Ansible Playbooks are automated scripts written in YAML data format. Instead of using manual commands to setup multiple remote machines, you can utilize Ansible Playbooks to configure your entire systems. YAML syntax is easy to read and express the data structure of certain Ansible functions. You simply write some tasks, for example, installing software, configuring default settings, and starting the software, in a Ansible Playbook. With a few examples in this tutorial, you will understand how it works and how to write your own Playbooks.
Note
There are also several examples of using Ansible Playbooks from the official site. It covers from basic usage of Ansible Playbooks to advanced usage such as applying patches and updates with different roles and groups.
In this tutorial, we are going to write a basic playbook of Ansible software.
Keep in mind that Ansible is a main program and playbook is a template
that you would like to use. You may have several playbooks in your Ansible.
As a first example, we are going to write a playbook which installs MongoDB server. It includes the following tasks:
Note
This tutorial is based on the manual installation of MongoDB from the official site: http://docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/*
We also assume that we install MongoDB on Ubuntu 15.10.
Some setups of managed nodes may not allow you to log in as root. As
this may be problematic later, let us create a playbook to resolve
this. Create a enable-root-access.yaml file with the following
contents:
---
- hosts: ansible-test
remote_user: ubuntu
tasks:
- name: Enable root login
shell: sudo cp ~/.ssh/authorized_keys /root/.ssh/
Explanation:
hosts specifies the name of a group of machines in the inventoryremote_user specifies the username on the managed nodes to log in astasks is a list of tasks to accomplish having a name (a
description) and modules to execute. In this case we use the
shell module.We can run this playbook like so:
$ ansible-playbook -i inventory.txt -c ssh enable-root-access.yaml
PLAY [ansible-test] ***********************************************************
GATHERING FACTS ***************************************************************
ok: [10.23.2.105]
ok: [10.23.2.104]
TASK: [Enable root login] *****************************************************
changed: [10.23.2.104]
changed: [10.23.2.105]
PLAY RECAP ********************************************************************
10.23.2.104 : ok=2 changed=1 unreachable=0 failed=0
10.23.2.105 : ok=2 changed=1 unreachable=0 failed=0
First step is choosing hosts to install MongoDB and a user account to run
commands (tasks). We start with the following lines in the example filename of
mongodb.yaml:
---
- hosts: ansible-test
remote_user: root
become: yes
In a previous tutorial, we setup two machines with ansible-test group name.
This tutorial uses that two machines for MongoDB installation. Also, we use
root account to complete Ansible tasks.
Important
Indentation is important in YAML format. Do not ignore spaces start with in each line.
A list of tasks contains commands or configurations to be executed on remote
machines in a sequential order. Each task comes with a name and a
module to run your command or configuration. You provide a description of
your task in name section and choose a module for your task. There are
several modules that you can use, for example, shell module simply executes
a command without considering a return value. You may use apt or yum
module which is one of the packaging modules to install software. You can find
an entire list of modules here:
http://docs.ansible.com/list_of_all_modules.html
apt_key: add repository keys¶We need to import the MongoDB public GPG Key. This is going to be a first task in our playbook.:
tasks:
- name: Import the public key used by the package management system
apt_key: keyserver=hkp://keyserver.ubuntu.com:80 id=7F0CEB10 state=present
apt_repository: add repositories¶Next add the MongoDB repository to apt:
- name: Add MongoDB repository
apt_repository: repo='deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' state=present
apt: install packages¶We use apt module to install mongodb-org package.
notify action is added to start mongod after the completion of this task.
Use the update_cache=yes option to reload the local package database.:
- name: install mongodb
apt: pkg=mongodb-org state=latest update_cache=yes
notify:
- start mongodb
service: manage services¶We use handlers here to start or restart services. It is similar to
tasks but will run only once.:
handlers:
- name: start mongodb
service: name=mongod state=started
Our first playbook looks like this:
---
- hosts: ansible-test
remote_user: root
become: yes
tasks:
- name: Import the public key used by the package management system
apt_key: keyserver=hkp://keyserver.ubuntu.com:80 id=7F0CEB10 state=present
- name: Add MongoDB repository
apt_repository: repo='deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' state=present
- name: install mongodb
apt: pkg=mongodb-org state=latest update_cache=yes
notify:
- start mongodb
handlers:
- name: start mongodb
service: name=mongod state=started
We use ansible-playbook command to run our playbook:
$ ansible-playbook -i inventory.txt -c ssh mongodb.yaml
PLAY [ansible-test] ***********************************************************
GATHERING FACTS ***************************************************************
ok: [10.23.2.104]
ok: [10.23.2.105]
TASK: [Import the public key used by the package management system] ***********
changed: [10.23.2.104]
changed: [10.23.2.105]
TASK: [Add MongoDB repository] ************************************************
changed: [10.23.2.104]
changed: [10.23.2.105]
TASK: [install mongodb] *******************************************************
changed: [10.23.2.104]
changed: [10.23.2.105]
NOTIFIED: [start mongodb] *****************************************************
ok: [10.23.2.105]
ok: [10.23.2.104]
PLAY RECAP ********************************************************************
10.23.2.104 : ok=5 changed=3 unreachable=0 failed=0
10.23.2.105 : ok=5 changed=3 unreachable=0 failed=0
Note
If you rerun the playbook, you should see that nothing changed:
$ ansible-playbook -i inventory.txt -c ssh mongodb.yaml
PLAY [ansible-test] ***********************************************************
GATHERING FACTS ***************************************************************
ok: [10.23.2.105]
ok: [10.23.2.104]
TASK: [Import the public key used by the package management system] ***********
ok: [10.23.2.104]
ok: [10.23.2.105]
TASK: [Add MongoDB repository] ************************************************
ok: [10.23.2.104]
ok: [10.23.2.105]
TASK: [install mongodb] *******************************************************
ok: [10.23.2.105]
ok: [10.23.2.104]
PLAY RECAP ********************************************************************
10.23.2.104 : ok=4 changed=0 unreachable=0 failed=0
10.23.2.105 : ok=4 changed=0 unreachable=0 failed=0
Let’s try to run ‘mongo’ to enter mongodb shell.:
$ ssh ubuntu@$IP
$ mongo
MongoDB shell version: 2.6.9
connecting to: test
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
http://docs.mongodb.org/
Questions? Try the support group
http://groups.google.com/group/mongodb-user
>
The main tutorial from Ansible is here: http://docs.ansible.com/playbooks_intro.html
You can also find an index of the ansible modules here: http://docs.ansible.com/modules_by_category.html