Templating in Ansible allows dynamic expressions and access to variables. It is used in tasks, defaults/variables files, and templates to generate configuration files or other text-based formats. Templating occurs before tasks are executed using the Jinja2 templating language which supports tags, flow control, filters and more. Examples demonstrate templating tasks, variables files, and templates to dynamically generate configuration files using variables and expressions.

1. Templating in Ansible
Jiri Tyr

2. About me
● Using Ansible for 3+ years
● Ansible contributor
○ Modules: yum_repository, jenkins_plugin, ldap_attr, ldap_entry
○ Jinja2 filter: comment
○ Bug fixing (mount module)
○ Code reviews
● Author of nearly 100 public Ansible roles
○ https://github.com/jtyr
○ https://galaxy.ansible.com/jtyr

3. What is Ansible templating?

4. What is templating
● Allows dynamic expressions and access to variables
● Used in
○ Tasks
○ Defaults/Variables
○ Templates
● Happens before the task is sent for execution to target machine
● Using Jinja2 language

5. Jinja2 language
● Modern and designer-friendly templating language for Python
● Heavily inspired by Django and Python
● Generates any text-based format
● Consists of tags
○ {% %} - statement
○ {{ }} - expression
○ {# #} - comment
● Tags can contain
○ Flow controls
■ if / else
■ for
○ Filters
○ ...

6. Templating tasks

7. Example - tasks
---
- hosts: all
tasks:
- template:
src: myfile.cfg .j2
dest: /etc/myfile.cfg
owner: root
group: root
mode: 0644
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

8. Example - tasks
---
- hosts: all
vars:
filename: /etc/myfile.cfg
owner: root
group: root
mode: 0644
tasks:
- template:
src: myfile.cfg.j2
dest: " {{ filename }}"
owner: "{{ owner }}"
group: "{{ group }}"
mode: "{{ mode }}"
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

9. Example - tasks
---
- hosts: all
vars:
filename: /etc/myfile.cfg
owner: root
group: root
mode: "{{ 0644 if owner == 'root' else 0640 }}"
tasks:
- template:
src: myfile.cfg.j2
dest: "{{ filename }}"
owner: "{{ owner }}"
group: "{{ group }}"
mode: "{{ mode }}"
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

10. Templating defaults/variables file

11. Example - defaults/variables file
---
myfile_config_section1_option11 : value11
myfile_config_section1_option12 : value12
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

12. Example - defaults/variables file
---
myfile_config:
section1:
option11: value11
option12: value12
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

13. Example - defaults/variables file
---
myfile_section1_option11 : value11
myfile_section1_option12 : value12
myfile_config:
section1:
option11: "{{ myfile_section1_option11 }}"
option12: "{{ myfile_section1_option12 }}"
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

14. Example - defaults/variables file
---
myfile_section1_option11 : value11
myfile_section1_option12 : value12
myfile_option11 :
option11: "{{ myfile_section1_option11 }}"
myfile_option12 :
option12: "{{ myfile_section1_option12 }}"
myfile_section1 : "{{
myfile_option11 .update(myfile_option12 ) }}{{
myfile_option11 }}"
myfile_config:
section1: "{{ myfile_section1 }}"
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

15. Example - defaults/variables file
---
myfile_section1_option11: value11
myfile_section1_option12: value12
myfile_section1__default:
option11: "{{ myfile_section1_option11 }}"
option12: "{{ myfile_section1_option12 }}"
myfile_section1__custom: []
myfile_section1: "{{
myfile_section1__default.update(myfile_section1__custom)}}{{
myfile_section1__default}}"
myfile_config__default:
section1: "{{ myfile_section1 }}"
myfile_config__custom: {}
myfile_config: "{{
myfile_config__default.update(myfile_config__custom) }}{{
myfile_config__default }}"
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

16. Templating dict key

17. Example - templating dict keys
---
myfile_section1_name : section1
myfile_config:
"{{ myfile_section1_name }}":
option11: value11
option12: value12
# /etc/myfile.cfg
[{{ myfile_section1_name }} ]
option11=value11
option12=value12

18. Example - templating dict keys
---
myfile_section1_name : section1
myfile_config: "{
'{{ myfile_section1_name }}': {
'option11': 'value11',
'option12': 'value12'
}
}"
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12
Inline YAML format with quoted keys and values.

19. ---
myfile_section1_name: section1
myfile_section1_option11_name: option11
myfile_section1_option12_name: option12
myfile_section1_option11_value: value11
myfile_section1_option12_value: value12
myfile_section1: "{
'{{ myfile_section1_option11_name }}': '{{ myfile_section1_option11_value }}',
'{{ myfile_section1_option11_name }}': '{{ myfile_section1_option11_value }}'
}"
myfile_config: "{
'{{ myfile_section1_name }}': {{ myfile_section1 }}
}"
Example - templating dict keys
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

20. Templating templates file

21. Example - templates file
[section1]
option11={{ myfile_config_section1_option11 }}
option12={{ myfile_config_section1_option12 }}
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

22. Example - templates file
{% for sect, opts in myfile_config.iteritems() %}
{# This is the section #}
[{{ sect }}]
{% for opt, val in opts.iteritems() %}
{# This is the key-value #}
{{ opt }}={{ val }}
{% endfor %}
{% endfor %}
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

23. Example - templates file
{% for sect, opts in myfile_config.iteritems() %}
{# This is the section #}
[{{ sect }}]
{% for opt, val in opts.iteritems() %}
{# This is the key-value #}
{{ opt }}={{ val }}
{% endfor %}
{% endfor %}
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

24. Example - templates file
{% for sect, opts in myfile_config.iteritems() %}
{# This is the section #}
{# #}[{{ sect }}]
{% for opt, val in opts.iteritems() %}
{# This is the key-value #}
{# #}{{ opt }}={{ val }}
{% endfor %}
{% endfor %}
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12

25. Example - templates file
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12
{% for sect, opts in myfile_config.iteritems() %}
{#- This is the section -#}
[{{ sect }}]{{ "n" }}
{%- for opt, val in opts.iteritems() %}
{#- This is the key-value -#}
{{ opt }}={{ val }}{{ "n" }}
{%- endfor %}
{% endfor %}

26. Example - templates file
# /etc/myfile.cfg
[section1]
option11=value11
option12=value12
{% for sect, opts in myfile_config.iteritems() %}
{#- This is the section -#}
[{{ sect }}]{{ "n" }}
{%- for opt, val in opts.iteritems() %}
{#- This is the key-value -#}
{{ opt ~ "=" ~ val ~ "n" }}
{%- endfor %}
{% endfor %}

27. Example - templates file
# /etc/myfile.cfg
[section1]
OPTION11 = value11
OPTION12 = value12
{% for sect, opts in myfile_config.iteritems() %}
{#- This is the section -#}
[{{ sect }}]{{ "n" }}
{%- for opt, val in opts.iteritems() %}
{#- This is the key-value -#}
{{ opt | upper ~ myfile_config_sep ~ val ~ "n" }}
{%- endfor %}
{% endfor %}

28. Thank you for your attention!
Questions?