Ansible - Modules ⚙️

Description 👀

Ansible contains several modules grouped in different categories.

Some categories are:

• system - actions to be performed at a system level
  • modifying users, groups, iptables, firewall configs
  • working with services
• commands - used to execute commands or scripts on a host
  • simple commands using the command module
  • interactive execution using the expect module by responding to prompts
  • run scripts on the host using the script module
• files - helps work with files
  • use the archive and un-archive modules to archive and unarchive files…
  • use find, inlinefile, and replace to modify file contents
• and many others..

Basics 📝

• command module parameters
  • chdir - change directory before executing the command
  • creates - a filename, when it already exists, this step will be skipped
  • executable - change the shell used to execute the command, should be an absolute path
  • free_form - the command module takes a free form command to run
  • removes - remove the file after execution if it exists
  • warn - warn when the command changes things
• script module
  1. copy scripts to the remote systems
  2. execute scripts on remote systems

  - 
    name: <play-name>
    hosts: <host-pattern>
    tasks:
    - name: <task-name>
      script: <path-to/script.sh> <script-args>
  

• service module
  • manage services - start, stop, restart

  - 
    name: <play-name>
    hosts: <host-pattern>
    tasks:
    - name: <task-name>
      service: name=<service-name> state=<service-state>
  

  • alternate method of creation using yml dictionary

    - 
      name: <play-name>
      hosts: <host-pattern>
      tasks:
      - name: <task-name>
        <module>:
          name: <service-name>
          state: <service-state>
    

    • they are one and the same

Examples 🧩

• command module

• script module play

  - 
    name: Sample Script Play - Create Target Log Directory
    hosts: localhost
    tasks:
    - name: create the target log directory
      script: create_script.sh 
  

• service module play

  - 
    name: Samlple Service Play - Start Postgres Service
    hosts: localhost
    tasks:
    - name: Start postgres service
      service: name=postgresql state=started
  

  • why is the state started, and not start?
    • if the service is already running, the state started will not cause any changes, this is called idempotent
  • started, stopped, restarted ensure that the service is in the desired state

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