Add a host to inventory dynamically in ansible

Question

I try to add a local KVM maschine dynamically to ansible inventory with ansible 2.11.6.

ansible [core 2.11.6]
  config file = /home/ansible/ansible.cfg
  configured module search path = ['/home/ansible/library']
  ansible python module location = /usr/local/lib/python3.9/dist-packages/ansible
  ansible collection location = /home/ansible/.ansible/collections:/usr/share/ansible/collections
  executable location = /usr/local/bin/ansible
  python version = 3.9.2 (default, Feb 28 2021, 17:03:44) [GCC 10.2.1 20210110]
  jinja version = 3.0.2
  libyaml = True

I create the KVM successful, start it, wait for port 22 and try to add it to inventory with following task in play "A":

- name: "{{libvirt_maschine_name}}: Add VM to in-memory inventory"
  local_action:
    module: add_host
    name: "{{libvirt_maschine_name}}"
    groups: libvirt
    ansible_ssh_private_key_file: "{{ansible_user_home}}/.ssh/{{libvirt_maschine_name}}-ssh.key"
    ansible_default_ipv4: "{{vm_ip}}"
    ansible_ssh_common_args: '-o StrictHostKeyChecking=no'
    ansible_host: "{{vm_ip}}"

When i output the content of hostvars in Play "B" i see the groups and hostname as expected:

...
            "group_names": [
                "libvirt"
            ],
            "groups": {
                "all": [
                    "ansible",
                    "k8smaster"
                ],
                "libvirt": [
                    "k8smaster"
                ],
                "local_ansible": [
                    "ansible"
                ],
                "ungrouped": []
            },
...

When i add

- debug: var=group_names
- debug: var=play_hosts

to my play "B", i get just the static information of my inventory.

TASK [debug] ****************************************************************************************************************************************************************************************************
ok: [ansible] => {
    "group_names": [
        "local_ansible"
    ]
}

TASK [debug] ****************************************************************************************************************************************************************************************************
ok: [ansible] => {
    "play_hosts": [
        "ansible"
    ]
}

My inventory.ini looks like

[all]
ansible ansible_host=localhost

[local_ansible]
ansible ansible_host=localhost

[local_ansible:vars]
ansible_ssh_private_key_file=~/.ssh/ansible.key
ansible_ssh_common_args='-o StrictHostKeyChecking=no'
ansible_user=ansible

Here is a minimal example:

---

- name: "Play A"
  hosts: all
  become: yes
  gather_facts: yes

  tasks:

    - name: "Import variables from file"
      include_vars:
        file: k8s-single-node_vars.yaml

    - name: "Do some basic stuff"
      include_role:
        name: ansible-core

    - name: "Add VM to in-memory inventory"
      add_host:
        name: "myMaschine"
        groups: myGroup
        ansible_ssh_private_key_file: "test.key"
        ansible_default_ipv4: "192.168.1.1"
        ansible_ssh_common_args: '-o StrictHostKeyChecking=no'
        ansible_host: "192.168.1.1"

- name: "Play B"
  hosts: all
  become: yes
  gather_facts: no
  tasks:

    - debug: var=hostvars
    - debug: var=group_names
    - debug: var=play_hosts

    - name: test-ping
      ping:

Therefore, i am not able to run any task against the VM, because ansible is completely ignoring them. A ping is just working against the host "ansible". Any idea, what i do wrong here?

Without knowing what the hosts: looks like for "play B" it's hard to help you. Please read the how to ask page, and pay especial attention to the MCVE section — mdaniel
– mdaniel, Commented Oct 20, 2021 at 4:40

Vladimir Botka · Accepted Answer · 2021-10-20 06:51:45Z

0

Minimal inventory and minimal playbook show that everything works as expected with Python 3.8.

You are running ansible with Python 3.9 Try to downgrade.

shell> ansible --version
ansible [core 2.11.5]
...
python version = 3.8.5 (default, Jan 27 2021, 15:41:15) [GCC 9.3.0]
jinja version = 3.0.1

shell> cat inventory.ini
localhost

shell> cat playbook.yml
---
- name: Play A
  hosts: all
  gather_facts: false
  tasks:
    - add_host:
        name: myMaschine
        groups: myGroup

- name: Play B
  hosts: all
  gather_facts: false
  tasks:
    - debug:
        var: group_names
    - debug:
        var: ansible_play_batch

shell> ansible-playbook -i inventory.ini playbook.yml

PLAY [Play A] ***************************************

TASK [add_host] *************************************
changed: [localhost]

PLAY [Play B] ***************************************

TASK [debug] ****************************************
ok: [myMaschine] =>
  group_names:
  - myGroup
ok: [localhost] =>
  group_names:
  - ungrouped

TASK [debug] ****************************************
ok: [myMaschine] =>
  ansible_play_batch:
  - myMaschine
  - localhost
ok: [localhost] =>
  ansible_play_batch:
  - myMaschine
  - localhost

PLAY RECAP ******************************************
localhost:  ok=3 changed=1 unreachable=0 failed=0 ...
myMaschine: ok=2 changed=0 unreachable=0 failed=0 ...

The special variable play_hosts is deprecated but is still working, i.e. this is not the reason for the problem.

edited Oct 20, 2021 at 6:51

answered Oct 20, 2021 at 6:26

Vladimir Botka

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1 Comment

David Koenig Over a year ago

Thanks for the tip. But thats not the reason. I downgraded to python 3.8.12 and have the exact same behavior.

David Koenig · Accepted Answer · 2021-10-20 11:53:47Z

0

Found the solution. I used the limit option to limit the execution to the localhost. Since last week i used an old version of ansible which used the additional host i add dynamically. With the current version of Ansible it is needed to add the new hosts to the limit option. With "--limit ansible,libvirt" it works (when the new hosts are part of the libvirt group).

answered Oct 20, 2021 at 11:53

David Koenig

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