Ansible 15. template in ansible

1️⃣ What is an Ansible Template?

In Ansible, a template is a file (usually with .j2 extension, meaning Jinja2 template) that contains dynamic content. You can define placeholders or variables in the file, and when Ansible runs, it replaces these placeholders with actual values from your variables, host facts, or inventory.

• Template file → usually in templates/ folder in your Ansible project

• Module used → ansible.builtin.template

• Purpose → To generate configuration files dynamically based on variables.

Example placeholder in template:

# db_config.conf.j2
db_name={{ db_name }}
db_user={{ db_user }}
db_password={{ db_password }}

2️⃣ How It Works

Suppose you want to create a database configuration file for Oracle. Instead of writing separate files for each database, you can use a template:

• Template contains variables: {{ db_name }}, {{ db_user }}, etc.

• Playbook provides values for these variables.

• Template module copies the rendered file to the target server.

Scenario:
You want to create an init.ora (Oracle initialization parameter file) for multiple Oracle databases dynamically using Ansible.

---

Step 1: Create a template file

templates/init.ora.j2

# Oracle Initialization Parameter File
db_name={{ db_name }}
memory_target={{ memory_target }}
processes={{ processes }}
audit_file_dest={{ audit_file_dest }}

---

Step 2: Create a playbook

create_oracle_init.yml

---
- name: Deploy Oracle init.ora files
  hosts: oracle_servers
  become: yes
  vars:
    databases:
      - name: PRODDB
        memory_target: 2G
        processes: 300
        audit_file_dest: /u01/app/oracle/admin/PRODDB/adump
      - name: TESTDB
        memory_target: 1G
        processes: 150
        audit_file_dest: /u01/app/oracle/admin/TESTDB/adump

  tasks:
    - name: Generate init.ora from template
      ansible.builtin.template:
        src: init.ora.j2
        dest: "/u01/app/oracle/admin/{{ item.name }}/init.ora"
        owner: oracle
        group: oinstall
        mode: 0644
      loop: "{{ databases }}"
      loop_control:
        label: "{{ item.name }}"

---

Step 3: What happens when you run this playbook

• For PRODDB, the template will create:

db_name=PRODDB
memory_target=2G
processes=300
audit_file_dest=/u01/app/oracle/admin/PRODDB/adump

• For TESTDB, it will create:

db_name=TESTDB
memory_target=1G
processes=150
audit_file_dest=/u01/app/oracle/admin/TESTDB/adump

✅ No need to manually edit files for each database.

---

4️⃣ Why this is useful

• Automates repetitive tasks for multiple databases.

• Ensures consistency across environments (dev, test, prod).

• Variables can come from inventory, host facts, or external files.

• Reduces human errors when configuring multiple Oracle databases.