wrinting #{ARGV[0]} of zeroes to #{SWAP_LOCATION}"
run("sudo dd if=/dev/zero of=#{SWAP_LOCATION} bs=1024 count=#{in_bytes(ARGV[0])}")
puts "Formatting and activating swap"
run("sudo sudo mkswap #{SWAP_LOCATION}")
run("sudo swapon #{SWAP_LOCATION}")
puts run("swapon -s")