day45.md

On the forty fifth day, I learned the following things about Ansible.

Playbook

• More than one command present in a YAML file will be called playbook. The combination of modules is called playbook.

• Playbook in ansible is written in YAML format.

• It is a human readable data serialzation language. It is commonly used for configuration.

• Playbook is like a file where you write code consist of vars, handlers, files, templates, and roles.

• Each playbook is composed of one or more "modules" in a list. Module is a list of configuration files.

• Playbook is divided into many sections.

  • Target section: Defines the host against which playbook task has to be executed.

  • Variable section: Defines variables. If there are multiple variables then just change a first variable and it will update all the values.

  • Task section: List of all modules that need to run in an order.

YAML

• For ansible, nearly every YAML file starts with a list.

• Each item in a list is a list of key-value pairs commonly called a dictionary.

• All the YAML files will begin with --- and end with ...

• All members of a list lines must begin with some indentation level starting with space.

  For example:

  --- # A list of fruits
  Fruits:
  - Mango
  - Strawberry
  - Banana
  - Grapes
  - Apple
  ...
  

• A dictionary is represented in a simple key-value pair.

  For example:

  --- # Details of customer
  Customer:
    Name: Bilal
    Job: YouTuber
    Skills: DevOps
    Exp: 1 year
  ...
  

  Note: There should be space b/w : and the value.

Target section

Steps

• Start the instances, connect the ansible server with node by using ssh -i <file-name.pem> ec2-user@<public-ip-address>.

• After that, go to ansible server by typing su - ansible.

• Create a YAML file by the name of target.yml and write the following data in it.

  --- # Target Playbook
  - hosts: groupname
    user: ansible
    become: yes
    connection: ssh
    gather_facts: yes
  ...
  

• become: yes means to give the sudo privilege.

• gather_facts: yes will gather the private ip addresses of the nodes.

• Execute the file by writing ansible-playbook target.yml

• To check the idempotency, execute the above command, and this will show the changed=0 because the task is not repeated.

Task section

Steps

• Create a YAML file by the name of task.yml and write the following data in it.

  --- # Task Playbook
  - hosts: groupname
    user: ansible
    become: yes
    connection: ssh
    gather_facts: yes
  
    tasks:
      - name: Install httpd on Linux
        action: yum name=httpd state=installed
  ...
  

• yum is the module name.

• You can also write present as a state that will install a package.

• Before executing a file, first remove the httpd package from all the nodes by typing sudo yum remove httpd -y.

• Execute the file by writing ansible-playbook task.yml and it will show you changed=1 because something new is added.

• After executing a file, type which httpd in all the nodes to confirm the installation.

Variables section

• Ansible uses variables which are defined previously to enable more flexibility in playbooks and roles. They can be used to loop through a set of given values, access various information like the host name of a system and replace certain strings in templates with specific values.

• Put variable section above tasks so that we define it first and use it later.

Steps

• Go to ansible server and switch to ansible user.

• Create a YAML file by the name of vars.yml and write the following data in it.

  --- # Variables Playbook
  - hosts: groupname
    user: ansible
    become: yes
    connection: ssh
    gather_facts: yes
  
    vars:
      - pkgname: httpd    
    tasks:
      - name: Install httpd on Linux
        action: yum name='{{pkgname}}' state=installed
  ...
  

• Before executing a file, first remove the httpd package from all the nodes by typing sudo yum remove httpd -y.

• Execute the file by writing ansible-playbook vars.yml

• After executing a file, type which httpd in all the nodes to confirm the installation.

Handlers Section

• A handler is exactly the same as a task but it will run when it is called by another task.

• The first task will be executed and then it will be shifted to another task. Without the first task completion, the second task won't complete.

• The first task must contain the notify directive to indicate and also notify that it changed something.

Steps

• Go to ansible server and switch to ansible user.

• Create a YAML file by the name of handlers.yml and write the following data in it.

  --- # Handlers Playbook
  - hosts: groupname
    user: ansible
    become: yes
    connection: ssh  
    tasks:
      - name: Install httpd server
        action: yum name=httpd state=installed
        notify: restart HTTPD
    handlers:
      - name: restart HTTPD
        action: service name=httpd state=restarted
  ...
  

• handlers value must be equal to notify value so that the handlers will run only after the task is completed.

• Before executing a file, first remove the httpd package from all the nodes by typing sudo yum remove httpd -y.

• Dry run: Check whether the playbook is formatted correctly before an execution by typing ansible-playbook handlers.yml --check.

• Execute the file by writing ansible-playbook handlers.yml.

• After executing a file, type which httpd in all the nodes to confirm the installation.

• For checking the status, write sudo service httpd status in all the nodes. If it is active then it means the httpd is running.

Loops

• Sometimes you want to repeat a task multiple times. In computer programming, this is called loops.

• Common ansible loops include changing ownership on several files and/or directories with the file module, creating multiple users with the user module, and repeating a pulling step until certain results are reached.

Steps

• Go to ansible server and switch to ansible user.

• Create a YAML file by the name of loops.yml and write the following data in it.

  --- # Loops Playbook
  - hosts: groupname
    user: ansible
    become: yes
    connection: ssh  
    tasks:
      - name: Add a list of users in the nodes
        user: name='{{item}}' state=present
        with_items:
          - Bilal
          - Ali_ahmed
          - Zeeshan
          - Rahmat
  ...
  

• It will go inside the node1 of a groupname and create the users one after the other. Then it will go to node2 of a groupname and create the users one after the other.

• The username should be written without a space, otherwise it will us an error.

• Execute the file by writing ansible-playbook loops.yml.

• To verify, go inside any node and type cat /etc/passwd.

Explaining it in a video

Here you can get an explanation in a video. 45/60 Day of DevOps Challenge