CIS 527

Lecture 8 - Puppet 2

Variables

$my_variable = "A bunch of text"
notify {$my_variable:}

Variable Notes

• Always starts with a dollar sign $
• Assign with an equals sign =
• Can hold strings, numbers, arrays, booleans, etc.
• Can use variables as any value inside a resource declaration, including the title

Variable Notes

• Variables are interpolated in double-quoted strings
  

  $username = "russfeld"
  notify {"Your home directory is /home/${username}": }

• Variables can only be assigned once

Learn More

• http://docs.puppetlabs.com/puppet/
  latest/reference/lang_variables.html


• http://docs.puppetlabs.com/puppet/
  latest/reference/lang_datatypes.html

Facts

• Puppet uses Facter to learn about systems
• Facter "facts" are stored as variables
• Facts can be used in manifest files

Facter

#> facter -p

Facter

#> facter -p

architecture => i386
bios_version => 6.00
block_devices => sda
domain => localdomain
id => root
...

Facter

List of facts

• http://docs.puppetlabs.com/facter/
  latest/core_facts.html
• You can also write your own if needed

Conditionals

if <boolean> {
    <code>
}
elsif <boolean> {
    <code>
} 
else {
    <code>
}

Booleans

$boolean = "false"
if $boolean {
    notify{"This is true":}
}
else {
    notify{"This is false":}
}

Booleans

$boolean = "false"
if $boolean {
    notify{"This is true":}
}
else {
    notify{"This is false":}
}

Notify: This is true

Booleans

• All facts are strings
• All non-empty strings are true
• Use str2bool(<string>)

Booleans

$boolean = "false"
if str2bool("$boolean") {
    notify{"This is true":}
}
else {
    notify{"This is false":}
}

Booleans

$boolean = "false"
if str2bool("$boolean") {
    notify{"This is true":}
}
else {
    notify{"This is false":}
}

Notify: This is false

Case Statement

case $operatingsystem {
  centos: { $apache = "httpd" }
  # Note that these matches 
  # are case-insensitive.
  redhat: { $apache = "httpd" }
  debian: { $apache = "apache2" }
  ubuntu: { $apache = "apache2" }
  default: { fail("Unrecognized OS") }
}

Case Statement

case $operatingsystem {
  centos, redhat: { $apache = "httpd" }
  debian, ubuntu: { $apache = "apache2" }
  default: { fail("Unrecognized OS") }
}

Can also use Regular Expressions

Case Statement

$apache = $operatingsystem ? {
  centos                => 'httpd',
  redhat                => 'httpd',
  /(?i)(ubuntu|debian)/ => 'apache2',
  default               => undef,
}

Classes

class my_class {
  notify {"This does something":}
}

include my_class

Classes

• Classes can contain any Puppet code
• Names must be all lowercase, with numbers and underscores allowed
• Classes are defined to make them available, and declared to be evaluated

Variable Scope

• Classes create a new variable scope
• Use $<class_name>::<var_name> to access
• They cannot be assigned outside the declaring class

Modules

• You can separate classes into modules for organization
• Each module has a specific file structure
• Modules are automatically loaded by Puppet from certain folders
• /etc/puppetlabs/puppet/puppet.conf

Module Structure

/etc/puppetlabs/puppet/modules/
  module_name/
    manifests/
      init.pp
    files/
    templates/
    lib/

Module Structure

• init.pp must contain a single class definition with the same name as the module
• Modules can contain other classes, files, and templates

Site Manifest

/etc/puppetlabs/puppet/manifests/site.pp

• Global manifest file for client/server
• Includes class / module declarations

include ntp
include apache
include mysql

Puppet Forge

• Lots of modules available free online
• http://forge.puppetlabs.com/
• Don't reinvent the wheel; make it better

Assignments

• Lab Help Session Friday 9 - 10 AM!
• Lab 2 - Configuration Management - Due Sunday, Feb 23th by 11:59 PM
• Automate configuration using Puppet
• Turn in:
  • CIS Transient Storage
  • via Storage Media in class Monday Feb 24th