Learning Puppet
Quick Start Guide
Suhan Dharmasuriya
Software Engineer - Test Automation
WSO2 Inc.

Outline
● What is puppet?
● Session 1 - Configuring puppet master/agent
● Puppet module fundamentals
● What are puppet templates?
● Session 2 - Puppet modules and templates
● Session 3 - Looping elements in a given template

What is puppet?
"The Puppet Domain Specific Language (DSL) is a
Ruby-based coding language that provides a precise and
adaptable way to describe a desired state for each
machine in your infrastructure. Once you've described a
desired state, Puppet does the work to bring your systems
in line and keeping them there" - Puppet Labs
Q: Why not use shell scripts and manage infrastructure?
- Not feasible to manage large # of nodes

Installing Puppet Master and Agent
Puppet Master
● sudo apt-get update
● sudo apt-get install puppetmaster
● /etc/puppet/puppet.conf
[main]
dns_alt_names=puppetmaster,puppet,puppet.example.com
[master]
autosign=true
● /etc/hosts
127.0.0.1 localhost
127.0.0.1 puppetmaster
● /etc/hostname
puppetmaster
dns_alt_names are mentioned so that when
creating ssl certificates for the master itself, the
names will be embedded to the certificate itself
which is easy for the agent to find out that
agent is connecting to the intended puppet
master.
autosign=true is used to automatically sign
puppet agent join requests for the time being.
So that you can easily learn puppet and later
comment out the said line to manually sign
agent certificates.
SESSION1

Installing Puppet Master and Agent
Puppet Agent
● sudo apt-get update
● sudo apt-get install puppet
● /etc/puppet/puppet.conf
[main]
server = puppet
● /etc/hosts
127.0.0.1 localhost
127.0.1.1 agent1
192.168.92.2 puppet
● /etc/hostname
agent1
IP address of the Puppet master
SESSION1
If you get certificate issues, using puppet cert
command clean and regenerate the
certificates accordingly.
> puppet cert clean <host>
> puppet cert generate <host>

Do a puppet agent catalog run
● Add the following to /etc/puppet/manifests/site.pp
node default {
}
● Since we have established the master/agent communication
previously, go to puppet agent and issue the following,
> puppet agent --test OR
> puppet agent -t
You will see an output as follows.
root@agent1:~# puppet agent --test
info: Caching catalog for agent1.domain.name
info: Applying configuration version '1416123976'
notice: Finished catalog run in 0.01 seconds
Puppet always starts compiling with either a
single manifest file or a directory of manifests
that get treated like a single file.
This main starting point is called the main
manifest or site manifest.
SESSION1
The name default (without quotes) is a special value for node
names. If no node statement matching a given node can be
found, the default node will be used.

Do a puppet agent catalog run
> puppet cert list --all
+ "agent1.us-west-2.compute.internal" (SHA256)
B4:DC:3C:FF:DF:D6:36:C7:1E:49:CE:99:17:E9:55:89:42:0E:3A:DB:67:84
:4F:D0:7B:FE:7E:E4:2D:BE:8C:D4
+ "puppetmaster.us-west-2.compute.internal" (SHA256)
58:EF:90:05:72:1C:51:8F:BC:63:6C:5E:30:11:87:AC:04:28:F5:F3:94:F3
:0A:DA:91:05:00:ED:5A:7A:E7:9E (alt names: "DNS:puppet",
"DNS:puppet.us-west-2.compute.internal", "DNS:puppetmaster",
"DNS:puppetmaster.us-west-2.compute.internal")
SESSION1

Do a puppet agent catalog run
HTTP trace at puppet master node /var/log/puppet/masterhttp.log
When puppet agent connect to master and get the
certificate auto signed for the first time
When a puppet agent catalog run is performed,
> puppet agent -t
{
{

module is simply a directory tree with a specific, predictable structure
modules
|_your_module
|_ manifests
|_ templates
|_yourtemplate.erb
|_ files
|__ facts.d
|__ examples
|__ spec
|__ lib
Puppet module fundamentals
This outermost directory’s name matches the name of the module
Contains all of the manifests in the module
- init.pp — Contains a class definition. This class’s name
must match the module’s name.
- other_class.pp — Contains a class named
your_module::other_class.
- my_defined_type.pp — Contains a defined type named
your_module::my_defined_type.
- implementation/ — This directory’s name affects the class
names beneath it.
- foo.pp — Contains a class named
your_module::implementation::foo.
- bar.pp — Contains a class named
your_module::implementation::barContains plugins, like custom facts and
custom resource types.
Contains templates, which the module’s manifests can use.
- component.erb — A manifest can render this template with
template('your_module/component.erb').
- component.epp — A manifest can render this template with
epp('your_module/component.epp').
Contains static files, which managed nodes can download
- service.conf — This file’s source => URL would be
puppet:///modules/your_module/service.conf. Its contents
can also be accessed with the file function, like content =>
file('your_module/service.conf').
Contains external facts, which are an alternative to Ruby-based
custom facts. These will be synced to all agent nodes, so they can
submit values for those facts to the Puppet master
Contains spec tests for any plugins in
the lib directory
Contains examples showing how to
declare the module’s classes and
defined types
- init.pp
- other_example.pp

What are puppet templates?
$value = template("your_module/yourtemplate.erb")
Puppet assumes that,
● Template files are stored in the templates directory inside your
puppet module
● common modulepath is at /etc/puppet/modules
/etc/
|__ puppet
|__ manifests
| |__ site.pp
|__ modules
|__ your_module
|__ manifests
|__ templates
|__ yourtemplate.erb
/etc/puppet/modules/your_module/templates/yourtemplate.erb
Templates can be used to specify the contents of
files. They are commonly used to template out
configuration files, filling in variables with the
managed node’s facts.
Puppet supports templates written in the ERB
templating language, which is part of the Ruby
standard library.
Embedded Puppet template (EPP)

Using Puppet modules and templates
● puppet agent → agent1
● create puppet module → myserver, create init.pp, template files
/etc/
|__ puppet
|__ manifests
| |__ site.pp
|__ modules
|__ myserver
|__ manifests
|__init.pp
|__params.pp
|__ templates
|__ welcome-template-file.erb
/etc/puppet/manifests/site.pp
import 'myserver'
node 'agent1' {
include myserver
}
node default {
}
SESSION2
Contains the class definition. This class’s
name must match the module’s name
When we include the module in site.pp
manifest file, puppet looks into this init.pp
script and execute
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2
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We are importing the myserver module to our main manifest:
site.pp
Then we are including it to our agent1 puppet node definition

Using Puppet modules and templates
/etc/puppet/modules/myserver/manifests/init.pp
class myserver inherits myserver::params{
file { "/tmp/$myname":
ensure => file,
content => template('myserver/welcome-template-file.erb'),
}
}
/etc/puppet/modules/myserver/manifests/params.pp [1]
class myserver::params {
$say_hello_to = 'guys and gals'
$myname = 'welcome file.xml'
}
SESSION2
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Image Credits: https://docs.puppetlabs.com/puppet/latest/reference/modules_fundamentals.html#manifests
Image Credits: https://docs.puppetlabs.com/puppet/latest/reference/modules_fundamentals.html#templates

Using Puppet modules and templates
/etc/puppet/modules/myserver/templates/welcome-template-file.erb
<% if @say_hello_to -%>
Hello <%= @say_hello_to %>,
<% end -%>
I'm <%= @myname %>, on a <%= @operatingsystem %> system, nice to
meet you.
Then issue the following command on puppet agent node.
> puppet agent -t
A file will be created on agent node.
/tmp/welcome file.xml
Hello guys and gals,
I'm welcome file.xml, on a Ubuntu system, nice to meet you.
SESSION2
4
Wondering how value came for @operatingsystem?
Apart from custom variables defined, puppet can use variables
predefined by Factor.

Looping elements in a given template
/etc/puppet/manifests/site.pp to be modified as follows,
class myserver::params {
$say_hello_to = 'guys and gals'
$myname = 'welcome file.xml'
$members = ['10.0.1.196', '10.0.1.198', '10.0.1.200']
}
Append the following to the /etc/puppet/modules/myserver/templates/welcome-
template-file.erb
<members>
<%- if @members -%>
# loop hostnames
<%- @members.each do |hostname| -%>
<member>
<hostName><%= hostname %></hostName>
<port>4100</port>
</member>
<%- end -%>
<%- end -%>
</members>
SESSION3
loop variable
each — Repeat a block of
code any number of times,
using a collection of values
to provide different
parameters each time.

Looping elements in a given template
Then issue the following command on puppet agent node.
> puppet agent -t
/tmp/welcome file.xml will now look like this.
Hello guys and gals,
I'm welcome file.xml, on a Ubuntu system, nice to meet you.
<members>
<member>
<hostName>10.0.1.196</hostName>
<port>4100</port>
</member>
<member>
<hostName>10.0.1.198</hostName>
<port>4100</port>
</member>
<member>
<hostName>10.0.1.200</hostName>
<port>4100</port>
</member>
</members>
SESSION3

Looping elements in a given template
Now lets try to parameterize both member and port.
Modify /etc/puppet/manifests/site.pp as follows,
class myserver::params {
$say_hello_to = 'guys and gals'
$myname = 'welcome file.xml'
$members = { '192.168.1.156' => '4100',
'192.168.1.157' => '4000' }
}
Modify the following <members> section in
/etc/puppet/modules/myserver/templates/welcome-template-file.erb
<members>
<%- if @members -%>
<%- @members.each_pair do |hostname,port| -%>
<member>
<hostName><%= hostname %></hostName>
<port><%= port %></port>
</member>
<%- end -%>
<%- end -%>
</members>
SESSION3
two loop
variables
[example]

Looping elements in a given template
Then issue the following command on puppet agent node.
> puppet agent -t
/tmp/welcome file.xml will now look like this.
Hello guys and gals,
I'm welcome file.xml, on a Ubuntu system, nice to meet you.
<members>
<member>
<hostName>192.168.1.156</hostName>
<port>4100</port>
</member>
<member>
<hostName>192.168.1.157</hostName>
<port>4000</port>
</member>
</members>
SESSION3

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