Groups & Host Patterns

Group hierarchies, patterns, and limiting with --limit.

6 min readAnsible AutomationProvision

Group Hierarchies

Ansible groups can contain other groups using the :children suffix. This creates a hierarchy — the all group contains everything, and you create parent groups for different tiers or environments.

inventory.yml with group hierarchy


all:
  children:
    production:
      children:
        webservers:
          hosts:
            web1.prod.example.com:
            web2.prod.example.com:
        dbservers:
          hosts:
            db1.prod.example.com:
        monitoring:
          hosts:
            mon1.prod.example.com:

    staging:
      children:
        webservers:
          hosts:
            web1.staging.example.com:
        dbservers:
          hosts:
            db1.staging.example.com:

The production and staging groups both contain webservers and dbservers subgroups. This hierarchy enables environment-specific targeting.

Host Pattern Syntax

Host pattern examples


# All hosts
ansible all -m ping

# A group
ansible webservers -m ping

# A subgroup (dot notation)
ansible production.webservers -m ping

# Individual host
ansible web1.prod.example.com -m ping

# Wildcard
ansible 'web*.prod.example.com' -m ping

# Union (OR)
ansible 'webservers:dbservers' -m ping

# Intersection (AND)
ansible 'production:&webservers' -m ping

# Exclusion (NOT)
ansible 'all:!staging' -m ping

# Complex expression
ansible 'production:&webservers:!web2*' -m ping

Patterns combine groups, wildcards, and set operations. Use single quotes to prevent shell expansion of special characters.

The --limit Flag

Using --limit


# Limit to specific hosts
ansible-playbook site.yml --limit web1.prod.example.com

# Limit to a group
ansible-playbook site.yml --limit webservers

# Limit to a pattern
ansible-playbook site.yml --limit 'web*.prod.example.com'

# Multiple limits
ansible-playbook site.yml --limit webservers --limit monitoring

--limit restricts which hosts the playbook runs against, even if the playbook targets a larger group. It is essential for testing and staged rollouts.

Group Variables

Defining group variables inline


all:
  vars:
    ansible_user: deploy
    ansible_port: 22

  children:
    webservers:
      vars:
        http_port: 80
        app_root: /var/www
      hosts:
        web1.example.com:
        web2.example.com:

Group variables apply to all hosts in the group. They can be defined inline in inventory or in group_vars/ files.

Pattern Examples

Test patterns with --list-hosts

Use ansible all --list-hosts -i inventory.yml to verify which hosts a pattern matches before running playbooks.

Mark this lesson complete to store local progress and unlock a cleaner resume path the next time you visit.

Stage 4 · Provision

Dynamic Inventory & Scale