CHAPTER 4: IMPLEMENTING PLAYBOOKS

Playbooks to run multiple, complex tasks against a set of targeted hosts in an easily repeatable manner.
A play is an ordered set of tasks which should be run against hosts selected from your inventory.
A playbook is a text file that contains a list of one or more plays to run in order.

 

Format of an Ansible Playbook 

name: just an example
hosts: webservers
tasks:
- first
- second
- third

Example play has three keys: name, hosts, and tasks. These keys all have the same indentation because they belong to the play.

Example shows the contents of a simple playbook, and then the result of running it.

Note : client machine is where we will install web server

[rootcontrolnode ]$ mkdir imp-playdemo

[rootcontrolnode imp-playdemo]$ vim webserver.yml

name: play to setup web server
hosts: client-machine.example.com
tasks:

 name: latest httpd version installed
 yum:
   name: httpd
   state: latest

[root@controlnode imp-playdemo]$ ansible-playbook webserver.yml

PLAY [play to setup web server] ************************************************
TASK [Gathering Facts] *********************************************************
ok: [servera.lab.example.com]
TASK [latest httpd version installed] ******************************************
changed: [servera.lab.example.com]
PLAY RECAP *********************************************************************
servera.lab.example.com
: ok=2
changed=1
unreachable=0
failed=0 

Syntax Verification : The ansible-playbook command offers a --syntax-check option which can be used to verify the syntax of a playbook file.

[root@controlnode ~]$ ansible-playbook --syntax-check webserver.yml 

playbook: webserver.yml

Executing a Dry Run : Another helpful option is the -C option. 

Note : This causes Ansible to report what changes would have occurred if the playbook were executed, but does not make any actual changes to managed
hosts. 

[root@controlnode ~]$ ansible-playbook -C webserver.yml

 Example : Install Apache package on client machine 

 A working directory, /home/root/basic-playbook, has been created on control server.

Step 1 :Need two server 

• I . Host server (client machine) IP- 192.168.103.101 
• II. Control Node
  

First check client machine is ping from Control machine.

[rootcontrol-node]$ping client.example.com
[root@control]$ mkdir inventory_dir
[root@control]$ cd inventory_dir
[root@control inventory_dir]$  vim inventory 

[webserver] 
192.168.103.101

Step 2: Configure ansible config file.

[root@control ~]$ mkdir /home/root/playbook
[root@control ~]$ cd /home/root/playbook
[root@control palybook]$ vim ansible.cfg
[defaults]
inventory=inventory

[rootcontrol-node]$mkdir /home/root/basic-playbook 
[rootcontrol-node]$cd  /home/root/basic-playbook
[rootcontrol-node playbook]$vim site.yml 

name: Install and start Apache HTTPD
hosts: web
tasks:
- name: httpd package is present
yum:
name: httpd
state: present
- name: correct index.html is present
copy:
src: files/index.html
dest: /var/www/html/index.html
- name: httpd is started
service:
name: httpd
state: started
enabled: true 

Save the file and exit your text editor. 

 

[root@basic-playbook]$ ansible-playbook --syntax-check site.yml

[root@basic-playbook]$ ansible-playbook site.yml 

 

PLAY [Install and start Apache HTTPD] ******************************************
TASK [Gathering Facts] *********************************************************
ok: [serverd.lab.example.com]
ok: [serverc.lab.example.com]
TASK [httpd package is present] ************************************************
changed: [serverd.lab.example.com]
changed: [serverc.lab.example.com]
TASK [correct index.html is present] *******************************************
changed: [serverd.lab.example.com]
changed: [serverc.lab.example.com]
TASK [httpd is started] ********************************************************
changed: [serverd.lab.example.com]
changed: [serverc.lab.example.com]
PLAY RECAP *********************************************************************
serverc.lab.example.com
: ok=4
changed=3
unreachable=0
failed=0
serverd.lab.example.com
: ok=4
changed=3
unreachable=0
failed=0

 

1. The httpd package is present, using the yum module. 

2. The local files/index.html file is copied to /var/www/html/index.html on each managed host, using the copy module.

3. The httpd service is started and enabled, using the service module.

Implementing Multiple Plays

A playbook is a YAML file containing a list of one or more plays.

The following example shows a simple playbook with two plays. 

The first play runs against web.example.com, and the second play runs against database.example.com.

Note :There is two server web server and database server for install database and Apache

# This is a simple playbook with two plays
[root@control]vim playbook_two.yml
name: first play
hosts: web.example.com
tasks:
- name: first task
yum:
name: httpd
status: present
- name: second task
service:
name: httpd
enabled: true
-
name: second play
hosts: database.example.com
tasks:
- name: first task
service:
name: mariadb
enabled: true