Ansible regex to replace the DNS address in Ubuntu netplan file

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I would like to change DNS IP address from 192.168.86.14 to 192.168.86.16 in Ubuntu netplan yaml file:

      link: ens3
      addresses: [192.168.86.12/24]
      gateway4: 192.168.86.1
      nameservers:
        addresses: [192.168.86.14,8.8.8.8,8.8.4.4]

Here is my ansible playbook:

 - name: test
    ansible.builtin.replace:
      path: /etc/netplan/00-installer-config.yaml
      regexp: '(addresses: \[)+192.168.86.14,'
      replace: '\1192.168.86.16,'

My playbook doesn't change anything in the file. Tried to escape comma but doesn't match anything as well.

For some reason I need to make sure the IP address is between "addresses [" and "," so I can't just use the syntax like this :

 - name: test
    ansible.builtin.replace:
      path: /etc/netplan/00-installer-config.yaml
      regexp: '192.168.86.14'
      replace: '192.168.86.16'

I am very new to Ansible, any help is appreciated!

ansible ubuntu regex
1 Answers

The dictionaries are immutable in YAML. But, you can update dictionaries in Jinja2. Let's take a complete example of a netplan configuration file, e.g.

shell> cat 00-installer-config.yaml
network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      mtu: 9000
    enp3s0:
      link: ens3
      addresses: [192.168.86.12/24]
      gateway4: 192.168.86.1
      nameservers:
        addresses: [192.168.86.14,8.8.8.8,8.8.4.4]

Read the dictionary into a variable

    - include_vars:
        file: 00-installer-config.yaml
        name: netplan_conf

gives

  netplan_conf:
    network:
      ethernets:
        enp3s0:
          addresses:
          - 192.168.86.12/24
          gateway4: 192.168.86.1
          link: ens3
          nameservers:
            addresses:
            - 192.168.86.14
            - 8.8.8.8
            - 8.8.4.4
        ens3:
          mtu: 9000
      renderer: networkd
      version: 2

Create a template that updates the nameservers

shell> cat 00-installer-config.yaml.j2
{% set _dummy = netplan_conf.network.ethernets.enp3s0.nameservers.update({'addresses': _addresses}) %}
{{ netplan_conf|to_nice_yaml }}

The task below

    - template:
        src: 00-installer-config.yaml.j2
        dest: 00-installer-config.yaml
      vars:
        _addresses: "{{ netplan_conf.network.ethernets.enp3s0.nameservers.addresses|
                        regex_replace('192.168.86.14', '192.168.86.16') }}"

will update the configuration file

shell> cat 00-installer-config.yaml
network:
    ethernets:
        enp3s0:
            addresses:
            - 192.168.86.12/24
            gateway4: 192.168.86.1
            link: ens3
            nameservers:
                addresses:
                - 192.168.86.16
                - 8.8.8.8
                - 8.8.4.4
        ens3:
            mtu: 9000
    renderer: networkd
    version: 2
user_64825610
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