Ansible - Conditionals 🔛

Description 👀

Conditionals are used to control the flow of execution of tasks in Ansible. They are used to check the state of a system and then execute a task based on the result of the check.

Examples 🧩

• when example; installs nginx on Debian and RedHat based systems

    # when.yml
    ---
    - 
        name: install nginx
        hosts: all
        tasks:
            - 
                name: install nginx
                apt:
                    name: nginx
                    state: present
                when: ansible_os_family == "Debian"
            - 
                name: install nginx
                yum:
                    name: nginx
                    state: present
                when: ansible_os_family == "RedHat"
  

• record output of tasks; mail if service is not running (first checking the service)

    # register.yml
    ---
    - 
        name: Check Status of Services
        hosts: localhost
        tasks:
            -
                name: Check HTTPD Status
                command: service httpd status
                register: httpd_status
              
            -
                name: Mail HTTPD Status if not running
  
                mail:
                    to: someone@job.com
                    subject: "HTTPD is not running"
                    body: ""
                when: httpd_status.stdout.find("down") != -1
  

• loop example; installs packages based on requirement over an array of packages

    # loop.yml
    ---
    -
        name: Install Packages
        hosts: all
        vars:
            packages:
                - name: nginx
                required: True
                - name: httpd
                required: False
                - name: apache2
                required: False
        tasks:
            - 
                name: Install  (using apt)
                apt:
                    name: ""
                    state: present
                when: item.required == True
                loop: ""
  
  

  • use loops to create arrays
    • when looping over an array of dictionaries you are able to use dot notation for the nested items
    • arrays of dictionaries can also be represented in a json format

      # loop_arr.yml
      ---
      -
          name: Create Users
          hosts: localhost
          var:
              num_users: 6
          tasks:        
              -
                  name: Create Users
                  user:
                      name: ''
                      id: ''
                      state: present
                  loop:
                      - name: user_1
                        id: 1
                      - name: user_2 
                        id: 2
                      - name: user_3
                        id: 3
                      - name: user_4
                        id: 4
                      - name: user_5
                        id: 5
                      - name: user_6
                        id: 6
    
              -
                  name: Create Users (json)
                  user:
                      name: ''
                      id: ''
                      state: present
                  loop:
                      - {name: user_1, id: 1}
                      - {name: user_2, id: 2}
                      - {name: user_3, id: 3}
                      - {name: user_4, id: 4}
                      - {name: user_5, id: 5}
                      - {name: user_6, id: 6}
    
    

  • with_* directive lets you loop over a list of items
    • with_items is the most common
    • with_dict is used to loop over a dictionary
    • with_file is used to loop over a file
    • with_url is used to loop over urls
    • with_env is used to loop over environment variables
    • With_k8s is used to loop over kubernetes resources
    • With_inventory_hostnames is used to loop over inventory hostnames

      # with_star.yml
      ---
      -
          name: Create Users
          hosts: localhost
          var:
              num_users: 6
          tasks:        
              -
                  name: Create Users (with_items)
                  user:
                      name: ''
                      id: ''
                      state: present
                  with_items:
                      - name: user_1
                        id: 1
                      - name: user_2 
                        id: 2
                      - name: user_3
                        id: 3
                      - name: user_4
                        id: 4
                      - name: user_5
                        id: 5
                      - name: user_6
                        id: 6
    
              -
                  name: View Config Files (with_file)
                  debug: var=item
                  with_file:
                      - '/etc/hosts'
                      - '/etc/resolv.conf'
                      - '/etc/ntp.conf'
    
              -
                  name: Get From URLS (with_url)
                  debug: var=item
                  with_url:
                      - 'https://www.dell.com'
                      - 'https://www.google.com'
                      - 'https://www.amazon.com'
    

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