I have for example this playbook:

- name: System Configuration
  hosts: host1, host2
  become: yes
  tasks: 
    - name: Set current app version
      shell: export APP_VERSION={{ app_version|quote }}

I wish to set this variables for multiple hosts, for example host and host2. I read somewhere that I can create a yml file with the name of each host and store the variables fort each host there but I cane find how to load this file for each host.

I thought it may be loaded automatically if the name matches the host name but I dont think this happens I get an error FAILED! => {"msg": "The task includes an option with an undefined variable

so how can I define a set for variables for each host separately?

CodePudding user response：

There are many options.

1. For example, create a dictionary in 'group_vars/all'

shell> cat group_vars/all 
app_versions:
  host1: '1.1'
  host2: '1.2'
  default: '1.0'
app_version: "{{ app_versions[inventory_hostname]|
                 default(app_versions.default) }}"

The playbook

- hosts: host1,host2,host3
  tasks:
    - debug:
        var: app_version

gives

TASK [debug] **********************************************************
ok: [host3] => 
  app_version: '1.0'
ok: [host1] => 
  app_version: '1.1'
ok: [host2] => 
  app_version: '1.2'

2. The next option is 'vars_files'. Create a YAML file and use it in the playbook. For example, the file and the playbook give the same result

shell> cat app_versions.yml
app_versions:
  host1: '1.1'
  host2: '1.2'
  default: '1.0'
app_version: "{{ app_versions[inventory_hostname]|
                 default(app_versions.default) }}"

- hosts: host1,host2,host3
  vars_files:
    - app_versions.yml
  tasks:
    - debug:
        var: app_version

3. The next option is to create files in host_vars. For example, the 'host_vars' and the playbook give also the same result

shell> cat host_vars/host1.yml 
app_version: '1.1'

shell> cat host_vars/host2.yml 
app_version: '1.2'

shell> cat host_vars/host3.yml 
app_version: '1.0'

- hosts: host1,host2,host3
  tasks:
    - debug:
        var: app_version

The options override each other. See Understanding variable precedence. In the above options, the lowest precedence (4,5) are group_vars/all followed by host_vars precedence (9,10). The highest precedence (14) has the play vars_file.

Putting it all together, you might want to put the defaults to the group_vars/all

shell> cat group_vars/all
app_versions:
  default: '1.0'

and override the defaults in host_vars

shell> tree host_vars
host_vars
├── host1.yml
└── host2.yml

shell> cat host_vars/host1.yml 
app_version: '1.1'

shell> cat host_vars/host2.yml 
app_version: '1.2'

Then, the playbook below gives again the same result

- hosts: host1,host2,host3
  tasks:
    - set_fact:
        app_version: "{{ app_version|
                         default(app_versions[inventory_hostname])|
                         default(app_versions.default) }}"
    - debug:
        var: app_version

CodePudding user response：

Ok there are probably many solutions to this but the one I liked an used is to create a vars sub-directory in my project folder. Ansible look there by default when trying to find variable files for a host with the include_vars module.

So in my tasks I added this task:

  tasks:
    - name: Load variables for host
      include_vars: 
        file: "{{ inventory_hostname }}.yml"

and in my project in the vars directory I added a host_name_as_in_inventory.yml file with the host-name for each host I want to specify variables for.

Edit: as it is suggested int he other coment if the yml files with the hostnames are added in a directory calles host_vars they are loaded automatically so the include_vars taks is redundant.