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Ansible Rough Guide

_static/zebraffe.png

Description

Ansible is a DevOps tool. Its actions are called Plays and groups of those actions are called Playbooks. Ansible is designed to be easy to install, implement and use.

Prerequisites

  • Linux
  • Python 2.7
  • Ansible

Setup

Once you setup your server with the ansible software (its CLI driven), you simply make sure you can SSH into your target hosts. You can Setup SSH passphrases if you like, but it works regardless. You can also run on non-standard (non-22) tcp port numbers.

Inventory

You define your managed hosts with Inventory Files.

# ------------------------------------------------------------------
# file: production

[monitors]
mp1.zenoss.loc
mp2.zenoss.loc  ansible_ssh_port=2201 ansible_ssh_host=90.14.17.12

[locals]
localhost              ansible_connection=local

Group Vars and Host Vars

Group and Host vars are simple YAML files. From your ansible root, they are located in:

$ANSIBLE/group_vars
$ANSIBLE/host_vars

An example of group and host vars:

[joe@zen:~/ansible]: cat group_vars/all
# ================= Ansible Group Vars: ALL ========================
---
# Variables listed here are applicable to all host groups

http_port: 80
https_port: 443
ntpserver: us.pool.ntp.org
git_repo: http://github.com/xxx/mywebapp.git
sudo_user: joe
opt_bin: /opt/bin
opt_log: /opt/log
maven_url: http://www.eng.lsu.edu/3.0/binaries/apache-maven-3.0.5-bin.tar.gz

and some host vars....

[joe@zen:~/ansible]: cat host_vars/mp1.zenoss.loc
backup_tools:
  - backup_files
  - backup_home
  - disk_backup_dirvish
  - find_duplicates
  - report_df
  - reset_cronlog
  - restart_apcmon
  - sudo_dirvish
  - rsync-new

dirvish_master: False

hourly_jobs:
 - check_raid
 - check_space

daily_jobs: []

Playbooks

Playbooks contain the commands that configure the targets. A playbook is YAML file that has some commands in it. It can be simply a bunch of commands in a single file or group of files.

Each section is YAML and is indented by 2 at each level. A simple example is:

# A very simple example for a CentOS box
---
- name: Ensure needed packages are the latest version
  yum: pkg={{item}} state=latest
  with_items:
    - lxc
    - make
    - icewm
    - openbox

Roles: Getting Organized

Roles allow you to organize your tasks. A Roles folder lives in the Ansible root and has a series of folders that correspond to task groups:

ansible
|
|-- group_vars
|   \-- all
|-- host_vars
|   |-- 192.168.122.7
|   \-- mp2.zenoss.loc
|-- laptops.yml
|-- production
|-- roles
|   |-- common
|   |-- network
|   |-- security
|   \-- zenoss
\-- zenoss.yml

Inside of each role are the following directories which ansible will automatically search for needed files:

[joe@zenpad:~/ansible]: tree -L 1 roles/security
ansible/roles/security/
|-- files
|-- handlers
|-- tasks
|-- templates
\-- vars

Here is the lowdown on what goes in these folders:

  • files: Just plain old files for copy
  • handlers: plays that get triggered by a notify event
  • tasks: the big enchilada play
  • templates: files that get templated
  • vars: any vars local to the role

So full blown security folder looks like this:

[joe@zenpad:~/ansible]: tree -L 5 roles/network
roles/network/
|-- files
|-- handlers
|   |-- main.yml
|-- tasks
|   |-- centos.yml
|   |-- debian.yml
|   |-- main.yml
|   |-- ubuntu.yml
|-- templates
|   |-- ifcfg-eth0
|   |-- ifcfg-eth2
|   |-- ifcfg-static
|   |-- network
|   \-- sysconfig
|       \-- network-scripts
\- vars

Thats enough theory. Lets do some demonstrations!

Links: