Chef file lock to enforce only one chef run

gistfile1.rb

# Putting this at the top of your "base" recipe or some common recipe that
# is loaded very early on will force Chef to only run one process at a time.
# This is enforced using a file lock. The file lock is automatically released
# when the process exits, so there is no need to explicitly do so.

#----------------------------------------------------------------------
# Obtain File Lock
#----------------------------------------------------------------------
$_chef_lock_file = File.open(File.join(Chef::Config[:file_cache_path], "chef_lock"), "w+")
if $_chef_lock_file.flock(File::LOCK_EX | File::LOCK_NB) === false
  Chef::Log.info("Another Chef process running. Not running.")
  exit(true)
end