Puppet 4 :: Working with Files and Templates

• Andrew Mallet
• ERB: Embedded Ruby Language (any version of puppet). Uses ruby code within tags and require basic ruby knowledge. Variables begin with @ symbol.
  • template = read a template
  • inline_template = read a string

$down_time = '23:00'
$motd = @(END)
Welcome to the server: <%= @facts['networking']['fqdn'] %>
The server will be shutdown today at: <%= @down_time %>
END

file { 'etc/motd'
  ensure => 'file',
  content => inline_template($motd),
}

• EPP: Embedded Puppet (Requires Version 4 +). Uses puppet expressions within tags and easier validation tools.
  • epp = read a template
  • inline_epp = read a string

$motd = @(END)
Welcome to the server: <%= $facts['networking']['fqdn'] %>
The server will be shutdown today at: <%= $down_time %>
END

file { 'etc/motd'
  ensure => 'file',
  content => inline_epp($motd, {'down_time' => '17:00' }, ),
}

Working with ERB Templates

• located in the /templates/ directory
• Create ntp.conf.erb file

# Managed by Puppet - do not edit
server <%= @ntp_local_server %> iburst prefer
server <%= @nto_regional_server %>
driftfile /var/lib/ntp/drift

• Setting variables

#ntp/manifests/admin_file.pp

$ntp_regional_server = $ntp_location ? {
  'london' => 'uk.pool.ntp.org',
  'paris' => 'uk.pool.ntp.org',
  'nyc' => 'uk.pool.ntp.org',
  default => 'pool.ntp.org',
}
$ntp_local_server = '192.168.0.0'

#usage
file { $title :
  content => template('ntp/ntp.conf.erb')       # assumes the template directory so no need to mention
  ...
}

• Admin.pp file

define ntp:admin_file ( $ntp_location = 'london' ) {
  $ntp_regional_server = $ntp_location ? {
    'london' => 'uk.pool.ntp.org',
    'paris' => 'fr.pool.ntp.org',
    'nyc' => 'us.pool.ntp.org',
    default => 'pool.ntp.org',
  }
  $ntp_local_server = '192.168.0.0'

  file { $title :
    content => template('ntp/ntp.conf.erb'),      # assumes the template directory so no need to mention
    owner => 'root',
    group => 'admingroup',
    ensure => file,
  }
}

# usage
class ntp::config ( $location = 'london' ) {
  ntp::admin_file { '/etc/ntp.conf':
    ntp_location => $location,
  }
}

• Logic with non-printing tags

# if
<% if @monitor == false -%>
  disable monitor
<% end -%>

# loop (each)
$ntp_regional_server = $ntp_location ? {
  'london' => ['uk.pool.ntp.org', 'ie.pool.ntp.org'],
  'paris' => ['fr.pool.ntp.org', 'de.pool.ntp.org'],
  'nyc' => ['us.pool.ntp.org', 'ca.pool.ntp.org'],
  default => ['uk.ntp.org', 'us.pool.ntp.org'],
}
<% @ntp_regional_server.each do |s| -%>
  server <%= s %>
<% end -%>

• Validating ERB templates (mainly on ruby env not on puppet env) - Syntax Check
  • we need to use the 'erb' and the ruby command
  • In /opt/puppetlabs/puppet/bin path. set PATH variable #global
  • ./erb -PxT '-' <template.erb> | ./ruby -c #relative path

<%= ... %>   # Expression tags
<% ... -%>   # Ruby Code

Working with EPP templates

• Variables

# Managed by Puppet - do not edit
server <%= $ntp_local_server %> iburst prefer

• Logic with non-printing tags

# if
<% unless $monitor == true { -%>
  disable monitor
<% } -%>

• Iteration

# The "-" at the end suppresses the line feed. Ensure that no characters are there after -%> (not even an empty space)
<% $ntp_regional_server.each |$server| { -%>
  server <%= $server %>
<% } -%>

• Usage

$monitor = false
$ntp_regional_server = $ntp_location ? {
  'london' => 'uk.pool.ntp.org',
  'paris' => 'fr.pool.ntp.org',
  'nyc' => 'us.pool.ntp.org',
  default => 'pool.ntp.org',
}
$ntp_local_server = '192.168.0.0'

 file { $title :
    content => epp('ntp/ntp.conf.erb', {'monitor' => $monitor, 'ntp_local_server' => $ntp_local_server, 'ntp_regional_server' => $ntp_regional_server, } ),
    owner => 'root',
    group => 'admingroup',
    ensure => file,
  }

• Validating EPP templates: puppet epp validate <EPP file>
• Validate & Render EPP templates: puppet epp validate <EPP file> --values '{ m => 3, param => value}'

Delivering Files with Puppet

• Purging Resources

resources { 'host' :
  purge => true,    # host resources that are not managed by puppet will be removed
  noop => true,     # no-operation. Not going to do anything. (remove after development?)
}

# usage
class host_entries {
  host { 'localhost':
    ip => '127.0.0.1',
  }
  host { $facts['networking']['fqdn']:               # this also centos so error. on other system this should work fine.
    ip => $facts['networking']['ip'],
  }
  
  host { 'centos7':             #2.0 error: Duplicate declaration Host[centos]. Fix check before creating (usign unless)
    ip => '192.168.56.15',
  }

  resources { 'host':
    purge => true,
  }
}

# puppet apply-e 'include host_entries'

• Encapsulating logic in Defined Types

define host_entries::host_entry ( $ip, ) {
  unless $facts['netowrking']['fqdn'] == $title {
    host { $title :
      ip => $ip,
    }
  }
}

class host_entries {
  host { 'localhost':
    ip => '127.0.0.1',
  }
  host { $facts['networking']['fqdn']:
    ip => $facts['networking']['ip'],
  }
  
  host_entries::host_entry { 'ubuntu':
    ip => '192.168.56.16',
  }
  host_entries:;host_entry { 'centos7':
    ip => '192.168.56.15',
  }

  resources { 'host':
    purge => true,
  }
}

• any manual entry to etc/hosts file other than puppet will be removed on the next puppet run because of "purge=>true"