Introduction:
Puppet is an open-source IT automation tool. The Puppet Domain Specific Language (DSL) (gives you an operating-system-independent language) 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 keep them there.
puppet resource user root /*The puppet resource command should be used to inspect user root*/
puppet describe user | less */Man pages to understand the different attributes and value for defining a manifest.*/
Some of the type of resources are
(->)User
(->)File
(->)Package
(->)Service
(->)Cron
(->)Group
Resource Abstraction Layer or RAL */Puppet will remove the complexity of managing the resources across different operating systems. You can sit back and watch whether puppet uses apt, yum, rpm*/
puppet apply -e "user" { 'galatea': ensure => 'present', } /*puppet one-liner.The user galatea should exist on the system*/
Syntax:
'resource'{ 'title':
attribute => 'value',
}
puppet resource -e user galatea /*Edit the resource user manifest. The user galatea should have the comment Galatea of Cyprus*/
Classes and Manifests
-Manifests:
- A manifest is a text file that contains puppet code. And is appended by .pp
- It's the same stuff you see using the `puppet resource tool` and applied with the `puppet apply`
- In theory, you could put whatever bits and pieces of syntactically valid Puppet code you like into a manifest.
- A key aspect of proper manifest management is related to Puppet classes.
-Classes:
- In puppet's DSL a class is a named block of Puppet code.
- A class will generally manage a set of resources related to a single function or system component
- Class often contain other classes
- Using a Puppet class requires two steps. First, you'll need to define it by writing a class definition and saving it in a manifest file. When Puppet runs, it will parse this manifest and store your class definition. The class can then be declared to apply it to nodes in your infrastructure.
- Classes are Singleton, which means that a class can be declared once on a given node.In this sense, Puppet's classes are different than the kind of classes you may have encountered in Object Oriented programming, which are often instantiated multiple times.
Validation Tools:
- The `puppet parser` tool can be used to check the syntax of your manifest before doing `puppet apply`
- puppet parser validate cowsayings/manifests/cowsay.pp
Before applying a puppet note on
"SCOPE": Below is an example of sample class module (under the path /etc/puppetlabs/puppet/environment/production/modules/cowsayings/manifests/) called cowsay.pp.
class cowsayings::cowsay {
package {'cowsay' :
ensure => 'present',
}
}
In the above class definition,
- "cowsaying::" this SCOPE syntax definition tells Puppet where to find that class; in this case, it's in the cowsayings module.
- Usually the Puppet recognizes the "/etc/puppetlabs/puppet/environment/production/modules/cowsayings/manifest/init.pp" manifest to contain the "main" class for the module. Just like below example:
class cowsayings {
include cowsayings::cowsay
include cowsayings::fortune
}
Remove the already installed packages namely "fortune-mod" and "cowsay" using the one-liner below and install using the puppet apply of manifest /etc/puppetlabs/puppet/environment/production/modules/cowsayings/test/init.pp". In init.pp the class are declared.
# puppet apply -e "package { 'fortune-mod':ensure => 'absent',} package { 'cowsay':ensure => 'absent',}"
# puppet apply --verbose /etc/puppetlabs/puppet/environments/production/modules/cowsayings/tests/init.pp
Please feel free to add in comments if you face any difficulties. I will be happy to help you.
