Evaluating ERB templates

Evaluating ERB templates that are in a template file

Put template files in the templates directory of a module. ERB files use the .erb extension.

To use a ERB template file, evaluate it with the template function. For example:

# template(<FILE REFERENCE>, [<ADDITIONAL FILES>, ...])
file { '/etc/ntp.conf':
  ensure  => file,
  content => template('ntp/ntp.conf.erb'),
  # Loads /etc/puppetlabs/code/environments/production/modules/ntp/templates/ntp.conf.erb
}

The first argument to the function is the file reference: a string in the form '<MODULE>/<FILE>', which loads <FILE> from <MODULE>’s templates directory. For example, the file reference activemq/amq/activemq.xml.erb loads the <MODULES DIRECTORY>/activemq/templates/amq/activemq.xml.erb file.

The template function can take any number of additional template files, and concatenate their outputs together to produce the final string.

Evaluating ERB template strings

If you have a string value that contains template content, you can evaluate it with the inline_template function.

In older versions of Puppet, inline templates were mostly used to get around limitations — tiny Ruby fragments were useful for transforming and manipulating data before Puppet had iteration functions like map or puppetlabs/stdlib functions like chomp and keys.

In modern versions of Puppet, inline templates are usable in some of the same situations template files are. Because the heredoc syntax makes it easy to write large and complicated strings in a manifest, you can use inline_erb to reduce the number of files needed for a simple module that manages a small config file.

For example:

$ntp_conf_template = @(END)
...template content goes here...
END

# inline_template(<TEMPLATE STRING>, [<ADDITIONAL STRINGS>, ...])
file { '/etc/ntp.conf':
  ensure  => file,
  content => inline_template($ntp_conf_template),
}

The inline_template function can take any number of additional template strings, and concatenate their outputs together to produce the final value.