DevOps Classroom Series – 11/Aug/2020

Ansible Behavior Inventory Parameters

• Refer Here for official docs
• Some Inventory Parameters
  • ansible_host: This will be host name or ipaddress which ypu can set to the host
    • Consider this inventory file

    myfavoriteserver ansible_host="172.31.4.122"
    yourfavoriteserver.com ansible_host="localhost"
    

    • Now lets run simple ansible ping adhoc command ansible -i hosts -m ping all
  • ansible_port: Specifies the port number that Ansible will use to connect to inventory host, Sample inventory

  localhost ansible_port=8922
  

  • ansible_user: Specifies the username that ansible will connect to the inventory host.
  • ansible_ssh_pass: Used to provide the ssh password to authenticate with inventory host.

  192.168.10.23 ansible_user="admin" ansible_ssh_pass="admin123"
  

  • ansible_ssh_private_key_file: Used to specify the SSH private key file to connect to inventory host

  34.25.15.14 ansible_user="ec2_user" ansible_ssh_private_key_file="./ansible.pem"
  

  • ansible_ssh_common_args: This defines ssh arguments to append to default arguments for ssh, sftp and scp
  • ansible_sftp_extra_args: Used to specify additional sftp arguments
  • ansible_scp_extra_args: Used to specify additional scp arguments
  • ansible_ssh_extra_args: Used to specify additional ssh arguments
  • ansible_ssh_executable:
  • ansible_become: This defines whether privilege escalation(sudo or otherwise) should be with this host
  • ansible_become_method: Which method to use for privilege and can be one of sudo, su, pfexec,doas,dzdo,pbrun or ksu
  • ansible_become_user: This is user to become through privilege escalation
  • ansible_become_pass: This is password for become user.
  • ansible_sudo_pass: This is sudo password to use
  • ansible_connection: This is the connection type of the host. values are one of ssh,local,smart,docker, paramiko or winrm. Default is smart
  • ansible_docker_extra_args:
  • ansible_shell_type: Default shell of the inventory host
  • ansible_shell_executable: Default shell types executable
  • ansible_python_interpreter: This is used to manually set the path of python interpreter on a given host in the inventory
    • Consider the below inventory

    [python3]
    172.31.3.192 ansible_python_interpreter="/usr/bin/python3"
    [python2]
    localhost
    

    • Now run simple adhoc command “`ansible -i diffpythonhosts -m ping all

Inventory Limiting

• Consider the following inventory

[webserver]
172.31.3.192 ansible_python_interpreter="/usr/bin/python3"
172.31.4.122

[local]
localhost

• Now we have written a playbook or adhoc command for

ansible -m ping all

• Playbook is

---
- name: just fun
  hosts: all
  tasks:
    - name: ping host
      ping:
    - name: print host
      debug:
        var: inventory_host

• Now executing this playbook will result as shown below
• Now we can supply –limit as shown below

Ansible Variables in separate files

• Rather than writing variable data in inventory, it is a best practice to write them separately in a file, for that we need to understand how to create files for group variables and host variables
• Lets assume this inventory and create it in a file called as hosts

[webservers]
172.31.4.122
172.31.3.192

[dbservers]
localhost

• Now the following playbook is created

---
- name: just fun
  hosts: all
  tasks:
    - name: ping host
      ping:
    - name: print host
      debug:
        var: inventory_hostname
    - name: print variable
      debug:
        var: from_where

• Lets add the following entries in group_vars/webservers.yaml

---
from_where: group_webservers

• In group_vars/dbservers.yaml

---
from_where: group_dbservers

• In host_vars/172.31.3.192.yaml

---
ansible_python_interpreter: "/usr/bin/python3"
from_where: hosts_172.31.3.192

• Lets look at folder structure
• The convention is in the folder wherever you have inventory in the same folder create folder named "group_vars" and the file name will be group_vars/<groupname>.yaml. Similarly for host variable the file names will be host_vars/<hostname>.yaml
• lets execute playbook

Next Steps

• Steps while parsing playbooks
• Order of operations
• Play behavior directives
• Execution strategies