runonce

#Run Once

Table of Contents

1. Overview
2. Module Description - What the module does and why it is useful
3. Usage - Configuration options and additional functionality
4. Limitations - OS compatibility, etc.
5. Testing - Guide for contributing to the module

Overview

The run once module is a wrapper around exec. It ensures that a command is only ever executed once without having to explitily specifying $onlyif or $unless parameters.

##Module Description

The underlying implmentation uses semaphore lock files to control whether or not to run a command. An optional semaphore directory is created if it did not already exist, the command executed and the semaphore created upon success. Semaphores can either be persistent, by default residing in /var/lib/puppet/semaphores, or transient, residing in /tmp, and thus the command will be executed once per reboot.

Usage

runonce { 'hello-world':
  command => 'echo hello world!',
}

runonce { 'init-modules':
  command    => 'service kmod start',
  persistent => false,
}

Limitations

The current implmentation relies on /tmp being cleared by the underlying operating system on a reboot. Aditionally the persistent semaphore directory does not support parent directory creation.

Testing

This has been tested on Ubuntu LTS 12.04 and 14.04