Basic Commands of Ansible

In Lab 6: Basic Commands of Ansible, participants typically delve into the fundamental commands and concepts that form the core of Ansible's automation capabilities. This lab focuses on hands-on experience with commands such as 'ansible' to execute ad-hoc commands on remote hosts, 'ansible-playbook' to run playbook scripts, and 'ansible-galaxy' to manage roles. Participants may also explore concepts like inventories, which define the target hosts, and modules, which represent individual tasks within playbooks. The lab aims to deepen participants' understanding of Ansible's syntax and workflow, empowering them to automate repetitive tasks, configurations, and deployments effectively. Successful completion of Lab 6 equips participants with the foundational skills needed to harness Ansible's automation power for streamlined infrastructure management within their DevOps environments.

Lab:

Host Patterns

vi /etc/ansible/hosts

//“all” pattern referes to all the machines in an inventory
ansible all --list-hosts
ansible <group name> --list-hosts
ansible <group name>\[0\] --list-hosts

//You can refer to hosts within the group by adding a subscript to the group name while giving the pattern
Groupname\[0\]  -> Picks the first machine in the group
Groupname\[1\]  -> Picks the second machine in the group
Groupname\[-1\] -> Picks the last machine in the group
Groupname\[0:1\] -> Picks first 2 machine in the group

//Group separated by colon can be used to use hosts from multiple groups
Groupname1:groupname2

Ansible ad-hoc commands

• Use of ad-hoc tasks really quick and don’t want to save for later
• These are quick one-liner without writing a playbook
• To run an arbitrary command use (-a)

ansible all --list-hosts
ansible demo –a “ls”
ansible demo –a “ls-al”
ansible demo –a “touch myfile” (re run and verify idempotence)
ansible demo –a “yum install httpd –y” (shows permission denied)

• To run anything with sudo, use –b

ansible demo –b –a “yum install httpd –y”
ansible demo –b –a “yum remove httpd –y” 

Ansible Modules

• To run an arbitrary cmd use –a & use –m to run a module

ansible \[group\] –m <module> -z <cmd>
ansible demo –m ping
ansible demo –b –m yum –a “pkg=httpd state=present”
ansible demo –b –m yum –a “pkg=httpd state=latest”
ansible demo –b –m yum –a “pkg=httpd state=absent”

// State=present will install it
// State=latest will update
//State=absent will remove it

• Start/Stop a service

ansible demo –b –m service –a “name=httpd state=started”
ansible demo –b –m service –a “name=httpd state=restarted”
ansible demo –b –m service –a “name=httpd state=stopped”

• Create/Delete a user account

ansible demo –b –m user –a “name=raj”
ansible demo –b –m user –a “name=raj state=absent”

• Gathering facts (Idempotence)

ansible demo –m setup
ansible demo –m setup –a ‘filter=\*ipv4\*’

Playbooks

• Playbook is like a file where you write code. Playbooks are expressed in YAML format

ansible-playbook <playbook>.yml

• For Ansible, nearly every YAML file starts with a list
• Each item in the list is a list of key/value pairs, commonly called a “dictionary”
• All YAML files have to begin with “—” and end with “ —”
• All members of a list lines must begin with same indentation level starting with “-”

\---# A list of tasty fruits
fruits:
  - Apple
  - Orange
  - Straberry
  - Mango
---

• A dictionary is represented in a simple key:value form

\---#An employee record
Employee:
  name: Ram
  job: DevOps Engineer
  skill: Elite
---