Interview › Infrastructure as Code (Terraform, Ansible)
What are group_vars and host_vars?
Infrastructure as Code (Terraform, Ansible) · Intermediate level
Answer
group_vars define variables for a group of hosts, while host_vars define variables for a single host. They let the same playbook adapt to environments, regions, roles, or individual host differences without embedding conditionals everywhere.
Technical explanation
group_vars/all applies broadly; group-specific files apply to that group; host_vars applies to one host.
Variables can be organized as directories with multiple files for readability.
Use inventory hierarchy carefully when a host belongs to multiple groups.
Prefer idempotent modules over shell so repeated runs are safe and change reporting is meaningful.
Separate reusable role logic from inventory-specific variables so the same automation works across environments.
Run lint, syntax checks, check mode where useful, and staged rollouts before production-wide changes.
Hands-on example
1. Model variables and facts for: What are group_vars and host_vars?
2. Create inventory variables:
group_vars/web.yml:
app_port: 8080
package_name_by_os:
RedHat: httpd
Debian: apache2
host_vars/web1.yml:
app_port: 9090
3. Use facts and variables in a task:
- name: Install OS-specific web package
ansible.builtin.package:
name: "{{ package_name_by_os[ansible_facts['os_family']] }}"
state: present
when: ansible_facts['os_family'] in package_name_by_os
4. Run ansible-playbook site.yml -e app_port=7070 in a lab to see extra vars override lower-precedence values.
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