Overview

This lab is based on the Udemy course https://www.udemy.com/mastering-ansible/ The lab has been built with Virtualbox VM host, and may not work with other VM providers without modification. This lab does not use Ansible via Vagrant, and thus Ansible is not a requirement on your Vagrant host. Ansible will be installed on an ansible host VM, and all playbooks to configure the lab machines will be run from there interactively, once Vagrant has built the base VMs. The lab configures a simple nginx load balancer, 2 web app servers and a mysql database.

The lab will implement the following configuration:

Machine Name	Role	Network Configuration	OS
control	Ansible host	private_network, ip: 192.168.135.10	Ubuntu Trusty64 (14 LTS)
lb01	Load Balancer	private_network, ip: 192.168.135.101	Ubuntu Trusty64 (14 LTS)
app01	web server 1	private_network, ip: 192.168.135.111	Ubuntu Trusty64 (14 LTS)
app02	web server 2	private_network, ip: 192.168.135.112	Ubuntu Trusty64 (14 LTS)
db01	mysql db	private_network, ip: 192.168.135.121	Ubuntu Trusty64 (14 LTS)

Quick Start

• Clone this repo
• Install the hostmanager Vagrant plugin if ytou haven't already vagrant plugin install vagrant-hostmanager
  • on a Mac Vagrant host, brew install libffi was required prior to installing the plugin successfully
• run vagrant up from the root of the synced repo (the folder with Vagrantfile in it)
• Once the VMs are built, type vagrant ssh control to logon to the ansible controller from within your vagrant project folder
• Change directories cd /vagrant/ansible which is the ansible subfolder of your vagrant project for this lab (the vagrant project folder is mounted within the VMs as /vagrant during provisioning)
• run ansible-playbook playbooks/site.yml to build the entire 3 tier configuration (load balancer, sample web app, and database connection)
• run ansible-playbook playbooks/stack_status.yml to validate status of each component
• test that the application stack is working properly end to end by running curl http://lb01/db

#Exploring the details

• ./hosts
  • file defining the servers to be orchestrated
• ./ansible.cfg
  • defines hosts file location and ansible vault password file location
• ./group_vars/all/vars
  • global variables file, includes database name and login user info
• ./group_vars/all/vault
  • file encrypted containing database user password (vault_db_pass)
  • you can view and edit the file with ansible-vault edit group_vars/all/vault - your decryption key specified in ansible.cfg will be used to decrypt and reencrypt the file transparently
• ./site.yml - main playbook wrapper, which includes playbooks for the various server types, such as loadbalancer.yml, for building the front end load balancer
• ./loadbalancer.yml
• defines affected hosts ("loadbalancer", which in turn is a group defined in ./hosts file)
• references the role of type nginx, which means to include running the playbook in playbooks/roles/tasks/main.yml
• (same idea for database.yml, control.yml, webserver.yml)
• ./playbooks/roles/nginx (same concept for each role in playbooks/roles/*)
  • ./playbooks/roles/nginx/defaults/main.yml variable defaults
  • ./playbooks/roles/nginx/vars/main.yml variables, if defined here would override the ones in defaults folder
  • ./playbooks/roles/nginx/handlers/main.yml handler definitions for "notify" actions in tasks
  • ./playbooks/roles/nginx/tasks/main.yml task step definitions
  • ./playbooks/roles/nginx/templates/nginx.conf.j2 config file template, used in the "configure nginx site" step in tasks/main.yml, using the "template:" module to customize the .j2 file template into nginx.conf

Ansible syntax samples

##Selecting and filtering hosts to work with

#####selecting hosts ansible --list-hosts all ansible --list-hosts "*"

####name of group in hosts file ansible --list-hosts loadbalancer

####wildcard filter ansible --list-hosts "app*"

####multiple groups separated by a colon (deprecated) ansible --list-hosts database:control

####multiple groups separated by a comma ansible --list-hosts database,control

####select first node in webserver group ansible --list-hosts webserver[0]

####everything not in control group, bang escaped in bash ansible --list-hosts !control

##simple commands

####internal ping module ansible -m ping all

####command module (-m) executing "hostname" command (-a) ansible -m command -a "hostname" all

####command with just -a is equiv, as command module is default module ansible -a "hostname" all

####show what hosts are involved in this playbook ansible-playbook playbooks/site.yml --list-hosts

####show what tags are involved in this playbook ansible-playbook playbooks/site.yml --list-tags

using playbooks

####simple playbook that executes "hostame" command ansible-playbook /vagrant/playbooks/hostname.yml

####run only steps in a playbook that have a tag called "packages" defined ansible-playbook playbooks/site.yml --tags "packages"

####run only steps in a playbook that DON'T have a tag called "packages" defined ansible-playbook playbooks/site.yml --skip-tags "packages"

####step through tasks and be prompted whether to run each step or not ansible-playbook playbooks/site.yml --step

####show all tasks that will be executed by the playbook ansible-playbook playbooks/site.yml --list-tasks

####skip over steps in a playbook and start at a specific task ansible-playbook playbooks/stack_status.yml --start-at-task "verify end-to-end response"

####verify syntax ansible-playbook --syntax-check playbooks/site.yml

####do a simulated run of the playbook ansible-playbook --check playbooks/site.yml

##Utilities

gather facts available

ansible -m setup all