RH294 - ch03s02

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Guided Exercise: Managing Variables

In this exercise, you will define and use variables in a playbook.

Outcomes

You should be able to:

Define variables in a playbook.
Create tasks that use defined variables.

On workstation, run the lab data-variables start command. This function creates the data-variables working directory, and populates it with an Ansible configuration file and host inventory.

[student@workstation ~]$ lab data-variables start

Procedure 3.1. Instructions

On workstation, as the student user, change into the /home/student/data-variables directory.
```
[student@workstation ~]$ cd ~/data-variables
[student@workstation data-variables]$
```

Over the next several steps, you will create a playbook that installs the Apache web server and opens the ports for the service to be reachable. The playbook queries the web server to ensure it is up and running.

Create the playbook.yml playbook and define the following variables in the vars section:

Table 3.2. Variables

Variable	Description
`web_pkg`	Web server package to install.
`firewall_pkg`	Firewall package to install.
`web_service`	Web service to manage.
`firewall_service`	Firewall service to manage.
`python_pkg`	Required package for the `uri` module.
`rule`	The service name to open.

---
- name: Deploy and start Apache HTTPD service
  hosts: webserver
  vars:
    web_pkg: httpd
    firewall_pkg: firewalld
    web_service: httpd
    firewall_service: firewalld
    python_pkg: python3-PyMySQL
    rule: http

Create the tasks block and create the first task, which should use the yum module to make sure the latest versions of the required packages are installed.
```
  tasks:
    - name: Required packages are installed and up to date
      yum:
        name:
          - "{{ web_pkg }}"
          - "{{ firewall_pkg }}"
          - "{{ python_pkg }}"
        state: latest
```
Note
You can use ansible-doc yum to review the syntax for the yum module. The syntax shows that its name directive can take a list of packages that the module should work with, so that you do not need separate tasks to makes sure each package is up-to-date.
Create two tasks to make sure that the httpd and firewalld services are started and enabled.
```
    - name: The {{ firewall_service }} service is started and enabled
      service:
        name: "{{ firewall_service }}"
        enabled: true
        state: started

    - name: The {{ web_service }} service is started and enabled
      service:
        name: "{{ web_service }}"
        enabled: true
        state: started
```
Note
The service module works differently from the yum module, as documented by ansible-doc service. Its name directive takes the name of exactly one service to work with.
You can write a single task that ensures both services are started and enabled, using the loop keyword covered later in this course.

Add a task that ensures specific content exists in the /var/www/html/index.html file.

    - name: Web content is in place
      copy:
        content: "Example web content"
        dest: /var/www/html/index.html

Add a task that uses the firewalld module to ensure the firewall ports are open for the firewalld service named in the rule variable.

    - name: The firewall port for {{ rule }} is open
      firewalld:
        service: "{{ rule }}"
        permanent: true
        immediate: true
        state: enabled

Create a new play that queries the web service to ensure everything has been correctly configured. It should run on localhost. Because of that Ansible fact, Ansible does not have to change identity, so set the become module to false. You can use the uri module to check a URL. For this task, check for a status code of 200 to confirm the web server on servera.lab.example.com is running and correctly configured.
```
- name: Verify the Apache service
  hosts: localhost
  become: false
  tasks:
    - name: Ensure the webserver is reachable
      uri:
        url: http://servera.lab.example.com
        status_code: 200
```

When completed, the playbook should appear as follows. Review the playbook and confirm that both plays are correct.

---
- name: Deploy and start Apache HTTPD service
  hosts: webserver
  vars:
    web_pkg: httpd
    firewall_pkg: firewalld
    web_service: httpd
    firewall_service: firewalld
    python_pkg: python3-PyMySQL
    rule: http

  tasks:
    - name: Required packages are installed and up to date
      yum:
        name:
          - "{{ web_pkg  }}"
          - "{{ firewall_pkg }}"
          - "{{ python_pkg }}"
        state: latest

    - name: The {{ firewall_service }} service is started and enabled
      service:
        name: "{{ firewall_service }}"
        enabled: true
        state: started

    - name: The {{ web_service }} service is started and enabled
      service:
        name: "{{ web_service }}"
        enabled: true
        state: started

    - name: Web content is in place
      copy:
        content: "Example web content"
        dest: /var/www/html/index.html

    - name: The firewall port for {{ rule }} is open
      firewalld:
        service: "{{ rule }}"
        permanent: true
        immediate: true
        state: enabled

- name: Verify the Apache service
  hosts: localhost
  become: false
  tasks:
    - name: Ensure the webserver is reachable
      uri:
        url: http://servera.lab.example.com
        status_code: 200

Before you run the playbook, use the ansible-playbook --syntax-check command to verify its syntax. If it reports any errors, correct them before moving to the next step. You should see output similar to the following:
```
[student@workstation data-variables]$ ansible-playbook --syntax-check playbook.yml

playbook: playbook.yml
```

Use the ansible-playbook command to run the playbook. Watch the output as Ansible installs the packages, starts and enables the services, and ensures the web server is reachable.

[student@workstation data-variables]$ ansible-playbook playbook.yml

PLAY [Deploy and start Apache HTTPD service] ***********************************

TASK [Gathering Facts] *********************************************************
ok: [servera.lab.example.com]

TASK [Required packages are installed and up to date] **************************
changed: [servera.lab.example.com]

TASK [The firewalld service is started and enabled] ****************************
ok: [servera.lab.example.com]

TASK [The httpd service is started and enabled] ********************************
changed: [servera.lab.example.com]

TASK [Web content is in place] *************************************************
changed: [servera.lab.example.com]

TASK [The firewall port for http is open] **************************************
changed: [servera.lab.example.com]

PLAY [Verify the Apache service] ***********************************************

TASK [Gathering Facts] *********************************************************
ok: [localhost]

TASK [Ensure the webserver is reachable] ***************************************
ok: [localhost]

PLAY RECAP *********************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0
servera.lab.example.com    : ok=6    changed=4    unreachable=0    failed=0

Finish

On workstation, run the lab data-variables finish script to clean up this exercise.

[student@workstation ~]$ lab data-variables finish

This concludes the guided exercise.

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Red Hat Linux Automation with Ansible (RH294)

Haley_Ruccio

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Learn how to automate Linux system administration tasks with Red Hat Ansible Automation PlatformRed Hat Enterprise Linux Automation with Ansible (RH294) is designed for Linux administrators and developers who need to automate repeatable and error-prone steps for system provisioning, configuration, application deployment, and orchestration. This course is based on Red Hat® Enterprise Linux® 9 and Red Hat Ansible Automation Platform 2.2.Course content summaryInstall Red Hat Ansible Automation Platform on control nodes.Create and update inventories of managed hosts and manage connections to them.Automate administration tasks with Ansible Playbooks and ad hoc commands.Write effective playbooks at scale.Protect sensitive data used by Ansible Automation Platform with Ansible Vault.Reuse code and simplify playbook development with Ansible Roles and Ansible Content Collections.Audience for this courseThis course is geared toward Linux system administrators, DevOps engineers, infrastructure automation engineers, and systems design engineers who are responsible for these tasks:Automating configuration managementEnsuring consistent and repeatable application deploymentProvisioning and deployment of development, testing, and production serversIntegrating with DevOps continuous integration/continuous delivery workflowsPrerequisites for this coursePass the Red Hat Certified System Administrator (RHCSA) exam (EX200), or demonstrate equivalent Red Hat Enterprise Linux knowledge and experience.Take our free assessment to gauge whether this offering is the best fit for your skills.

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curl finds no route to host?

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I am doing the self-paced course RH294 . With two exercises (Ch.3 final Lab and Ch.4 lab exercise 2) I ran into this problem:after installing and starting a web service, from the classroom web termicaI I cannot reach servera.lab.example.com with curl: "No route to host". This despite the fact that I can ping it, open a shell to it, and install the package on it with Ansible.Anyone else have the same problem?What might be the cause?

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Welcome to the Red Hat Linux Automation with Ansible (RH294) group in the Red Hat Learning Community

cschunke

18 lip 2023

We are excited to launch a space dedicated to the Red Hat Training course Red Hat Linux Automation with Ansible! To gain the most value from this group - click the "Join Group" button in the upper right hand corner.We encourage group members to collaborate in this group to discuss topics, ask questions, share best practices and tips, provide course feedback, and share their accomplishments as it relates to RH294.Read more about Red Hat Linux Automation with Ansible here.

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Revision: rh294-8.4-9cb53f0

Red Hat Enterprise Linux Automation with Ansible

Guided Exercise: Managing Variables

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