Ansible introduction

#

Modules

#

• Command module: Takes the command and executes it
• Shell module: Executes through a shell like /bin/sh
• Script module: Runs a local script on a remote node after transferring it.
• raw: executes a ssh command. useful for installation python3

Adhoc commands

#

Examples:

• ansible all - ping
• ansible web -m command -a “uptime”
• ansible localhost -m setup

Static inventory

#

Sample inventory:

[control]
control ansible_host=10.42.0.2

[web]
node-1 ansible_host=10.42.0.6
node-2 ansible_host=10.42.0.7
node-3 ansible_host=10.42.8

[haproxy]
haproxy ansible_host=10.42.0.100

[all:vars]
ansible_user=vagrant
ansible_ssh_private_key_file=~/.vagrant.d/insecure_pvt_key

Test adhoc commands

#

• ansible all -i hosts.ini -u vagrant -m ping: to test if systems are up
• ansible all -i hosts.ini -u vagrant -m setup: to test if system is setup
• ansible webservers -i hosts -u vagrant -m yum -a “name=python36 state=present” -b: installing packages python. -a is for args for yum module, -b become root
• Ansible is idempotent
• ansible webservers -i hosts -u vagrant -m yum -a “name=python36 state=absent” -b: to remove python

Variables

#

Ansible can work with metadata from various sources and manage their context in the form of variable. Can be facts, filepaths, package versions, etc.

Variable precedence (ansible 2.x):

1. Extra vars
2. Task vars
3. Block vars
4. Role and include vars
5. Play vars_files
6. Play vars_prompt
7. Play vars
8. Set_facts
9. Registered vars
10. Host facts
11. Playbook host_vars
12. Playbook group_vars
13. Inventory host_vars
14. Inventory group_vars
15. Inventory vars
16. Role defaults

get_url: download an archive git: clone a source code repo

Tasks

#

Example tasks in a play

tasks:
  - name: add cache dir
    file:
      path: /opt/cache
      state: directory

  - name: install nginx
    yum:
      name: nginx
      state: latest

  - name: restart nginx
    service:
      name: nginx
      state: restarted

Handler Tasks

#

Handlers are special tasks that run at the end of the play if notified by another task (caused by change of state). If a configuration file gets changed notify a service restart it needs to run.

tasks:
  - name: add cache dir
    file:
      path: /opt/cache
      state: directory

  - name: install nginx
    yum:
      name: nginx
      state: latest
    notify: restart nginx

handlers:
  - name: restart nginx
    service:
      name: nginx
      state: restarted

Plays and Playbooks

#

Plays are ordered sets of taks to execute against host selections from your inventory. A playbook is a file containing one or more plays

Playbook example:

---
- name: install and start apache
  hosts: web
  vars:
    http_port:80
    max_clients: 200
  remote_user: root

  tasks:
  - name: install httpd
    yum: pkg=httpd state=latest
  - name: write the apache config file
    template: src=/srv/httpd.j2 dest=/etc/httpd.conf
  - name: start httpd
    service: name=httpd state=started

Playbook files

#

site.yml(or main.yml)

---
- name: install and start apache
  hosts: webservers
  remote_user: vagrant
  become: yes

  tasks:
  - name: install epel repo
    yum: name=epel-release state=present

  - name: install python bindings for SELinux
    yum: name={{item}} state=present
    with_items:
    - libselinux-python
    - libsemanage-python

  - name: test to see if SeLinux is running
    command: getenforce
    register: sestatus
    changed_when: false

  - name: install apache
    yum: name=httpd state=present

  - name: start apache
    service: name=httpd state=started enabled=yes

• ansible-playbook -i hosts site.yml: to run playbook (execute tasks from top to bottom)

Transition playbooks to roles

#

Roles are a packages of closely related ansible content that can be shared more easily than plays alone

Roles directory structure

#

• defaults:
• files:
• handlers:
• meta:
• molecule:
• tasks:
• templates:
• vars:

Creating a new role

#

• ansible-galaxy init –help
• ansible-galaxy init role_name
• meta: flush_handler: runs the handler right now

Running multiple roles in a playbook

#

Example:

---
- name: apply the common configuration to all hosts
  hosts: all
  remote_user: vagrant
  become: yes

  roles:
  - common

- name: apply the database configuration
  hosts: dbservers
  remote_user: vagrant 
  become: yes

  roles:
  - mariadb

- name: apply the apache and the web roles
  hosts: webservers
  remote_user: vagrant
  become: yes

  roles:
  - apache
  - web

- name: apply the lb configuration
  hosts: lbservers
  remote_user: vagrant
  become: yes

  roles: 
  - haproxy