Writing a papply script

We'd like to make it as quick and easy as possible to apply Puppet on a machine; for this we'll write a little script that wraps the puppet apply command with the parameters it needs. We'll deploy the script where it's needed with Puppet itself.

How to do it...

Follow these steps:

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

   t@mylaptop ~$ cd puppet/modules
   t@mylaptop modules$ mkdir -p puppet/{manifests,files}
   

2. Create the modules/puppet/files/papply.sh file with the following contents:

   #!/bin/sh sudo puppet apply /etc/puppet/cookbook/manifests/site.pp \--modulepath=/etc/puppet/cookbook/modules $*

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

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

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

   node default {
     include base
     include puppet
   }

5. Add the Puppet module to the Git repository and commit the change as follows:

   t@mylaptop puppet$ git add manifests/site.pp modules/puppet
   t@mylaptop puppet$ git status
   On branch master
   Your branch is up-to-date with 'origin/master'.
   Changes to be committed:
    (use "git reset HEAD <file>..." to unstage)
   modified: manifests/site.pp
   new file: modules/puppet/files/papply.sh
   new file: modules/puppet/manifests/init.pp
   t@mylaptop puppet$ git commit -m "adding puppet module to include papply"
   [master 7c2e3d5] adding puppet module to include papply
    3 files changed, 11 insertions(+)
    create mode 100644 modules/puppet/files/papply.sh
    create mode 100644 modules/puppet/manifests/init.pp
   

6. Now remember to push the changes to the Git repository on git.example.com:

   t@mylaptop puppet$ git push origin master Counting objects: 14, done. Delta compression using up to 4 threads. Compressing objects: 100% (7/7), done. Writing objects: 100% (10/10), 894 bytes | 0 bytes/s, done. Total 10 (delta 0), reused 0 (delta 0) To git@git.example.com:repos/puppet.git 23e887c..7c2e3d5 master -> master
   

7. Pull the latest version of the Git repository to your new node (testnode for me) as shown in the following command line:

   root@testnode ~# sudo -iu puppet
   puppet@testnode ~$ cd /etc/puppet/cookbook/puppet@testnode /etc/puppet/cookbook$ git pull origin master remote: Counting objects: 14, done. remote: Compressing objects: 100% (7/7), done. remote: Total 10 (delta 0), reused 0 (delta 0) Unpacking objects: 100% (10/10), done. From git.example.com:repos/puppet * branch master -> FETCH_HEAD Updating 23e887c..7c2e3d5 Fast-forward manifests/site.pp | 1 + modules/puppet/files/papply.sh | 4 ++++ modules/puppet/manifests/init.pp | 6 ++++++ 3 files changed, 11 insertions(+), 0 deletions(-) create mode 100644 modules/puppet/files/papply.sh create mode 100644 modules/puppet/manifests/init.pp
   

8. Apply the manifest manually once to install the papply script:

   root@testnode ~# puppet apply /etc/puppet/cookbook/manifests/site.pp --modulepath /etc/puppet/cookbook/modules
   Notice: Compiled catalog for testnode.example.com in environment production in 0.13 seconds
   Notice: /Stage[main]/Puppet/File[/usr/local/bin/papply]/ensure: defined content as '{md5}d5c2cdd359306dd6e6441e6fb96e5ef7'
   Notice: Finished catalog run in 0.13 seconds
   

9. Finally, test the script:

   root@testnode ~# papply
   Notice: Compiled catalog for testnode.example.com in environment production in 0.13 seconds
   Notice: Finished catalog run in 0.09 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 default node declaration:

node default {
  include base
  include puppet
}

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