Accessing host variables in tasks in Ansible

问题

I have a host group which have host variables as shown below

[test:children]
test1
test2
test3

[test:vars]
clean_images=true

I have a tasks defined in a role as shown below

- name: clean docker images
  template:
    dest: "/etc/systemd/system/{{ item.name }}"
  with_items:
  - { name: "{{ service_name }}.service" }



- name: start service
  systemd:
    name: "{{ service_name }}.service"
    state: started
    enabled: yes
  when: hostvars['test'].clean_images is defined

This is a simple tasks, where I clean docker images depending on the host. I have a playbook which executes this above role in a different set of host group [test_services]. I want the task - name: start service to run if it come across any of the host groups defined in [test:children]. To check that I have added a variable clean_images=true to the test group to execute a condition check

But the when statement I have included above gives me an error

fatal: [xx.xx.xx.xx]: FAILED! => {"msg": "The conditional check 'hostvars['test'].clean_images is defined' failed. The error was: error while evaluating conditional (hostvars['test'].clean_images is defined): \"hostvars['test']\" is undefined\n\nThe error appears to have been in 'main.yml'

I have a problem in building up this conditional statement using when, any help would be great.

回答1:

when: hostvars['test'].clean_images is defined

should be just:

when: clean_images is defined and clean_images

because there is no host named test, and thus hostvars of test will never exist. All hosts that belong to the test group will have clean_images defined, however

来源：https://stackoverflow.com/questions/53718577/accessing-host-variables-in-tasks-in-ansible