Looping

Sometimes you want to repeat a task for several items. This can be done using a loop.

Note: loop is more recent; looping used to be done using with_items. Both are fine, if you have are writing code, using loop is preferred.

- name: Install tools
  hosts: all

  tasks:
    - name: Install tool
      apt:
        name: "{{ item }}"
      loop:
        - tcpdump
        - screen
        - nc

The a above task will run 3 times, once for each item in the list.

Sometimes you want to loop over a list of items with extra parameters:

- name: Install tools
  hosts: all

  tasks:
    - name: Install tool
      apt:
        name: "{{ item.name }}"
        state: "{{ item.state }}"
      loop:
        - name: tcpdump
          state: present
        - name: screen
          state: absent

The above task will run 2 times, once for each item in the list. Each item is a dictionary with 2 keys: name and state. Using a value from a dictionary is done using the dot notation: item.name or item.state.

You can make the above code even cooler by using a default value of present.

- name: Install tools
  hosts: all

  tasks:
    - name: Install tool
      apt:
        name: "{{ item.name }}"
        state: "{{ item.state | default('present') }}"
      loop:
        - name: tcpdump
        - name: screen
          state: absent

In the above example, the package under name will be installed by default. Only when specifying state: absent the package will be removed.

loop_control

When looping over a list of dictionaries, the output can become cluttered. You can use loop_control to change the output.

- name: Install tools
  hosts: all

  tasks:
    - name: Install tool
      apt:
        name: "{{ item.name }}"
        state: "{{ item.state | default('present') }}"
      loop:
        - name: tcpdump
        - name: screen
          state: absent
      loop_control:
        label: ""

Now the ouput will not show the whole dictionary, but only the value of item.name.

Instead of item, you can also rename the variable to something else:

- name: Install tools
  hosts: all

  tasks:
    - name: Install tool
      apt:
        name: "{{ tool.name }}"
        state: "{{ tool.state | default('present') }}"
      loop:
        - name: tcpdump
        - name: screen
          state: absent
      loop_control:
        label: "{{ tool.name }}"
        loop_var: tool

This renaming can be useful when looping over a list of dictionaries, with in the dictionary another list. Without renaming, you may end up with something like ``.

Assignment

Create a playbook to create users. The playbook should create 2 users, with a specific name and comment.

Note: you can add --check or -C to run the playbook without making any changes. Sort of a dry-run to see what would happen.