Ansible Loops

This repository uses a simple Vagrantfile and a basic playbook to illustrate the use of some of the types of loops available inside Ansible.

Getting started

Install required tools

1. Ansible
2. Vagrant

Get and run the code

1. git clone git@github.com:ctorgalson/ansible-loops.git
2. cd ansible-loops
3. vagrant up
4. (After changing something in the playbook) vagrant provision

The example tasks

The included playbook contains a series of examples meant to illustrate one of Ansible's loop constructs or some related concept. The actual tasks performed are mostly arbitrary, but are directly applicable to the day-to-day use of Ansible.

Loop 1: create users using with_items.

The first example uses the with_items loop to ensure that two users are present on the target system:

# Variables for Loop 1.
users_with_items:
  - name: "alice"
    personal_directories:
      - "bob"
      - "carol"
      - "dan"
  - name: "bob"
    personal_directories:
      - "alice"
      - "carol"
      - "dan"

- name: "Loop 1: create users using 'with_items'."
  user:
    name: "{{ item.name }}"
  with_items: "{{ users_with_items }}"

Loop 2: create common users' directories using with_nested.

The second example builds on Loop 1 to ensure that each of the users' home directories contain two additional folders:

# Variables for Loop 2 (also uses `users_with_items` from Loop 1).
common_directories:
  - ".ssh"
  - "loops"

- name: "Loop 2: create common users' directories using 'with_nested'."
  file:
    dest: "/home/{{ item.0.name }}/{{ item.1 }}"
    owner: "{{ item.0.name }}"
    group: "{{ item.0.name }}"
    state: directory
  with_nested:
    - "{{ users_with_items }}"
    - "{{ common_directories }}"

Loop 3: create personal users' directories using with_subelements.

The third example re-uses the users_with_items variable from Loop 1 to create a unique set of directories in each user's home directory using with_subelements:

- name: "Loop 3: create personal users' directories using 'with_subelements'."
  file:
    dest: "/home/{{ item.0.name }}/{{ item.1 }}"
    owner: "{{ item.0.name }}"
    group: "{{ item.0.name }}"
    state: directory
  with_subelements:
    - "{{ users_with_items }}"
    - personal_directories

Loop 4: create users using 'with_dict'.

The fourth example show how to use the with_dict type of loop:

# Variables for Loop 4 (also uses `common_directories` from Loop 2).
users_with_dict:
  carol:
    common_directories: "{{ common_directories }}"
  dan:
    common_directories: "{{ common_directories }}"

- name: "Loop 4: create users using 'with_dict'."
  user:
    name: "{{ item.key }}"
  with_dict: "{{ users_with_dict }}"

Loop 5: create personal directories if they don't exist.

The fifth example shows one of the limitations of the with_dict loop from Loop 4, how to register a variable and loop over it, and how to use a jinja2 filter to transform some existing variables into a more usable form:

- name: "Get list of extant users."
  args:
    chdir: "/home"
  shell: "find * -type d -prune -not -path vagrant | sort"
  register: "home_directories"
  changed_when: false

- name: "Loop 5: create personal user directories if they don't exist."
  file:
    dest: "/home/{{ item.0 }}/{{ item.1 }}"
    owner: "{{ item.0 }}"
    group: "{{ item.0 }}"
    state: directory
  with_nested:
    - "{{ home_directories.stdout_lines }}"
    - "{{ home_directories.stdout_lines | union(common_directories) }}"
  when: "'{{ item.0 }}' != '{{ item.1 }}'"

Loop 6: list user directory contents and verify playbook results.

The final loop shows another example of how to iterate over a registered variable, as well as another way of using jinja2 filters to make debug output easier to read.

- name: "Loop 6: list user directory contents."
  args:
    chdir: "/home/{{ item }}"
  shell: "pwd && find -type d | sort"
  register: directory_contents
  with_items: "{{ home_directories.stdout_lines }}"
  changed_when: false

- name: "Verify playbook results."
  debug:
    msg: "{{ directory_contents.results | map(attribute='stdout_lines') | list }}"