infra-automation/cheatsheets/inventory.md

Inventory Cheatsheet

Quick reference for Ansible inventory management.

Quick Commands

List Hosts

# Static inventory
ansible all -i inventories/development/hosts.yml --list-hosts

# SSH config dynamic
ansible all -i plugins/inventory/ssh_config_inventory.py --list-hosts

# Libvirt dynamic
ansible all -i plugins/inventory/libvirt_kvm.py --list-hosts

View Inventory Structure

# List all groups and hosts
ansible-inventory -i <inventory> --list

# Show as graph
ansible-inventory -i <inventory> --graph

# Specific host details
ansible-inventory -i <inventory> --host <hostname>

Test Connectivity

# Ping all hosts
ansible all -i <inventory> -m ping

# Ping specific group
ansible kvm_guests -i <inventory> -m ping

# Verbose output
ansible all -i <inventory> -m ping -vvv

Inventory Locations

Inventory	Path	Type
Static Dev	inventories/development/hosts.yml	Static YAML
SSH Parser	plugins/inventory/ssh_config_inventory.py	Dynamic Script
Libvirt	plugins/inventory/libvirt_kvm.py	Dynamic Script

Common Groups

Group	Description	Inventory
all	All hosts	All
external_hosts	Public-facing hosts	All
hypervisors	KVM hypervisors	All
kvm_guests	All VMs	All
running_vms	Running VMs only	Libvirt
dns_servers	DNS/DHCP servers	All
mail_servers	Mail servers	All
development	Dev/test hosts	All

Dynamic Inventory Usage

SSH Config Parser

# List inventory
python3 plugins/inventory/ssh_config_inventory.py --list

# Host details
python3 plugins/inventory/ssh_config_inventory.py --host pihole

# Use with ansible
ansible all -i plugins/inventory/ssh_config_inventory.py -m ping

Libvirt Dynamic

# Set environment
export LIBVIRT_DEFAULT_URI="qemu+ssh://grok@grok.home.serneels.xyz/system"
export LIBVIRT_HYPERVISOR_NAME="grokbox"

# List VMs
python3 plugins/inventory/libvirt_kvm.py --list

# Use with ansible
ansible running_vms -i plugins/inventory/libvirt_kvm.py -m setup

Playbook Execution

Single Inventory

ansible-playbook -i inventories/development/hosts.yml site.yml

Multiple Inventories

ansible-playbook \
  -i inventories/development/hosts.yml \
  -i plugins/inventory/libvirt_kvm.py \
  site.yml

With Limits

# Limit to specific group
ansible-playbook -i <inventory> --limit kvm_guests site.yml

# Limit to specific host
ansible-playbook -i <inventory> --limit pihole site.yml

# Multiple limits
ansible-playbook -i <inventory> --limit "dns_servers:mail_servers" site.yml

Variable Precedence

From lowest to highest:

1. group_vars/all.yml
2. group_vars/<group_name>.yml
3. host_vars/<hostname>.yml
4. Playbook vars
5. Extra vars (-e)

Debugging

Validate Inventory

# Syntax check
ansible-inventory -i <inventory> --list > /dev/null

# YAML validation
yamllint inventories/development/hosts.yml

Connection Test

# Test SSH connectivity
ansible all -i <inventory> -m ping -vvv

# Check Python interpreter
ansible all -i <inventory> -m setup -a "filter=ansible_python_version"

# Verify become/sudo
ansible all -i <inventory> -m shell -a "whoami" --become

View Effective Variables

# All variables for a host
ansible-inventory -i <inventory> --host <hostname> --yaml

# Specific variable
ansible <hostname> -i <inventory> -m debug -a "var=ansible_user"

Common Issues

SSH Config Parser

Issue: Hosts missing Fix: Check ~/.ssh/config syntax and permissions

Libvirt Dynamic

Issue: python3-libvirt not found Fix: apt-get install python3-libvirt (Debian) or dnf install python3-libvirt (RHEL)

Issue: Connection failed Fix: Test SSH: ssh grok@grok.home.serneels.xyz

Static Inventory

Issue: YAML errors Fix: Check indentation, validate with yamllint

Issue: Variables not applied Fix: Check file naming in group_vars/ matches group name

Performance Tips

# ansible.cfg
[defaults]
forks = 20
gathering = smart
fact_caching = jsonfile
fact_caching_timeout = 86400

# SSH connection reuse (~/.ssh/config)
Host *
  ControlMaster auto
  ControlPersist 600s

Quick Setup

# Create inventory structure
mkdir -p inventories/{production,staging,development}/{group_vars,host_vars}

# Test connectivity
ansible all -i <inventory> -m ping

# Gather facts
ansible all -i <inventory> -m setup --tree /tmp/facts

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See also: /opt/ansible/docs/inventory.md for complete documentation