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Lab 002 - No inventory example¶

• Lab 002 - No inventory example
  • 01. “Clear” the inventory
  • 01.01. Create the inventory file
  • Ansible Inventory
  • Key features of Ansible inventory
  • inventory types in Ansible
• Lab
  • 01. No inventory invocation
  • 02. inventory invocation

01. “Clear” the inventory¶

• Lets clear the inventory from previous steps and walk thorough what is inventory

01.01. Create the inventory file¶

Ansible Inventory¶

• An Ansible inventory is a file or collection of files that defines the [hosts] and [groups] of hosts upon which Ansible will operates.
• It’s simply a list of servers that Ansible can connect to and manage.

Key features of Ansible inventory¶

• Can be in various formats, with INI, JSON, YAML and more.
• YAML is the most common format
• inventory defines the target hosts for playbook execution
• inventory organizes hosts into logical groups for easier management
• inventory can store host-specific variables and group variables

• inventory supports nested groups (groups of groups)

  inventory samples¶

  • INI format

    [webservers]
    web1.example.com
    web2.example.com
    
    [database]
    db1.example.com
    

  • YAML format

    all:
        hosts:
            web1.example.com:
            web2.example.com:
        children:
            database:
            hosts:
                db1.example.com:
    

  • JSON format

    {
    "all": {
        "hosts": {
        "web1.example.com": {
            "ansible_port": 2222,
            "http_port": 80
        },
        "web2.example.com": {
            "ansible_port": 2223,
            "http_port": 8080
        }
        },
        "children": {
        "database": {
            "hosts": [
            "db1.example.com"
            ]
          }
        }
      }
    }
    

inventory types in Ansible¶

1. Static Inventory

   • This is generally a simple text file (usually in INI or YAML format) that lists your hosts and their corresponding groups.

2. Dynamic Inventory

   • This is generated by a script or a program that retrieves host information from an external source, such as cloud providers (like AWS, Azure, etc.), LDAP, or a database.

   • This allows for real-time updates and adaptability as environments change.

     • Example of generating Dynamic inventory using python code fetching data form datable

       #!/usr/bin/env python
       import sqlite3
       import json
       
       def get_inventory():
           conn = sqlite3.connect('servers.db')
           cursor = conn.cursor()
       
           cursor.execute('SELECT hostname, group_name, ansible_user FROM servers')
           rows = cursor.fetchall()
       
           inventory = {'all': {'hosts': [], 'vars': {}}}
       
           for row in rows:
               hostname, group_name, ansible_user = row
       
               if group_name not in inventory:
                   inventory[group_name] = {'hosts': [], 'vars': {}}
       
               inventory['all']['hosts'].append(hostname)
               inventory[group_name]['hosts'].append(hostname)
               inventory[group_name]['vars']['ansible_user'] = ansible_user
       
           conn.close()
           return inventory
       
       if __name__ == "__main__":
           print(json.dumps(get_inventory()))
       

Lab¶

• Lets create the inventory configuration we will use for the labs:

  ### File Location: $RUNTIME_FOLDER/labs-scripts/inventory
  ###
  ### List of servers which we want ansible to connect to
  ### The names are defined in the docker-compose
  ###
  
  [servers]
  # No server will be defined at this step
  

01. No inventory invocation¶

• Once all is ready lets check is the controller can connect to the servers with the using ping

  # Ping the servers and check that they are "alive"
  docker exec ansible-controller sh -c "cd /labs-scripts && ansible all -m ping"
  
  ## Output
  ## -------------------------------------------------------------------------------
  [WARNING]: provided hosts list is empty, only localhost is available. Note that
  the implicit localhost does not match 'all'
  

02. inventory invocation¶

• Fill in the inventory based upon the prevoius labs configuration and test it.
• Verify that the inventory is defined correctly with:

  ansible-inventory -i <inventory_file> --graph
  

• Test the inventory file with

  ansible -i <inventory_file> -m ping
  

• Suggested Solution

  ###
  ### List of servers which we want ansible to connect to
  ### The names are defined in the docker-compose
  ###
  
  [servers]
    linux-server-1 ansible_ssh_common_args='-o UserKnownHostsFile=/root/.ssh/known_hosts'
    linux-server-2 ansible_ssh_common_args='-o UserKnownHostsFile=/root/.ssh/known_hosts'
    linux-server-3 ansible_ssh_common_args='-o UserKnownHostsFile=/root/.ssh/known_hosts'
  

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