Use run_once to run a task on a single host

Short answer

Use run_once so Ansible prints a cluster-wide message once instead of on every host.

Request

print a cluster-wide message once with run_once and delegate_facts false

Example

A quick heads-up: Every environment is different. Review and test this example before you run it on systems you care about.

---
- name: Print a cluster-wide message once with run_once and delegate_facts false
  hosts: all
  gather_facts: false
  tasks:
    - name: Print cluster-wide message
      ansible.builtin.debug:
        msg: "This is a cluster-wide message"
      run_once: true
      delegate_facts: false

How it works

run_once executes the task on the first host in the current batch by default. Use it for cluster-wide setup, locking, or messages that must not repeat per host.

When to use it

• Creating a shared lock or marker once per play
• Printing a summary that should appear a single time

Requirements

• Ansible: >=2.14

Validation

• Syntax validated
• Not execution-tested
• Last verified 2026-09-09