Registering Variables

Registering Variables#

You can create variables from the output of an Ansible task using the register keyword. These registered variables can be used in subsequent tasks within your playbook. Additionally, you can use the debug module to print statements during execution, which is useful for debugging variables or expressions.

Example#

Let’s add NTP server configuration to a device.

  1. Add NTP Server Configuration in host_vars File

Create a file named host_vars/172.16.10.14 and add the following content:

# host_vars/172.16.10.14
---
ospf:
  process_id: 10
  router_id: 1.1.1.1
  networks:
    - network: 9.9.9.8
      mask: 0.0.0.3
    - network: 192.168.71.0
      mask: 0.0.0.255

ntp:
  servers:
    - 3.3.3.3
    - 4.4.4.4
    - 5.5.5.5

  1. Create an NTP Template File

Create a file named ntp.j2 in the templates directory with the following content:

{% for server in ntp.servers %}
ntp server {{ server }}
{% endfor %}

  1. Create a Playbook

Create a playbook for registering the variable and printing the result:

---
- name: "Playbook - Register Variable"
  hosts: 172.16.10.14
  gather_facts: false

  tasks:
    - name: "NTP Configuration"
      cisco.ios.ios_config:
        src: "ntp.j2"
      register: ntp_output

    - name: "Print NTP Result"
      ansible.builtin.debug:
        msg: "{{ ntp_output }}"

Explanation#

  • NTP Configuration Task: This task applies the NTP configuration using the ios_config module and registers the output in the variable ntp_output.

  • Print NTP Result Task: This task uses the debug module to print the content of the ntp_output variable, showing what commands were executed.

Viewing the Output#

After running the playbook, the output will be displayed in your terminal, showing the commands that were executed.

(.venv) ➜ ansible-cbt-lab git:(main) ✗ ansible-playbook playbook/register_variable.yaml

PLAY [Playbook - Register Variable] *****************************************************

TASK [NTP Configuration] ****************************************************************

TASK [Print NTP Result] *****************************************************************
ok: [172.16.10.14] => {
    "msg": {
        "banners": {},
        "changed": true,
        "commands": [
            "ntp server 3.3.3.3",
            "ntp server 4.4.4.4",
            "ntp server 5.5.5.5"
        ],
        "failed": false,
        "updates": [
            "ntp server 3.3.3.3",
            "ntp server 4.4.4.4",
            "ntp server 5.5.5.5"
        ]
    }
}

PLAY RECAP *****************************************************************************
172.16.10.14               : ok=2    changed=1    unreachable=0    failed=0    skipped=0

This way, you can capture and view the commands executed on the device, which helps in verifying and debugging the configuration changes made by Ansible.

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