CODEWITHSUNDEEP
ansibleyamlansible-inventory
Vasiliy Sharapov
Vasiliy Sharapov

Reputation: 1057

Ansible - specify host variables for a host used in multiple groups

Is there a DRY way to specify host variables for hosts in multiple groups? e.g.:

all:
  hosts:
    mail.example.com:
      ansible_host: 10.10.10.33
  children:
    webservers:
      hosts:
        foo.example.com:
          ansible_host: 10.10.10.17
        bar.example.com:
          ansible_host: 10.10.10.18
    dbservers:
      hosts:
        one.example.com:
          ansible_host: 10.10.10.1
        two.example.com:
          ansible_host: 10.10.10.2
        three.example.com:
          ansible_host: 10.10.10.3
    test:
      hosts:
        bar.example.com:
          ansible_host: 10.10.10.18 # Don't like this being defined in a 2nd place
        three.example.com:
          ansible_host: 10.10.10.3  # =( Same

Is it possible to have host variables, like ansible_host in the example (or a SW license) defined in only one place? I wasn't able to find anything suitable in the ansible documentation, so the placeholder solution is to use YAML anchors:

all:
  hosts:
    mail.example.com:
      ansible_host: 10.10.10.33
  children:
    webservers:
      hosts:
        foo.example.com:
          ansible_host: 10.10.10.17
        bar.example.com: &bar
          ansible_host: 10.10.10.18
    dbservers:
      hosts:
        one.example.com:
          ansible_host: 10.10.10.1
        two.example.com:
          ansible_host: 10.10.10.2
        three.example.com: &three
          ansible_host: 10.10.10.3
    test:
      hosts:
        bar.example.com:
          << : *bar
        three.example.com:
          << : *three

Upvotes: 4

Views: 1243

Answers (1)

larsks
larsks

Reputation: 311238

Is it possible to have host variables, like ansible_host in the example (or a SW license) defined in only one place?

If you define variables for a host anywhere in your inventory file, those variables will be set for that host when Ansible runs. So for example, you could write your inventory like this:

all:
  hosts:
    mail.example.com:
      ansible_host: 10.10.10.33
    foo.example.com:
      ansible_host: 10.10.10.17
    bar.example.com:
      ansible_host: 10.10.10.18
    one.example.com:
      ansible_host: 10.10.10.1
    two.example.com:
      ansible_host: 10.10.10.2
    three.example.com:
      ansible_host: 10.10.10.3
  children:
    webservers:
      hosts:
        foo.example.com:
        bar.example.com:
    dbservers:
      hosts:
        one.example.com:
        two.example.com:
        three.example.com:
    test:
      hosts:
        bar.example.com:
        three.example.com:

But this would also work:

all:
  hosts:
    mail.example.com:
      ansible_host: 10.10.10.33
  children:
    webservers:
      hosts:
        foo.example.com:
          ansible_host: 10.10.10.17
        bar.example.com:
          ansible_host: 10.10.10.18
    dbservers:
      hosts:
        one.example.com:
          ansible_host: 10.10.10.1
        two.example.com:
          ansible_host: 10.10.10.2
        three.example.com:
          ansible_host: 10.10.10.3
    test:
      hosts:
        bar.example.com:
        three.example.com:

I would argue that the first version is a bit more obvious.

Upvotes: 8

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