How do ansible host_vars work?

Question

I created a repo to reproduce my scenario.

Essentially we are loading an inventory with our hosts, we can override values per-host via the inventory without issue but would like to try and utilize host_vars.

I'm not 100% clear on how host vars are matched to the host. I read the ansible repo for examples but cannot seem to get it to work as documented so I'm looking for some scrutiny of our setup.

When I run the command ansible-playbook -i ansible.inventory site.yml -clocal in my example repo I expect the host_vars/{{ ansible_hostname }} file to be read and override anything set in the vars but that does not appear to be happening.

Can someone please point me at a working example so I can see where we are going wrong?

Answer 1

Since the documentation is not very specific on this topic here is the order of precedence for vars in the current version of Ansible (the first item has the highest precedence):

1. Vars set on the command line -e foo=set_on_cmd_line
2. Vars set in the vars_files: block in the play
3. Vars set in the vars: block in the play
4. Vars set in host_vars/
5. Vars set in group_vars/
6. Role default vars roles/.../defaults/main.yml

See Ansible docs for a more detailed list.

You should think of host_vars and group_vars more like defaults rather than overrides for defaults. If you have the same var set in you vars_files: block like you do in your example it will take precedence.