# Merge/Combine Inventory Variables with Defaults rather than override **URL:** \ **Category:** Ansible Project\ **Created:** [June 4, 2018, 1:37pm UTC](https://forum.ansible.com/t/merge-combine-inventory-variables-with-defaults-rather-than-override/27701 "2018-06-04T13:37:39Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![christoph.vogelsberg](https://avatars.discourse-cdn.com/v4/letter/c/2acd7d/32.png) [@christoph.vogelsberg](https://forum.ansible.com/u/christoph.vogelsberg)\ **Post date:** [June 4, 2018, 1:37pm UTC](https://forum.ansible.com/t/merge-combine-inventory-variables-with-defaults-rather-than-override/27701/1 "2018-06-04T13:37:39Z")
Hey folks, the `defaults/main.yml` in a Role will be overridden in the precedence chain. In essence, as I understand, it is a dictionary that will be overlayed/merged/combined with sub-sequent variable settings (e.g. by inventory variables) [in the manner as described here](https://docs.ansible.com/ansible/latest/user_guide/playbooks_filters.html#combining-hashes-dictionaries). But I suspect, this isn’t done recursively. _How can I achieve recursive combination of dictionaries in the defaults?_ I discovered that many definitions are flat, e.g. `myapp_component1_feature1: defaultA myapp_component1_feature2: defaultB myapp_component2_feature1: defaultC myapp_component2_feature2: defaultD` instead of `myapp: component1: feature1: defaultA feature2: defaultB component2: feature1: defaultC feature2: defaultD` The second schema is favorable not only for elegance but also if e.g. I would like to iterate over components of myapp or over features of a component with Jinja. However, when I want to use the defaults in e.g. an inventory file in a suggestive manner ` [www.example.com](http://www.example.com) vars: myapp: component1: feature2: myvalueB component2: feature1: myvalueC ` The sub-dictionaries will be overridden instead of being combined. It will only contain the explicit elements. ---
**Author:** ![Kai\_Stian\_Olstad](https://avatars.discourse-cdn.com/v4/letter/k/e19adc/32.png) [@Kai\_Stian\_Olstad](https://forum.ansible.com/u/Kai_Stian_Olstad)\ **Post date:** [June 6, 2018, 10:01am UTC](https://forum.ansible.com/t/merge-combine-inventory-variables-with-defaults-rather-than-override/27701/2 "2018-06-06T10:01:21Z")
That link to is a filter that you can use in your code to combine hashes/dictonaries and has nothing to on how Ansible overwrite/replace variables. Default Ansible overwrite the whole variables in a predetermine order, variable precedence, that is documented here [http://docs.ansible.com/ansible/latest/user\_guide/playbooks\_variables.html#variable-precedence-where-should-i-put-a-variable](http://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#variable-precedence-where-should-i-put-a-variable) Ansible has an option hash\_behavior(default is replace) that you can set to merge, it will then merge hashes/dictonaries instead of replacing them. ---
**Author:** ![christoph.vogelsberg](https://avatars.discourse-cdn.com/v4/letter/c/2acd7d/32.png) [@christoph.vogelsberg](https://forum.ansible.com/u/christoph.vogelsberg)\ **Post date:** [June 6, 2018, 2:00pm UTC](https://forum.ansible.com/t/merge-combine-inventory-variables-with-defaults-rather-than-override/27701/3 "2018-06-06T14:00:46Z")
Hi Kai, > Ansible has an option hash\_behavior(default is replace) that you can set > to merge, it will then merge hashes/dictonaries instead of replacing > them. Unfortunately, [DEFAULT\_HASH\_BEHAVIOUR (Ansible Docs)](http://docs.ansible.com/ansible/latest/reference_appendices/config.html?highlight=hash_behaviour#default-hash-behaviour) states that it is not a recommended practice. But luckely, I found a way that seems to be pretty straight-forward: role/default/main.yml ` `myapp_defaults: component1: feature1: defaultA feature2: defaultB component2: feature1: defaultC feature2: defaultD` ` role/vars/main.yml ` myapp\_vars: | {%- if myapp is defined and myapp is iterable -%} {{ myapp\_defaults | combine (myapp, recursive=True) }} {%- else -%} {{ myapp\_defaults }} {%- endif -%} ` The usage in the role/tasks/xyz.yml then is e.g. ` - name: Some task XXX: YYY: “{{ myapp\_vars.component2.feature1 }}” … … ` Applying the role e.g. with play vars ` # My Playbook - name: setup MyApp vars: myapp: component2: feature1: “foo” feature2: “bar” tasks: - include\_role: name: myapp ` Variable precedence is important, e.g. the following wouldn’t work: ` # My Playbook - name: setup MyApp tasks: - include\_role: name: myapp vars: myapp: component2: … … ` since role/vars/main.yml is already read in when include\_vars are applied. ---
**Author:** ![Max\_Bigras](https://avatars.discourse-cdn.com/v4/letter/m/f07891/32.png) [@Max\_Bigras](https://forum.ansible.com/u/Max_Bigras)\ **Post date:** [May 4, 2019, 9:04am UTC](https://forum.ansible.com/t/merge-combine-inventory-variables-with-defaults-rather-than-override/27701/4 "2019-05-04T09:04:17Z")
Hi christoph, Was very excited to see your solution to this problem. I’ve been struggling to find a way to work around ansible replacing dictionaries. Are you still using this approach? How has it been working for you? Have you made any changes? ---
**Author:** ![Aravinda\_R](https://avatars.discourse-cdn.com/v4/letter/a/bbe5ce/32.png) [@Aravinda\_R](https://forum.ansible.com/u/Aravinda_R)\ **Post date:** [April 8, 2021, 10:59am UTC](https://forum.ansible.com/t/merge-combine-inventory-variables-with-defaults-rather-than-override/27701/5 "2021-04-08T10:59:36Z")
Hi Christoph, I tried this with one of my Ansible work, looks like it does not work well if we have a nested dict. any suggestions ?