Where can I get a list of Ansible pre-defined variables?

I use this simple playbook:

---
# vars.yml
#
# Shows the value of all variables/facts.
#
# Example:
#
#   ansible-playbook vars.yml -e 'hosts=localhost'
#
- hosts: localhost
  tasks:
    - fail: "You must specify a value for `hosts` variable - e.g.: ansible-playbook vars.yml -e 'hosts=localhost'"
      when: hosts is not defined

- hosts: "{{ hosts }}"
  tasks:
    - debug: var=vars
    - debug: var=hostvars[inventory_hostname]

There are 3 sources of variables in Ansible:

  1. Variables gathered from facts. You can get them by running command: ansible -m setup hostname

  2. Built-in (pre-defined) Ansible variables (AKA 'magic' variables). They are documented in Ansible documentation: http://docs.ansible.com/playbooks_variables.html#magic-variables-and-how-to-access-information-about-other-hosts
    Here is the list extracted from Ansible 1.9 documentation:

    • group_names
    • groups
    • inventory_hostname
    • ansible_hostname
    • inventory_hostname_short
    • play_hosts
    • delegate_to
    • inventory_dir
    • inventory_file
  3. Variables passed to ansible via command line. But obviously you know what they are

ansible -m setup hostname

Only gets the facts gathered by the setup module.

Gilles Cornu posted a template trick to list all variables for a specific host.

Template (later called dump_variables):

HOSTVARS (ANSIBLE GATHERED, group_vars, host_vars) :

{{ hostvars[inventory_hostname] | to_yaml }}

PLAYBOOK VARS:

{{ vars | to_yaml }}

Playbook to use it:

- hosts: all
  tasks:
  - template:
      src: templates/dump_variables
      dest: /tmp/ansible_variables
  - fetch:
      src: /tmp/ansible_variables
      dest: "{{inventory_hostname}}_ansible_variables"

After that you have a dump of all variables on every host, and a copy of each text dump file on your local workstation in your tmp folder. If you don't want local copies, you can remove the fetch statement.

This includes gathered facts, host variables and group variables. Therefore you see ansible default variables like group_names, inventory_hostname, ansible_ssh_host and so on.


From the FAQ:

How do I see a list of all of the ansible_ variables?

Ansible by default gathers “facts” about the machines under management, and these facts can be accessed in playbooks and in templates. To see a list of all of the facts that are available about a machine, you can run the setup module as an ad hoc action:

ansible -m setup hostname

This will print out a dictionary of all of the facts that are available for that particular host. You might want to pipe the output to a pager.This does NOT include inventory variables or internal ‘magic’ variables. See the next question if you need more than just ‘facts’.

Here is the output for my vagrant virtual machine called scdev:

scdev | success >> {
    "ansible_facts": {                                                                                                 
        "ansible_all_ipv4_addresses": [                                                                                
            "10.0.2.15",                                                                                               
            "192.168.10.10"                                                                                            
        ],                                                                                                             
        "ansible_all_ipv6_addresses": [                                                                                
            "fe80::a00:27ff:fe12:9698",                                                                                
            "fe80::a00:27ff:fe74:1330"                                                                                 
        ],                                                                                                             
        "ansible_architecture": "i386",                                                                                
        "ansible_bios_date": "12/01/2006",                                                                             
        "ansible_bios_version": "VirtualBox",                                                                          
        "ansible_cmdline": {                                                                                           
            "BOOT_IMAGE": "/vmlinuz-3.2.0-23-generic-pae",                                                             
            "quiet": true,                                                                                             
            "ro": true,                                                                                                
            "root": "/dev/mapper/precise32-root"                                                                       
        },                                                                                                             
        "ansible_date_time": {                                                                                         
            "date": "2013-09-17",                                                                                      
            "day": "17",                                                                                               
            "epoch": "1379378304",                                                                                     
            "hour": "00",                                                                                              
            "iso8601": "2013-09-17T00:38:24Z",                                                                         
            "iso8601_micro": "2013-09-17T00:38:24.425092Z",                                                            
            "minute": "38",                                                                                            
            "month": "09",                                                                                             
            "second": "24",                                                                                            
            "time": "00:38:24",                                                                                        
            "tz": "UTC",                                                                                               
            "year": "2013"                                                                                             
        },                                                                                                             
        "ansible_default_ipv4": {                                                                                      
            "address": "10.0.2.15",                                                                                    
            "alias": "eth0",                                                                                           
            "gateway": "10.0.2.2",                                                                                     
            "interface": "eth0",                                                                                       
            "macaddress": "08:00:27:12:96:98",                                                                         
            "mtu": 1500,                                                                                               
            "netmask": "255.255.255.0",                                                                                
            "network": "10.0.2.0",                                                                                     
            "type": "ether"                                                                                            
        },                                                                                                             
        "ansible_default_ipv6": {},                                                                                    
        "ansible_devices": {                                                                                           
            "sda": {                                                                                                   
                "holders": [],                                                                                         
                "host": "SATA controller: Intel Corporation 82801HM/HEM (ICH8M/ICH8M-E) SATA Controller [AHCI mode] (rev 02)",                                                                                                                
                "model": "VBOX HARDDISK",                                                                              
                "partitions": {                                                                                        
                    "sda1": {                                                                                          
                        "sectors": "497664",                                                                           
                        "sectorsize": 512,                                                                             
                        "size": "243.00 MB",                                                                           
                        "start": "2048"                                                                                
                    },                                                                                                 
                    "sda2": {                                                                                          
                        "sectors": "2",                                                                                
                        "sectorsize": 512,                                                                             
                        "size": "1.00 KB",                                                                             
                        "start": "501758"                                                                              
                    },                                                                                                 
                },                                                                                                     
                "removable": "0",                                                                                      
                "rotational": "1",                                                                                     
                "scheduler_mode": "cfq",                                                                               
                "sectors": "167772160",                                                                                
                "sectorsize": "512",                                                                                   
                "size": "80.00 GB",                                                                                    
                "support_discard": "0",                                                                                
                "vendor": "ATA"                                                                                        
            },                                                                                                         
            "sr0": {                                                                                                   
                "holders": [],                                                                                         
                "host": "IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)",                           
                "model": "CD-ROM",                                                                                     
                "partitions": {},                                                                                      
                "removable": "1",                                                                                      
                "rotational": "1",                                                                                     
                "scheduler_mode": "cfq",                                                                               
                "sectors": "2097151",                                                                                  
                "sectorsize": "512",                                                                                   
                "size": "1024.00 MB",                                                                                  
                "support_discard": "0",                                                                                
                "vendor": "VBOX"                                                                                       
            },                                                                                                         
            "sr1": {                                                                                                   
                "holders": [],                                                                                         
                "host": "IDE interface: Intel Corporation 82371AB/EB/MB PIIX4 IDE (rev 01)",                           
                "model": "CD-ROM",                                                                                     
                "partitions": {},                                                                                      
                "removable": "1",                                                                                      
                "rotational": "1",                                                                                     
                "scheduler_mode": "cfq",                                                                               
                "sectors": "2097151",                                                                                  
                "sectorsize": "512",                                                                                   
                "size": "1024.00 MB",                                                                                  
                "support_discard": "0",                                                                                
                "vendor": "VBOX"                                                                                       
            }                                                                                                          
        },                                                                                                             
        "ansible_distribution": "Ubuntu",                                                                              
        "ansible_distribution_release": "precise",                                                                     
        "ansible_distribution_version": "12.04",                                                                       
        "ansible_domain": "",                                                                                          
        "ansible_eth0": {                                                                                              
            "active": true,                                                                                            
            "device": "eth0",                                                                                          
            "ipv4": {                                                                                                  
                "address": "10.0.2.15",                                                                                
                "netmask": "255.255.255.0",                                                                            
                "network": "10.0.2.0"                                                                                  
            },                                                                                                         
            "ipv6": [                                                                                                  
                {                                                                                                      
                    "address": "fe80::a00:27ff:fe12:9698",                                                             
                    "prefix": "64",                                                                                    
                    "scope": "link"                                                                                    
                }                                                                                                      
            ],                                                                                                         
            "macaddress": "08:00:27:12:96:98",                                                                         
            "module": "e1000",                                                                                         
            "mtu": 1500,                                                                                               
            "type": "ether"                                                                                            
        },                                                                                                             
        "ansible_eth1": {                                                                                              
            "active": true,                                                                                            
            "device": "eth1",                                                                                          
            "ipv4": {                                                                                                  
                "address": "192.168.10.10",                                                                            
                "netmask": "255.255.255.0",                                                                            
                "network": "192.168.10.0"                                                                              
            },                                                                                                         
            "ipv6": [                                                                                                  
                {                                                                                                      
                    "address": "fe80::a00:27ff:fe74:1330",                                                             
                    "prefix": "64",                                                                                    
                    "scope": "link"                                                                                    
                }                                                                                                      
            ],                                                                                                         
            "macaddress": "08:00:27:74:13:30",                                                                         
            "module": "e1000",                                                                                         
            "mtu": 1500,                                                                                               
            "type": "ether"                                                                                            
        },                                                                                                             
        "ansible_form_factor": "Other",                                                                                
        "ansible_fqdn": "scdev",                                                                                       
        "ansible_hostname": "scdev",                                                                                   
        "ansible_interfaces": [                                                                                        
            "lo",                                                                                                      
            "eth1",                                                                                                    
            "eth0"                                                                                                     
        ],                                                                                                             
        "ansible_kernel": "3.2.0-23-generic-pae",                                                                      
        "ansible_lo": {                                                                                                
            "active": true,                                                                                            
            "device": "lo",                                                                                            
            "ipv4": {                                                                                                  
                "address": "127.0.0.1",                                                                                
                "netmask": "255.0.0.0",                                                                                
                "network": "127.0.0.0"                                                                                 
            },                                                                                                         
            "ipv6": [                                                                                                  
                {                                                                                                      
                    "address": "::1",                                                                                  
                    "prefix": "128",                                                                                   
                    "scope": "host"                                                                                    
                }                                                                                                      
            ],                                                                                                         
            "mtu": 16436,                                                                                              
            "type": "loopback"                                                                                         
        },                                                                                                             
        "ansible_lsb": {                                                                                               
            "codename": "precise",                                                                                     
            "description": "Ubuntu 12.04 LTS",                                                                         
            "id": "Ubuntu",                                                                                            
            "major_release": "12",                                                                                     
            "release": "12.04"                                                                                         
        },                                                                                                             
        "ansible_machine": "i686",                                                                                     
        "ansible_memfree_mb": 23,                                                                                      
        "ansible_memtotal_mb": 369,                                                                                    
        "ansible_mounts": [                                                                                            
            {                                                                                                          
                "device": "/dev/mapper/precise32-root",                                                                
                "fstype": "ext4",                                                                                      
                "mount": "/",                                                                                          
                "options": "rw,errors=remount-ro",                                                                     
                "size_available": 77685088256,                                                                         
                "size_total": 84696281088                                                                              
            },                                                                                                         
            {                                                                                                          
                "device": "/dev/sda1",                                                                                 
                "fstype": "ext2",                                                                                      
                "mount": "/boot",                                                                                      
                "options": "rw",                                                                                       
                "size_available": 201044992,                                                                           
                "size_total": 238787584                                                                                
            },                                                                                                         
            {                                                                                                          
                "device": "/vagrant",                                                                                  
                "fstype": "vboxsf",                                                                                    
                "mount": "/vagrant",                                                                                   
                "options": "uid=1000,gid=1000,rw",                                                                     
                "size_available": 42013151232,                                                                         
                "size_total": 484145360896                                                                             
            }                                                                                                          
        ],                                                                                                             
        "ansible_os_family": "Debian",                                                                                 
        "ansible_pkg_mgr": "apt",                                                                                      
        "ansible_processor": [                                                                                         
            "Pentium(R) Dual-Core  CPU      E5300  @ 2.60GHz"                                                          
        ],                                                                                                             
        "ansible_processor_cores": "NA",                                                                               
        "ansible_processor_count": 1,                                                                                  
        "ansible_product_name": "VirtualBox",                                                                          
        "ansible_product_serial": "NA",                                                                                
        "ansible_product_uuid": "NA",                                                                                  
        "ansible_product_version": "1.2",                                                                              
        "ansible_python_version": "2.7.3", 
        "ansible_selinux": false, 
        "ansible_swapfree_mb": 766, 
        "ansible_swaptotal_mb": 767, 
        "ansible_system": "Linux", 
        "ansible_system_vendor": "innotek GmbH", 
        "ansible_user_id": "neves", 
        "ansible_userspace_architecture": "i386", 
        "ansible_userspace_bits": "32", 
        "ansible_virtualization_role": "guest", 
        "ansible_virtualization_type": "virtualbox"
    }, 
    "changed": false
}

The current documentation now has a complete chapter about Discovering variables: facts and magic variables.