If run as root on a server it will update the Yum repos to the latest, and then cleans up after itself

run.rb

require 'tempfile'
require 'fileutils'
require 'open3'

def edit_file(location, update_config)
  temp_file = Tempfile.new('newConfig')
  begin
    File.open(location, 'r') do |file|
      file.each_line do |line|
        if line.include? "="
          str_array = line.split("=")
          if str_array[0] == "mirrorlist" && update_config == true
            temp_file.puts "mirrorlist=http://repo.$awsregion.$awsdomain/latest/updates/mirror.list-$guid"
          elsif str_array[0] == "mirrorlist" && update_config == false
            temp_file.puts "mirrorlist=http://repo.$awsregion.$awsdomain/$releasever/updates/mirror.list-$guid"
          else
            temp_file.puts line
          end
        else
          temp_file.puts line
        end
      end
    end
    temp_file.close
    FileUtils.mv(temp_file.path, location)
  ensure
    temp_file.close
    temp_file.unlink
  end
end

def run_command(cmd_text)
  Open3.popen3(cmd_text) do |stdin, stdout, stderr, wait_thr|
    exit_status = wait_thr.value
    if exit_status != 0
      puts stderr.read
      abort
    else
      puts stdout.read
    end
  end
end

# In order we want to update the yum repos
# Then update the kernel
# Then revert the config
edit_file("/etc/yum.repos.d/amzn-main.repo",true)
edit_file("/etc/yum.repos.d/amzn-updates.repo",true)
run_command("yum update kernel -y")
edit_file("/etc/yum.repos.d/amzn-main.repo",false)
edit_file("/etc/yum.repos.d/amzn-updates.repo",false)