5. Ansible : Introduction
Where is the problem ?
Scripts are :
● Hard to maintain
● Boring in heterogeneous environments
● Not idempotent natively
I hope: centralized, versioned, documented, easy to read for a new colleague
An idempotent operation is one that has no additional effect if it is called more than once with the same input parameters
*
7. Ansible : Introduction
What's a provisioning framework?
● Automated setup of servers
● Configuration as code
Create users
Install software
Generate and manipulate
config files
Start/stop/restart
processes
Set up dependencies
between operations
9. Ansible
● Ansible is based on Python
● Standard SSH to connect to managed servers/nodes
● Push-based system
● Agentless operation
● No central server, no special software on managed nodes
● Facts from each node used for state-full decisions
● Idempotent ConfigMgmt tool (like others)
● Extend with custom modules, use any language which can return JSON
● Inventory from various datasource, return as JSON
An idempotent operation is one that has no additional effect if it is called more than once with the same input parameters
10. Ansible
● Ansible is similar to Chef, Puppet or Salt
● Shared purpose – solve tasks for CfgMgmt, provisioning, deployment, etc.
● Ansible may be simplest and easiest configuration management tool to start
● Chef, Puppet, Salt are great tools as well, may be more complex to start with, steeper
learning curve, etc.
● The absence of an agent allows it to manage more than servers (network or storage
equipment)
● It supports managing major cloud devices (AWS, RackSpace, Digital Ocean,
OpenStack) through a collection of modules which are available
11. Ansible
LAB
Setup
● Install VirtualBox & Vagrant
● Clone the repository on github
– git clone https://github.com/cdelgehier/oktocampus_ansible.git
● Run the Vagrantfile
– vagrant up (or vagrant up bastion prod1 prod2 for poor laptop)
● Connect you to your own bastion
– vagrant ssh bastion
● Generate your ssh key
– ssh-keygen -t rsa -b 2048
● Accept host ssh key file
– ssh-keyscan prod1 prod2 rec1 rec2 > ~/.ssh/known_hosts
README.md
12. Ansible : Ad Hoc mode
● You don't have to create an elaborate set of tasks just to perform simple operations
on your nodes
● An ad-hoc command consists of two parameters; the host group that defines on what
machines to run the task against and the Ansible module to run
ansible <group> -m <module>
$> ansible prod -m ping
$> ansible prod -m command -a 'whoami'
$> ansible prod -m setup
$> ansible prod -a 'hostnamectl'
-m command is by default
$> ansible all -a '/sbin/reboot' --forks=10
$> ansible recette -m user -a 'name=georges password=okto'
$> ansible alll -m yum -a 'name=nginx state=installed'
$> ansible alll -m service -a 'name=nginx state=started'
$> ansible all –list-hosts
$> ansible localhost -m debug -a 'var=groups.keys()'
13. Ansible
LAB
Part 1
In Ad Hoc only and with the manual
http://docs.ansible.com/ansible/list_of_all_modules.html
or with the ansible-doc commande
Try :
● To install a package (with yum) named epel-release then another named cowsay
● To run the command coway with moooo in argument
● Try add a user john which one is a member of the okto group
● Create a gzip archive of /etc/shadow into /tmp
14. Ansible
LAB
Part 1
● ansible all --become --module-name yum --args "name=epel-release state=present"
● ansible all -b -m yum -a "name=cowsay state=present"
● ansible all -a "cowsay moooo"
● ansible all -b -m group -a "name=okto"
● ansible all -b -m user -a "name=john group=okto"
● ansible all -b -m archive -a "path=/etc/shadow dest=/tmp/shadow.gz"
17. Ansible : concepts
● Modules : accomplish dedicated Tasks (set values, use templates)
● Tasks : execute Module specific parameters, variables, etc.
● Variables : configuration-wide, Playbook/Roles specific vars
● Facts : gather information about the target system
● Handlers : like Tasks but usually get called by another Task
● Roles : group related Tasks, encapsulate data to accomplish Task
● Files : files directory contains files copied over to target
● Templates : Jinja2 format with placeholders to insert variables
● Vault : encrypt sensible data
● Plays : are lists of Tasks wich apply to hosts / host groups
● Playbooks : YAML formatted files orchestrate steps sequentially
● Inventory : a combination of a hosts and groups
20. Ansible : Playbooks
● YAML Files
● Declaratively define your configuration
● Can contain many « plays » targetting different
groups
Describe state (declarative)Describe what to do (imperative)
21. Ansible : Playbooks
---
- name : play 1
hosts: all
gather_facts: yes
become: yes
vars:
docroot: /var/www/html/
title: oktocampus
body: |
<h1>Hello all !</h1>
<p>Is there any pizza left ? :)</p>
tasks:
- name: install epel repo
tags: install
yum:
name: epel-release
state: present
- name: install apache httpd
tags: install
yum:
name: httpd
state: present
- name: start and enable httpd
tags: config
service:
name: httpd
state: started
enabled: yes
- name: install packages in loop
tags: install
yum:
name: "{{ item }}"
state: present
with_items:
- ca-certificates
- w3m
- name: templating of my awesome html file
tags: config
template:
src: index.html.j2
dest: "{{ docroot }}/index.html"
owner: apache
group: apache
roles:
- role: ntp
ntp_timezone: "Europe/Paris"
ntp_manage_config: true
ntp_area: "fr"
ntp_servers:
- "0.{{ ntp_area }}.pool.ntp.org iburst"
- "1.{{ ntp_area }}.pool.ntp.org iburst"
- "2.{{ ntp_area }}.pool.ntp.org iburst"
- "3.{{ ntp_area }}.pool.ntp.org iburst"
...
All YAML files can optionally begin with --- and end with ...
Define targets for this play
Ansible provides many facts about the system, automatically
This play needs a privilege escalation
Roles are played before tasks
Overwrite role's defaults
Module used
<!DOCTYPE html>
<html>
<head>
<title>{{ title }}</title>
</head>
<body>
{{ body }}
# generated on {{ ansible_hostname }} OS: {{ ansible_distribution }}
{{ ansible_distribution_major_version }} ip: {{ ansible_eth1.ipv4.address }}
</body>
</html>
22. Ansible : Roles
$> ansible-galaxy init ntp
$> tree ntp
ntp
|-- defaults
| `-- main.yml
|-- files
|-- handlers
| `-- main.yml
|-- meta
| `-- main.yml
|-- README.md
|-- tasks
| `-- main.yml
|-- templates
| |-- ntp.conf.j2
| `-- timezone.j2
|-- tests
| |-- inventory
| `-- test.yml
`-- vars
|-- Debian.yml
|-- FreeBSD.yml
|-- main.yml
`-- RedHat.yml
Creation of a role folder
Variables customizable by the user
Variables specific to the role
Set of tests
---
- name: include distribution or OS Family variable
include_vars: "{{ item }}"
with_first_found:
- "{{ ansible_distribution }}.yml"
- "{{ ansible_os_family }}.yml"
- name: Ensure NTP-related packages are installed.
tags: install
package:
name: "{{ item }}"
state: present
with_items:
- ntp
- tzdata
- name: Set timezone
tags: config
timezone:
name: "{{ ntp_timezone }}"
- name: Ensure NTP is running and enabled as configured.
tags: config
service:
name: "{{ ntp_daemon }}"
state: started
enabled: yes
when: ntp_enabled
- name: Ensure NTP is stopped and disabled as configured.
tags: config
service:
name: "{{ ntp_daemon }}"
state: stopped
enabled: no
when: not ntp_enabled
- name: Generate ntp.conf file
tags: config
template:
src: ntp.conf.j2
dest: /etc/ntp.conf
notify: restart ntp
when: ntp_manage_config
...
---
ntp_enabled: true
ntp_timezone: "Etc/UTC"
ntp_manage_config: false
ntp_area: ""
ntp_servers:
- "0.{{ ntp_area }}.pool.ntp.org iburst"
- "1.{{ ntp_area }}.pool.ntp.org iburst"
- "2.{{ ntp_area }}.pool.ntp.org iburst"
ntp_restrict:
- "127.0.0.1"
- "::1"
...
---
ntp_daemon: ntpd
...
---
ntp_daemon: ntp
...
23. Ansible : Best practices
● Create a consistency in :
– Tagging
– Naming of tasks|variables|plays|roles
– Enforce the style with a pre-commit hook
● Separate tags and playbooks that have the purpose of installing and
provisioning
● Prefix role variables with role name
● Use native YAML syntax for your plays: Vertical reading is easier
● Use the run command modules (shell/command/script/raw) as a last
resort
24. Ansible : Best practices
● Don’t just start services -- use sanity/smoke tests
● Consider writing a module when your play is full of shell module
● Consider writing a filter when jinja hinders the readibility
25. Ansible
LAB
Part 2
In a playbook only and with the manual
http://docs.ansible.com/ansible/list_of_all_modules.html
or with the ansible-doc commande
Try :
● To write a playbook which check if salt is in the uri http://locahost
● Same idea but the pattern have to be different for the groups [prod] and [recette]
26. Ansible
LAB
Part 2
$> cat site.yml
---
- name : play 1
hosts: all
gather_facts: yes
become: yes
#vars:
# pattern: salt
Tasks:
- name: Get content page
uri:
url: http://localhost
return_content: yes
register: webpage
- name: Fail if {{ pattern }} is not in the page content
fail:
msg: "No >>> {{ pattern }} <<< in this page"
when: "pattern not in webpage.content"
#when: "ansible_hostname not in webpage.content"
...
$> cat inventory
[prod]
prod1
prod2
[recette]
rec[1:2]
[prod:vars]
pattern=pizza
[recette:vars]
pattern=salt
27. Ansible : Security
● Ansible can use a vaulted variable that lives in
an otherwise ‘clear text’ YAML file.
This is useful on github/lab
28. Ansible : Docker for CI
● « Trust is the essential reason why we need
continuous integration. »
● With Docker and a CI tool, we can do checks
on each git commit on our roles
