How do variables really work?

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1

I’ve read the docs, several topics in this group, the examples github, plus several experiments on some testing vms, but I can’t seem to make it click.

The precedence vars take is this: (I think…)

  1. vars passed in from the commandline
  2. vars directly in the playbook
  3. vars in host_vars/hostname
  4. vars in group_vars/group
  5. vars in roles/rolename/vars (how does this work with more than one role defining a var?)
  6. vars in group_vars/all

I also have been having issues referencing vars. I thought you could do use ${var}, {{ var }}, or $var (see: http://www.ansibleworks.com/docs/playbooks.html#vars-section), but when I do something like:

template: src=blah.j2 dest=/etc/blah/{{ var }}

It creates a file named {{ var }} rather than what the variable is supposed to be. Same if I used ${var}

I also have a task in a role that I want to run only if the host has the correct variable defined. As in host_vars/alpha.blah.org has ‘vhost’ defined, but host_vars/beta.blah.org does not. So the task would run for alpha.blah.org, but not for beta.blah.org. I tried:

  • name: blah
    template: src=blah dest=blah
    when: vhost is defined

where only host_vars/alpha.blah.org had vhost defined. The result was no tasks were run for alpha.blah.org, but the other two hosts I’m testing on had tasks run…

I guess I need these questions answered:

  1. What do I have wrong in what I wrote above?

  2. How do I correctly reference vars?

  3. How do I make sure var files are loaded correctly?

  4. As in vars for alpha.blah.org are only used for alpha.blah.org, vars for beta.blah.org are only used for beta.blah.org, and so on.1. How do I run tasks only when the correct variable is defined?

The way I’ve been testing this, is by trying to create apache vhost files. Here are what I think are the relevant files:

file: roles/webtier/tasks/main.yml

  • include: php-apache-stack.yml
  • include: apache2-vhosts.yml

file: roles/webtier/tasks/apache2-vhosts.yml

  • name: create and enable vhosts
    when: apache2_vhosts is defined
    template: src=http-vhost.j2 dest=/etc/apache2/sites-available/${item.server_name}
    with_items:
  • apache2_vhosts
    notify:
  • restart apache2

file: host_vars/vm.blankalpha.lab

testvars:

  • test1: “THis is a test with bad grammar.”
    test2: “TEST TWO”

apache2_vhosts:

  • server_name: vm.blankalpha.lab
    server_admin: webservices@blah.org
    server_aliases: done.blankalpha.lab
    docroot: /var/www/

When I did not have the when condition, it created a file named /etc/apache2/sites-available/${item.server_name} that contained my template, without any values substituted into it.

2

This feels like you may want to stop by IRC.