Ansible Inventory Guide — Static, Dynamic, and Advanced Patterns

# inventory.ini
[webservers]
web1.example.com
web2.example.com
web3.example.com

[dbservers]
db1.example.com
db2.example.com

[loadbalancers]
lb1.example.com ansible_host=192.168.1.10

# Group of groups
[production:children]
webservers
dbservers
loadbalancers

# Group variables
[webservers:vars]
http_port=80
ansible_user=deploy

# inventory.yml
all:
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
        web3.example.com:
      vars:
        http_port: 80
        ansible_user: deploy

    dbservers:
      hosts:
        db1.example.com:
          postgresql_port: 5432
        db2.example.com:
          postgresql_port: 5433

    loadbalancers:
      hosts:
        lb1.example.com:
          ansible_host: 192.168.1.10

    production:
      children:
        webservers:
        dbservers:
        loadbalancers:

all:
  hosts:
    web1.example.com:
      ansible_host: 192.168.1.101
      ansible_port: 2222
      ansible_user: admin
      ansible_python_interpreter: /usr/bin/python3

inventory/
├── hosts.yml
├── group_vars/
│   ├── all.yml           # Applied to all hosts
│   ├── webservers.yml    # Applied to webservers group
│   └── production.yml    # Applied to production group
└── host_vars/
    ├── web1.example.com.yml
    └── db1.example.com.yml

# group_vars/webservers.yml
http_port: 80
ssl_cert_path: /etc/ssl/certs/site.pem
max_connections: 1000
deploy_user: www-data

# host_vars/db1.example.com.yml
postgresql_version: "16"
postgresql_max_connections: 200
backup_schedule: "0 2 * * *"

1. command line -e (highest)
2. host_vars/hostname.yml
3. group_vars/child_group.yml
4. group_vars/parent_group.yml
5. group_vars/all.yml (lowest)

# All hosts
ansible all -m ping

# Specific group
ansible webservers -m ping

# Single host
ansible web1.example.com -m ping

# Multiple groups (union)
ansible 'webservers:dbservers' -m ping

# Intersection
ansible 'webservers:&production' -m ping

# Exclusion
ansible 'all:!loadbalancers' -m ping

# Wildcard
ansible 'web*' -m ping

# Regex
ansible '~web[0-9]+\.example\.com' -m ping

# Numeric range
ansible 'web[1:3].example.com' -m ping
# Matches web1, web2, web3

# Limit at runtime
ansible-playbook site.yml --limit web1.example.com
ansible-playbook site.yml --limit 'webservers:!web3.example.com'

# aws_ec2.yml
plugin: amazon.aws.aws_ec2
regions:
  - us-east-1
  - eu-west-1

filters:
  tag:Environment:
    - production
  instance-state-name: running

keyed_groups:
  - key: tags.Role
    prefix: role
  - key: placement.region
    prefix: region
  - key: instance_type
    prefix: type

compose:
  ansible_host: public_ip_address
  instance_name: tags.Name

# Use dynamic inventory
ansible-inventory -i aws_ec2.yml --graph
ansible-playbook -i aws_ec2.yml site.yml

# azure_rm.yml
plugin: azure.azcollection.azure_rm
auth_source: auto
include_vm_resource_groups:
  - production-rg
  - staging-rg

keyed_groups:
  - prefix: tag
    key: tags

# gcp_compute.yml
plugin: google.cloud.gcp_compute
projects:
  - my-project-id
zones:
  - us-central1-a
filters:
  - status = RUNNING

keyed_groups:
  - key: labels.env
    prefix: env

# snow_inventory.yml
plugin: servicenow.itsm.now
table: cmdb_ci_linux_server
query:
  - operational_status: = operational
compose:
  ansible_host: ip_address

# Use multiple inventory files
ansible-playbook -i inventory/production -i inventory/staging site.yml

# Or use a directory
ansible-playbook -i inventory/ site.yml

# ansible.cfg
[defaults]
inventory = inventory/production,inventory/cloud

inventory/
├── production/
│   ├── hosts.yml
│   ├── group_vars/
│   │   └── all.yml
│   └── host_vars/
├── staging/
│   ├── hosts.yml
│   ├── group_vars/
│   │   └── all.yml
│   └── host_vars/
└── development/
    ├── hosts.yml
    └── group_vars/
        └── all.yml

# Deploy to staging
ansible-playbook -i inventory/staging site.yml

# Deploy to production
ansible-playbook -i inventory/production site.yml

# Combine static and dynamic
# inventory/combined.yml
plugin: ansible.builtin.constructed
strict: false
groups:
  webservers: "'web' in inventory_hostname"
  large_instances: "ansible_memtotal_mb > 16000"
compose:
  ansible_connection: "'local' if inventory_hostname == 'localhost' else 'ssh'"

# List all hosts
ansible-inventory -i inventory.yml --list

# Show graph
ansible-inventory -i inventory.yml --graph

# Show specific host variables
ansible-inventory -i inventory.yml --host web1.example.com

# Verify connectivity
ansible all -i inventory.yml -m ping

# ✅ Use YAML format
# ✅ Use group_vars/ and host_vars/ directories
# ✅ Use meaningful group names
# ✅ Encrypt sensitive vars with Ansible Vault
# ✅ Use dynamic inventory for cloud
# ✅ Keep inventory in version control

# ❌ Don't put passwords in inventory files
# ❌ Don't use IP addresses as hostnames (use DNS)
# ❌ Don't create groups with single hosts (unless meaningful)
# ❌ Don't duplicate variables across groups

# inventory/production/hosts.yml
all:
  children:
    webservers:
      hosts:
        web-[01:03].prod.example.com:
    dbservers:
      hosts:
        db-01.prod.example.com:
          role: primary
        db-02.prod.example.com:
          role: replica
    monitoring:
      hosts:
        mon-01.prod.example.com:
    production:
      children:
        webservers:
        dbservers:
        monitoring:
      vars:
        env: production
        ansible_user: deploy
        ansible_become: true
        ntp_server: time.prod.example.com