Ansible - Variables

• letter, number, underscore, start with letter
• use with Jinja2 templating system
• “ansible allows Jinja2 loops and conditionals in templates, but in playbooks we do not use them”

Basic Variable Use

Defining a variable:

- hosts: webservers
  vars:
    http_port: 80

Using a variable in a template:

This is the report.
Listening on port {{ http_port }}

In a playbook:

template:
  src=settings.cfg.j2
  dest={{ remote_install_path }}/settings.cfg

In a playbook:

tasks:

  - name: create a virtual host file for {{ vhost }}
    template:
      src: somefile.j2
      dest: /etc/httpd/conf.d/{{ vhost }}

Registered Variables

• only in mem and only for current playbook run

Register a variable and print it:

- name: Get Uptime and Register
  ansible.builtin.shell: /usr/bin/uptime
  register: result

- name: Print Var
  ansible.builtin.debug:
    var: result

- name: Print Var
  ansible.builtin.debug:
    msg: This is it: {{ result }}

Perform action conditionally based on result of a registered variable:

- shell: /usr/bin/test_check
  register: result
  ignore_errors: True

- shell: /usr/bin/bar
  when: result.rc == 5

Checking results with a registered variable:

  tasks:

      - shell: cat /etc/motd
        register: motd_contents

      - shell: echo "motd contains the word hi"
        when: motd_contents.stdout.find('hi') != -1

Use registered variable in a loop if it is a list or converted to a list:

    - name: retrieve the list of home directories
      command: ls /home
      register: home_dirs

    - name: add home dirs to the backup spooler
      file:
        path: /mnt/bkspool/{{ item }}
        src: /home/{{ item }}
        state: link
      loop: "{{ home_dirs.stdout_lines }}"
      # same as loop: "{{ home_dirs.stdout.split() }}"

Check if empty:

      - name: list contents of directory
        command: ls mydir
        register: contents

      - name: check contents for emptiness
        debug:
          msg: "Directory is empty"
        when: contents.stdout == ""

External Variables File

Reference vars file in playbook:

- hosts: all
  remote_user: root
  vars:
    favcolor: blue
  vars_files:
    - /vars/external_vars.yml

Vars file example:

---
somevar: somevalue
password: magic
a: 1
b: 2
c: 3
list1:
  - apple
  - banana
  - toast
var1: "test"

Prompt for Variables

You can prompt for variables. This can be done for passwords. You would probably be better off just specifying “-kKb” on the command line.

---
- name: A Test Playbook
  hosts: all
  become: true
  vars_prompt:
    - name: ansible_password
      prompt: "Enter password"
      private: yes
    - name: ansible_become_password
      prompt: "Enter sudo password"
      private: yes

  tasks:
    - name: First Test
      command: "uname -a"

Vars on Commandline:

ansible-playbook release.yml -e "version=1.23.45 other_variable=foo"
ansible-playbook release.yml --extra-vars "version=1.23.45 other_variable=foo"

Use JSON if you want values other than strings:

ansible-playbook release.yml --extra-vars '{"version":"1.23.45","other_variable":"foo"}'

Vars from JSON or YAML file:

ansible-playbook release.yml --extra-vars "@some_file.json"

Unsafe variables:

var1: !unsafe 'this variable has {{ characters that should not be treated as a jinja2 template'

Unsafe / raw section of a template:

NOTE - Ignore the slashes in this example. This page was generated with markdown. I’m using these exact same tags to contain this code block and I couldn’t get that to work right with these tags …..

\{% raw %\} ... \{% endraw %\}

Common Magic Variables

hostvars	vars on other host
groups	all hosts and groups in inventory
group_names	group names for current host
inventory_hostname	hostname as shown in inventory
inventory_hostname_short	hostname as shown in inventory ( just the host part )
ansible_play_hosts	hosts in the play
ansible_play_batch	hosts in current batch of play
ansible_playbook_python	python path used to run ansible commandline
inventory_dir	host file dir
inventory_file	host file
playbook_dir	playbook base dir
role_path	current role path name

Ex, all IPs in a group:

{% for host in groups['app_servers'] %}
   {{ hostvars[host]['ansible_facts']['eth0']['ipv4']['address'] }}
{% endfor %}

YAML Anchors and Aliases

«  merge operator &jvm_opts # anchor *jvm_opts # alias

---
...
vars:
    app1:
        jvm: &jvm_opts
            opts: '-Xms1G -Xmx2G'
            port: 1000
            path: /usr/lib/app1
    app2:
        jvm:
            <<: *jvm_opts
            path: /usr/lib/app2

Another example:

vars:
  webapp:
      version: &my_version 1.0
      custom_name:
          - "ToDo_App"
          - *my_version