Writing a papply script

We'd like to make it as quick and easy as possible to apply Puppet on a machine, so I usually write a little script that wraps the puppet apply command with the parameters it needs. And to deploy the script where it's needed, what better tool than Puppet itself?

How to do it...

Follow these steps:

1. In your Puppet repo, create the directories needed for a puppet module:

   ubuntu@cookbook:~/puppet$ mkdir modules
   ubuntu@cookbook:~/puppet$ mkdir modules/puppet
   ubuntu@cookbook:~/puppet$ mkdir modules/puppet/manifests
   ubuntu@cookbook:~/puppet$ mkdir modules/puppet/files 
   

2. Create the file modules/puppet/files/papply.sh with the following contents (change the path /home/ubuntu/puppet to where your Puppet repo is located). The sudo puppet apply command should all be on one line:

   #!/bin/sh
   sudo puppet apply /home/ubuntu/puppet/manifests/site.pp
     --modulepath=/home/ubuntu/puppet/modules/ $*

3. Create the file modules/puppet/manifests/init.pp with the following contents:

   class puppet {
     file { '/usr/local/bin/papply':
       source => 'puppet:///modules/puppet/papply.sh',
       mode   => '0755',
     }
   }

4. Modify your manifests/nodes.pp file as follows:

   node 'cookbook' {
     include puppet
   }

5. Apply your changes:

   ubuntu@cookbook:~/puppet$ sudo puppet apply manifests/site.pp
     --modulepath=/home/ubuntu/puppet/modules
   Notice: /Stage[main]/Puppet/File[/usr/local/bin/papply]
     /ensure: defined content as '{md5}
       171896840d39664c00909eb8cf47a53c'
   Notice: Finished catalog run in 0.07 seconds
   

6. Test that the script works:

   ubuntu@cookbook:~/puppet$ papply
   Notice: Finished catalog run in 0.07 seconds
   

Now whenever you need to run Puppet, you can simply run papply. In future, when we apply Puppet changes, I'll ask you to run papply instead of the full puppet apply command.

How it works...

As you've seen, to run Puppet on a machine and apply a specified manifest file, we use the puppet apply command:

puppet apply manifests/site.pp

When you're using modules (such as the puppet module we just created) you also need to tell Puppet where to search for modules, using the modulepath argument:

puppet apply manifests/nodes.pp --
  modulepath=/home/ubuntu/puppet/modules

In order to run Puppet with the root privileges it needs, we have to put sudo before everything:

sudo puppet apply manifests/nodes.pp --
  modulepath=/home/ubuntu/puppet/modules

Finally, any additional arguments passed to papply will be passed through to Puppet itself, by adding the $* parameter:

sudo puppet apply manifests/nodes.pp --
  modulepath=/home/ubuntu/puppet/modules $*

That's a lot of typing, so putting this in a script makes sense. We've added a Puppet file resource that will deploy the script to /usr/local/bin and make it executable:

file { '/usr/local/bin/papply':
  source => 'puppet:///modules/puppet/papply.sh',
  mode   => '0755',
}

Finally, we include the puppet module in our node declaration for cookbook:

node 'cookbook' {
  include puppet
}

You can do the same for any other nodes managed by Puppet.