how to run a particular task on specific host in ansible

Question

my inventory file\'s contents -

[webservers]
x.x.x.x ansible_ssh_user=ubuntu

[dbservers]
x.x.x.x ansible_ssh_user=ubuntu

in my tasks file

Answer 1

If you want to run your role on all hosts but only a single task limited to the webservers group, then - like you already suggested - when is your friend.

You could define a condition like:

when: inventory_hostname in groups['webservers']

Answer 2

Thank you, this helps me too.

hosts file:

[production]
host1.dns.name

[internal]
host2.dns.name

requirements.yml file:

- name: install the sphinx-search rpm from a remote repo on x86_64 - internal host
  when: inventory_hostname in groups['internal']
  yum:
    name: http://sphinxsearch.com/files/sphinx-2.2.11-1.rhel7.x86_64.rpm
    state: present

- name: install the sphinx-search rpm from a remote repo on i386 - Production
  when: inventory_hostname in groups['production']
  yum:
    name: http://sphinxsearch.com/files/sphinx-2.2.11-2.rhel6.i386.rpm
    state: present

Answer 3

An alternative to consider in some scenarios is -

delegate_to: hostname

There is also this example form the ansible docs, to loop over a group. https://docs.ansible.com/ansible/latest/user_guide/playbooks_delegation.html -

- hosts: app_servers

  tasks:
    - name: gather facts from db servers
      setup:
      delegate_to: "{{item}}"
      delegate_facts: True
      loop: "{{groups['dbservers']}}"