Learn the basics of Ansible!

Ansible is an automating tool used to manage multiple machines together. Usage examples include patching one to hundrades of machines with a single command. Or installing an application and configuring it over several servers. You can also deploy EC2 instances and configure them to the cloud, as used in Terraform.

Ansible depends mainly on the host file & modules. A host file is where the user identifies the IP addresses of the target machines. These IP address are categorized under group or set of groups.

[linux]
127.0.0.1  # ip
..         # ip2
.          # etc..

[linux: vars] # optional

Below linux:vars you may add parameters such as username and password credintials to login to the instances.

A library of programs that can be used as a task for a specific job. Such as bash module to write a script, a module to check the ping, and many other modules that can be found in the ansible modules.

Follow the offical documentation for installing Ansible.

All the ansible files are included in the /etc/ansible directory.

Here are examples of running ansible commands:

# Run a bash command using '-a'
 ansible GROUP_NAME -a "yum install httpd -y" --user=USERNAME_of_INSTANCE --key-file KEYPAIR.pem

# Run a module using '-m'
 ansible GROUP_NAME -m ping --user=USERNAME_of_INSTANCE --key-file KEYPAIR.pem -vvv #-vvv is used for logging

Note: If you register the username & password parameters in the hosts file, or you register the authorized keys in ssh cofiguration directory then you won't need to write the --user=USERNAME_of_INSTANCE --key-file KEYPAIR.pem each time.

An ansible book is a script file that contains one or multiple tasks in which each task assigned to a host and contains a single or multiple modules. ansible book file is useful to create a shareable configuration file that does a particular job. An Ansible book contains a play or multiple plays, each play has the host group identified and the tasks, where each task has a module to do a job.

Here is an example of apache.yml:

---
- name: shell commands     # Play
  hosts: linux                      # Group specified
  become: true      

  tasks:                                
    - name: Run shell commands          # Task1
      shell: |                          # Modlule 1: shell. The | symbol used to write multiple cammands 
        sudo yum install httpd -y
        echo "This page was configured by Ansible" >> /var/www/html/index.html
        service httpd restart
        echo "Done"

To run the script:

ansible-playbook apache.yml

Here is another example to check if Nano is installed on the servers, otherwise it will be installed:

---
- name: nano-checker     #Play
  hosts: linux                      #group specified
  become: true      

  tasks:                                
    - name: Check if nano installed          #task1
      yum:                          # modlule 1
        name: nano                  #package name
        state: latest               #check if latest version available. You can used "present" as well.

You can use absent at the state node, which will delete the package if found installed.