Red Hat Enterprise Linux Automation with Ansible

Procedure 4.1. Instructions

1. On the workstation machine, change to the /home/student/control-flow directory.

   [student@workstation ~]$ cd ~/control-flow
   [student@workstation control-flow]$

2. The lab command created an Ansible configuration file as well as an inventory file. The inventory file contains the servera.lab.example.com server in the database_dev host group, and the serverb.lab.example.com server in the database_prod host group. Review the contents of the file before proceeding.

   [student@workstation control-flow]$ cat inventory
   [database_dev]
   servera.lab.example.com
   
   [database_prod]
   serverb.lab.example.com

3. Create the playbook.yml playbook, which contains a play with two tasks. Use the database_dev host group. The first task installs the MariaDB required packages, and the second task ensures that the MariaDB service is running.

   1. Create the playbook.yml playbook and define the mariadb_packages variable with two values: mariadb-server and python3-PyMySQL.

      ---
      - name: MariaDB server is running
        hosts: database_dev
        vars:
          mariadb_packages:
            - mariadb-server
            - python3-PyMySQL

   2. Define a task that uses the ansible.builtin.dnf module and the mariadb_packages variable. The task uses the mariadb_packages variable to install the required packages.

        tasks:
          - name: MariaDB packages are installed
            ansible.builtin.dnf:
              name: "{{ item }}"
              state: present
            loop: "{{ mariadb_packages }}"

      Important

      Using loop is not the most efficient way to install packages. In the preceding code, the ansible.builtin.dnf module runs once for each package in the mariadb_packages list.

      Normally, you should install all the packages as one transaction, by passing the entire list of packages to the module, rather than passing it one module at a time:

      - name: MariaDB packages are installed
        ansible.builtin.dnf:
          name: "{{ mariadb_packages }}"
          state: present

      However, other modules like ansible.builtin.user do not allow you to do this; you have to pass that module one user to operate upon at a time. In those cases, loop is an invaluable tool.

      This example is simply meant as a way for you to see how loop works.

   3. Define a second task to start the mariadb service. The full playbook should consist of the following content:

      - name: MariaDB server is running
        hosts: database_dev
        vars:
          mariadb_packages:
            - mariadb-server
            - python3-PyMySQL
      
        tasks:
          - name: MariaDB packages are installed
            ansible.builtin.dnf:
              name: "{{ item }}"
              state: present
            loop: "{{ mariadb_packages }}"
      
          - name: Start MariaDB service
            ansible.builtin.service:
              name: mariadb
              state: started
              enabled: true

4. Run the playbook and watch the output of the play.

   [student@workstation control-flow]$ ansible-navigator run \
   > -m stdout playbook.yml
   
   PLAY [MariaDB server is running] ***********************************************
   
   TASK [Gathering Facts] *********************************************************
   ok: [servera.lab.example.com]
   
   TASK [MariaDB packages are installed] ******************************************
   changed: [servera.lab.example.com] => (item=mariadb-server)
   changed: [servera.lab.example.com] => (item=python3-PyMySQL)
   
   TASK [Start MariaDB service] ***************************************************
   changed: [servera.lab.example.com]
   
   PLAY RECAP *********************************************************************
   servera.lab.example.com    : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

5. Update the first task to only run if the managed host uses Red Hat Enterprise Linux as its operating system. Update the play to use the database_prod host group.

   - name: MariaDB server is running
     hosts: database_prod
     vars:
   ...output omitted...
     tasks:
       - name: MariaDB packages are installed
         ansible.builtin.dnf:
           name: "{{ item }}"
           state: present
         loop: "{{ mariadb_packages }}"
         when: ansible_facts['distribution'] == "RedHat"
   ...output omitted...

6. Run the playbook again and watch the output of the play.

   [student@workstation control-flow]$ ansible-navigator run \
   > -m stdout playbook.yml
   
   PLAY [MariaDB server is running] ***********************************************
   
   TASK [Gathering Facts] *********************************************************
   ok: [serverb.lab.example.com]
   
   TASK [MariaDB packages are installed] ******************************************
   ok: [serverb.lab.example.com] => (item=mariadb-server)
   ok: [serverb.lab.example.com] => (item=python3-PyMySQL)
   
   TASK [Start MariaDB service] ***************************************************
   ok: [serverb.lab.example.com]
   
   PLAY RECAP *********************************************************************
   serverb.lab.example.com    : ok=3    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

   Ansible executes the task because serverb.lab.example.com uses Red Hat Enterprise Linux.