Ansible - Default/Explicit Tags

Question

I've got a playbook that includes and tags various roles:

- name:  base
  hosts: "{{ host | default('localhost') }}"

roles: 

  - { role: apt,              tags: [ 'base', 'apt', 'ubuntu']}
  - { role: homebrew,         tags: [ 'base', 'homebrew', osx' ]}
  - { role: base16,           tags: [ 'base', 'base16', 'osx' ]}
  - { role: nodejs,           tags: [ 'base', 'nodejs' ]}
  - { role: tmux,             tags: [ 'base', 'tmux' ]}
  - { role: vim,              tags: [ 'base', 'vim' ]}
  - { role: virtualenv,       tags: [ 'base',  virtualenv', 'python' ]}
  - { role: homebrew_cask,    tags: [ 'desktop', 'homebrew_cask', osx' ]}
  - { role: gnome_terminator, tags: [ 'desktop', 'gnome_terminator', ubuntu' ]}

Most of the tasks are using when clauses to determine which OS they should run on, for example:

- name: install base packages
  when: ansible_distribution == 'MacOSX'
  sudo: no
  homebrew:
    name: "{{ item.name }}"
    state: latest
    install_options: "{{ item.install_options|default() }}"
  with_items: homebrew_packages

If I run ansible-playbook base.yml without specifying any tags, all the tasks run. If I specify a tag, for example ansible-playbook base.yml --tags='base', only the roles tagged with base run.

By default (if no tags are specified), I'd only like to run the roles tagged with 'base', and not the roles tagged with 'desktop'.

It would also be really nice to set a default 'os' tag, based on the current operating system, to avoid including all the tasks for the ubuntu when I'm running the playbook on OSX (and vice-versa).

Any ideas if this is possible, and how I might do it?

Answer 1

Since Ansible 2.5 there is a new feature which solves these kinds of situations.

Another special tag is never, which will prevent a task from running unless a tag is specifically requested.

Example:

tasks:
  - debug: msg='{{ showmevar}}'
    tags: [ 'never', 'debug' ]

So your problem should be addressed like this:

- name:  base
  hosts: "{{ host | default('localhost') }}"

roles: 

  - { role: apt,              tags: [ 'base', 'apt', 'ubuntu']}
  - { role: homebrew,         tags: [ 'base', 'homebrew', osx' ]}
  - { role: base16,           tags: [ 'base', 'base16', 'osx' ]}
  - { role: nodejs,           tags: [ 'base', 'nodejs' ]}
  - { role: tmux,             tags: [ 'base', 'tmux' ]}
  - { role: vim,              tags: [ 'base', 'vim' ]}
  - { role: virtualenv,       tags: [ 'base',  virtualenv', 'python' ]}
  - { role: homebrew_cask,    tags: [ 'never','desktop', 'homebrew_cask', osx' ]}
  - { role: gnome_terminator, tags: [ 'never','desktop', 'gnome_terminator', ubuntu' ]}

Answer 2

Unfortunately there is no such feature. Tag handling in Ansible currently is very limited. You can not set default tags and you can not exclude tags by default.

There are some threads on the Google user group and feature requests on github regarding this. But no outcome yet. The common answer so far is, you should create a shell script and place it in front of your playbook. This script then can set the --tags and --skip-tags accordingly to your needs. Very unpleasant but as far as I know the only option right now.