Variable precedence: inventory versus host_vars

[candlerb]

Something which is very unclear at either

http://www.ansibleworks.com/docs/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable

or

http://www.ansibleworks.com/docs/intro_inventory.html#splitting-out-host-and-group-specific-data

is the precedence between

host_vars/<hostname>   # yaml format

and direct entries in the inventory file (<hostname> <var1>=<val1> <var2>=<val2>)

Some experimentation has shown that a variable set in the inventory file appears to take precedence over host_vars.

Is this guaranteed? Have I missed some documentation?

Thanks,

Brian.

[Michael DeHaan]

Specifically what sentence or statement is unclear?  I'd be happy to clarify

As for "Some experimentation has shown that a variable set in the inventory file appears to take precedence over host_vars."

These are equivalent ways to set inventory variables.   

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Michael DeHaan <mic...@ansibleworks.com>
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[candlerb]

On Sunday, 20 October 2013 02:19:16 UTC+1, Michael DeHaan wrote:

Specifically what sentence or statement is unclear?  I'd be happy to clarify

As for "Some experimentation has shown that a variable set in the inventory file appears to take precedence over host_vars."

These are equivalent ways to set inventory variables.   

OK, so what I mean is: if you set an inventory variable in the hosts file and in host_vars, which takes precedence, and can I depend on this?

The reason: I want to distribute some re-usable configs (these are virtual lab setups) to multiple users. I want to put the "normal" configs somewhere, and also have a single place where the user can override them. e.g.

host_vars/s1

lan_address: 10.10.0.241

So everyone who builds the lab will have normally have s1's lan address as 10.10.0.241. But if they want to, they can edit the hosts file as an override:

s1 ansible_connection=local lan_address=1.2.3.4

Regards,

Brian.

[Michael DeHaan]

"if you set an inventory variable in the hosts file and in host_vars, which takes precedence, and can I depend on this?"

No, you can't.

Best practices would suggest putting variables *only* in host_vars/group_vars, unless it's something like an ansible_ control variable, where having that in inventory can be convient.

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[Jeremy Schulman]

Hi,

I ran across this same "not issue" thinking that my host_vars/x.yml would override the inventory file.  I get the Ansible Zen approach, and now that I know the answer from MD above, I am A-OK.  I think it would be *nice* if this information was covered in the Ansible docs specifically so folks can easy access to this answer.

Thank you.
-- Jeremy

[Azul Inho]

I had similar doubts last week, got my answers on the irc channel.

Quick question for Michael, do you use git for your documentation pages or is it wiki based? I would be happy to submit a pull request with enhancements to the docs.
It would also help me with my bad memory

[Brian Coca]

docs are inside same git repo as the rest of ansible, PRs for docs work just like PRs to code.