lab-05.1-Resource-purging

Lab 5.1: Resource purging

If we think about the set of a certain type of resources on our system as being part of a list, we can tell Puppet that we want to explicitly manage the whole set. In other words, if Puppet isn't managing a resource in that set then it will be removed. This clearly only works when that set is a list of finite length, such as the list of packages or the list of users.

There is a finite set of host records stored in /etc/hosts. Create a Puppet manifest that represents them using the output of a puppet resource command. Then use a resources resource to purge unmanaged host entries and experiment to see the effects this has.

If you damage the hosts file and cannot reach the master, let the instructor know and they will help you restore it.

Tip: You can redirect the output of a command to a file, if it'sconvenient. For example, puppet resource host > hosts.pp.

Change the current working directory to the environmentpath

cd $(puppet agent --configprint environmentpath)/production/modules

Create the system module

1. Create a new PDK module called system

   $ pdk new module

   You will see several questions requiring an answer. Enter these answers:

   Replace the “N” in these answers with your student number (for example, student8).

   Question	Answer
   Module Name	system
   Forge Name	studentN
   Credit author	Student N
   License	Apache-2.0
   Operating systems	RedHat

2. Press Y to generate the module in the current directory.

3. Change the current working directory to the module you created.

   cd system

Resource purging

1. Gather the current hosts by running puppet resource host

2. Turn the output of the current hosts into a Puppet class file.

   • pdk new class hosts
   • Edit manifests/hosts.pp
   • Paste the output of the puppet resource host command into the class.

3. Add a resources resource to the class.

   • Set the purge => true attribute.

4. Validate and test the new class.

   pdk validate

5. Commit your changes to the repo.

   • Init your module: git init
   • Add the origin: git remote add origin git@gitlab.classroom.puppet.com:puppet/system.git
   • Checkout the branch: git checkout -b studentN
   • Add the files: git add --all
   • Create a commit: git commit -m "Initial Commit"
   • Push the commit to the Git server: git push origin studentN

6. Change directories to [control-repo]

   • Edit the Puppetfile and uncomment out these lines.

     mod 'system',
       :git => 'git@gitlab.classroom.puppet.com:puppet/system.git',
       :branch => 'studentN'
     

7. Commit and push your control repo changes, using the git add/commit/push sequence.

Log in to the Puppet Enterprise console and classify your new class

1. Point your browser at https://classXXXX-master.classroom.puppet.com/

2. Enter the credentials:

   • username: studentN
   • password: puppetlabs

3. In the left menu, under CONFIGURE, click Classification

4. Open All Environments and your studentN-env

5. Click on the Configuration tab

6. Under Classes section, Add new class type in system::hosts and Add class

7. Click Commit 1 change in the lower right corner.

Observe purging

1. Add a new entry in /etc/hosts named removeme.puppetlabs.vm

   • Add 1.2.3.4 removeme.puppetlabs.vm

   Sample /etc/hosts file:

   127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
   ::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
   
   10.120.0.235 puppet.classroom.puppet.com puppet
   10.120.0.51 gitlab.classroom.puppet.com gitlab gitlab.puppet.vm
   1.2.3.4 removeme.puppetlabs.vm
   

2. Run puppet to purge your change: puppet agent -t Expected output:

   [root@1905nix0 control-repo]# puppet agent -t
   ...
   Info: Caching catalog for 1905nix0.classroom.puppet.com
   Info: Applying configuration version 'puppet-student0-5862f9c2c38'
   Notice: /Stage[main]/System::Hosts/Host[removeme.puppetlabs.vm]/ensure: removed
   Info: Computing checksum on file /etc/hosts
   Notice: Applied catalog in 0.29 seconds
   

Solution

Your module structure should resemble

[root@training modules]# tree system/
system/
├── examples
│   └── hosts.pp
└── manifests
    └── hosts.pp

Example file: system/manifests/hosts.pp

class system::hosts {
  resources {'host':
    purge => true,
  }
  host { 'master.puppetlabs.vm':
    ensure       => present,
    host_aliases => ['master'],
    ip           => '192.168.X.X', ## use the classroom IP
  }
  host { 'localhost':
    ensure       => present,
    host_aliases => [
                      'localhost.localdomain',
                      'localhost4',
                      'localhost4.localdomain4',
                      'training.puppetlabs.vm',
                      'training'
                    ],
    ip           => '127.0.0.1',
  }

## Use your own IP, or the ::ipaddress fact
  host { 'yourname.puppetlabs.vm':
    ensure       => present,
    host_aliases => ['yourname'],
    ip           => $::ipaddress,
  }
}

Example file: system/examples/hosts.pp

include system::hosts

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