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skills/ansible/references/inventory.md

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+# Ansible Inventory Reference
+
+## YAML Inventory Format
+
+```yaml
+all:
+  children:
+    webservers:
+      hosts:
+        web1:
+          ansible_host: 192.168.1.10
+        web2:
+          ansible_host: 192.168.1.11
+      vars:
+        http_port: 80
+
+    databases:
+      hosts:
+        db1:
+          ansible_host: 192.168.1.20
+          db_port: 5432
+        db2:
+          ansible_host: 192.168.1.21
+
+    production:
+      children:
+        webservers:
+        databases:
+
+  vars:
+    ansible_user: ubuntu
+    ansible_ssh_private_key_file: ~/.ssh/id_rsa
+```
+
+## INI Inventory Format
+
+```ini
+[webservers]
+web1 ansible_host=192.168.1.10
+web2 ansible_host=192.168.1.11
+
+[webservers:vars]
+http_port=80
+
+[databases]
+db1 ansible_host=192.168.1.20 db_port=5432
+db2 ansible_host=192.168.1.21
+
+[production:children]
+webservers
+databases
+
+[all:vars]
+ansible_user=ubuntu
+```
+
+## Host Variables
+
+Common host variables:
+
+| Variable | Purpose |
+|----------|---------|
+| `ansible_host` | IP or hostname to connect |
+| `ansible_port` | SSH port (default: 22) |
+| `ansible_user` | SSH username |
+| `ansible_ssh_private_key_file` | SSH key path |
+| `ansible_become` | Enable sudo |
+| `ansible_become_user` | Sudo target user |
+| `ansible_python_interpreter` | Python path |
+
+## Group Variables
+
+```yaml
+# group_vars/webservers.yml
+http_port: 80
+document_root: /var/www/html
+
+# group_vars/all.yml
+ntp_server: time.example.com
+dns_servers:
+  - 8.8.8.8
+  - 8.8.4.4
+```
+
+## Host Variables Files
+
+```yaml
+# host_vars/web1.yml
+site_name: production-web1
+ssl_cert_path: /etc/ssl/certs/web1.crt
+```
+
+## Dynamic Groups
+
+```yaml
+# In playbook
+- hosts: "{{ target_group | default('all') }}"
+```
+
+Run with:
+```bash
+ansible-playbook playbook.yml -e "target_group=webservers"
+```
+
+## Patterns
+
+```bash
+# All hosts
+ansible all -m ping
+
+# Single host
+ansible web1 -m ping
+
+# Group
+ansible webservers -m ping
+
+# Multiple groups
+ansible 'webservers:databases' -m ping
+
+# Intersection (AND)
+ansible 'webservers:&production' -m ping
+
+# Exclusion
+ansible 'webservers:!web1' -m ping
+
+# Regex
+ansible '~web[0-9]+' -m ping
+```
+
+## Limit
+
+```bash
+# Limit to specific hosts
+ansible-playbook playbook.yml -l web1
+ansible-playbook playbook.yml --limit web1,web2
+ansible-playbook playbook.yml --limit 'webservers:!web3'
+```
+
+## Inventory Check
+
+```bash
+# List hosts
+ansible-inventory --list
+ansible-inventory --graph
+
+# Host info
+ansible-inventory --host web1
+
+# Validate
+ansible all --list-hosts
+```
+
+## Multiple Inventories
+
+```bash
+# Multiple files
+ansible-playbook -i inventory/production -i inventory/staging playbook.yml
+
+# Directory of inventories
+ansible-playbook -i inventory/ playbook.yml
+```
+
+## Special Groups
+
+| Group | Contains |
+|-------|----------|
+| `all` | All hosts |
+| `ungrouped` | Hosts not in any group |
+
+## Local Connection
+
+```yaml
+localhost:
+  ansible_host: 127.0.0.1
+  ansible_connection: local
+```
+
+Or in inventory:
+```ini
+localhost ansible_connection=local
+```