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Basic

Define environment variables

hosts: REPLACE_HOST_ALIAS
environment:
  REPLACE_VAR_NAME_1: "REPLACE_VAR_VALUE_1"
  REPLACE_VAR_NAME_2: "{{ ansible_env.PATH }}:REPLACE_RELATIVE_PATH"
  sample_value_map:
    - {name: "name 1", description:"description 1", field1: "...", ...}
    - {name: "name 2", description:"description 2", field1: "...", ...} 
  ...

Save the output in a variable

- name: REPLACE_TASK_NAME
  register: variable_name

Read configs from a yml file

- name: Load the configuration file 
  include_vars: 
    file: "{{ configuration_file }}" 
    name: my_vars
...
- name: REPLACE_TASK_NAME
  # Replace action using the var e.g. my_vars[x].z

 Not mark the task as changed

For read-only commands that are not changing anything on the host. E.g. check if services are up after an upgrade

- name: REPLACE_TASK_NAME
  changed_when: False

Perform an action based on the host name

- name: REPLACE_TASK_NAME
  when: REPLACE_CONDITION # Example: "'host_prefix' in inventory_hostname

Iterate over a loop

- name: REPLACE_TASK_NAME
  # Replace action using{{ item }}"
  with_items: [item_A,item_B...]

Alternatively:

- name: REPLACE_TASK_NAME
  # Replace action using{{ item }}"
  with_items:
    - item_A
    - item_B
    ...

Trigger a handler when a task is performed

E.g. to restart a service after updating some config files

tasks:
  - name: Write the apache config file
    ...
    notify:
      - REPLACE_HANDLER_NAME

handlers:
  - name: REPLACE_HANDLER_NAME
    ...

Separate pre-condition, main tasks and post-conditions

pre_tasks: 
...
tasks: 
... 
post_tasks: 
...

Wait for tasks to complete on other hosts

tasks: 
- name: Phase 1
  block:
  - name: task phase 1
- name: Phase 2
  block:
  - name: task phase 2
...

Load tasks from another file

To simplify complex scripts without using roles:

- name: REPLACE_TASK_NAME
  include_tasks: 
    file: REPLACE_RELATIVE_PATH

 Run as a privileged user

become: yes
become_method: su
become_user: REPLACE_USER

Run the same scripts on different ports or by different users

[REPLACE_HOST_ALIAS]
REPLACE_DNS_1  ansible_port=REPLACE_PORT_1   ansible_user=REPLACE_USERNAME_1
REPLACE_DNS_2  ansible_port=REPLACE_PORT_2   ansible_user=REPLACE_USERNAME_2
...

Configure max time to connect to a host

Add this parameter to the SSH connection:

-o ServerAliveInterval=NumberOfSeconds

Conditionals

For example if we have different paths on modern and legacy hosts:

"{% if var_name == 'xxx' %}'value 1'{% else %}'value 2'{% endif %}"

Multi-line debug

- name: REPLACE_TASK_NAME
  debug:
    msg:
      - "Debug line 1"
      - "Debug line 2"
      ...

Common tasks

Check if a file exists

- name: REPLACE_TASK_NAME
  stat: 
    path: "{{ PATH_VARIABLE_NAME }}" 
  check_mode: no
  register: file_stat
  failed_when: not file_stat.stat.exists

Check if a file’s content matches the expected content

- name: REPLACE_TASK_NAME
  src: PATH_FILE_EXPECTED_CONTENT
  dest: PATH_FILE_IN_HOST
  backup: yes

Create a folder

- name: Create a folder
  file: path: REPLACE_PATH
  state: directory

- name: Copy a file to a folder 
  copy: 
    src: REPLACE_LOCAL_PATH
    dest: REPLACE_DESTINATION_PATH

- name: Delete a file file
  path: REPLACE_FILE_PATH
  state: absent

- name: Uncompress a file
  unarchive: 
    src: REPLACE_FILE_PATH
    dest: REPLACE_DESTINATION_FOLDER
    remote_src: yes # so it looks for it on the host

Set a symbolic link

- name: REPLACE_TASK_NAME
  file: 
    src: "REPLACE_TARGET_PATH"
    dest: "REPLACE_LINK_PATH"
    state: link 
    force: true

Check an endpoint is working and returning the expected content

- name: REPLACE_TASK_NAME
  url: "REPLACE_ENDPOINT"
  return_content: yes
  register: response
  until: 'REPLACE_EXPECTED_CONTENT_IN_RESPONSE in response.content' 
  retries: REPLACE_MAX_NUMBER_RETRIES
  delay: REPLACE_DELAY_TIME

Download a repository from Git

- name: REPLACE_TASK_NAME
  git: 
    repo: REPLACE_CLONE_URL
    dest: REPLACE_DESTINATION_PATH
    clone: yes
    update: yes

Service management

Check a service is started and enabled on boot

- name: REPLACE_TASK_NAME
  service:
    name: REPLACE_SERVICE_NAME
    state: started 
    enabled: yes

Restart a service

- name: REPLACE_TASK_NAME
  service:
    name: REPLACE_SERVICE_NAME
    state: restarted

Application management

Check if some applications have been installed with yum

- name: REPLACE_TASK_NAME
  name: REPLACE_APP_NAMES_SEPARATED_COMMAS
  state: present

Check if we are using the latest version of an app installed with yum

- name: REPLACE_TASK_NAME
  ansible.builtin.yum:
    name: REPLACE_APP_NAME
    state: latest

Check if an application has been installed with pip

- name: REPLACE_TASK_NAME
  name: REPLACE_APP_NAME
  state: present

User management

Create a list of user groups

- name: REPLACE_TASK_NAME
  group:
    name: "{{ item }}" 
  loop:
    - REPLACE_GROUP_NAME_1
    - REPLACE_GROUP_NAME_2
    - ...

Create a list of users

- name: REPLACE_TASK_NAME
  user:
    name: "{{ item.name }}" 
    group: "{{ item.group }}" 
    groups: "{{ item.groups }}" 
    uid: "{{ item.uid }}" 
    state: "{{ item.state }}"
  loop: 
    - { name: 'REPLACE', group: 'REPLACE', groups: 'REPLACE', uid: 'REPLACE', state: 'present' }
    - ...

To update a list of users and delete one, simply replace “present” by absent