How to make Ansible run one certain task only on one host?

Question

The playbook looks like:

- hosts: all
  tasks:
    - name: "run on all hosts,1"
      shell: something1
    - name: "run on all hosts,2"
      shell: something2
    - name: "run on one host, any host would do"
      shell: this_command_should_run_on_one_host
    - name: "run on all hosts,3"
      shell: something3

I know with command line option --limit, I can limit to one host, is it possible to do it in playbook?

question from:https://stackoverflow.com/questions/47342724/how-to-make-ansible-run-one-certain-task-only-on-one-host

Answer 1

For any host (with defaults it will match the first on the list):

- name: "run on first found host"
  shell: this_command_should_run_on_one_host
  run_once: true

For a specific host:

- name: "run on that_one_host host"
  shell: this_command_should_run_on_one_host
  when: ansible_hostname == 'that_one_host'

Or inventory_hostname (hostname as defined in the Ansible inventory) instead of ansible_hostname (hostname as defined on the target machine), depending on which name you want to use.