Getting started with DevOps Ansible

###  DevOps  Ansible Up and Running   ####

Ansible is  a configuration  management and provisioning tooL similar to Chef , Puppet and Salt stack.
Ansible Tasks are idempotent. Without a lot of extra coding, bash scripts are usually not safety run again and again. Ansible uses "Facts", which is system and environment information it gathers ("context") before running Tasks.
Ansible uses these facts to check state and see if it needs to change anything in order to get the desired outcome. This makes it safe to run Ansible Tasks against a server over and over again.


An introduction to Ansible Configuration Management :

A Brief History about configuration management system :

* CFEngine - Released 1993. Written in C

* Puppet - Released 2005 - Written in Ruby. Domain Specific Language (DSL. SSL Nightmare.)

* Chef - Released 2009 - Written in Ruby, also a DSL, more like pure Ruby

* Juju - Released 2010, Python, Very ubuntu.

* Salt - Released 2011, Python, Never got it working right

* Ansible - Released 2012, Python.  Awesome


Note :  You can install Ansible upon any linux flavour but here i am using  REDhat 7.1

Pr-requisite: 

To install ansible you need python2.6 or later
Note:   if you wish to manage windows host then also install python2-winrm

Important :    For linux and unix based machine target nodes must have 2.6 python version or later if they python 2.5 or smaller then  python-simplejson must be installed on target nodes.

If selinux is enabled then  libselinux-python  must be installed on target nodes.




1)  Installing Ansible  

i)  Method first  :-  Using  RPM  package  or with YUM command

ii)  Method Second :-  Using  python based PIP  installer


Step 1:   First install Pip installer you don't have in your redhat 6.4/7.1

[root@desktop83 ~]# yum  install python-pip

then Install ansible :

[root@desktop83 ~]# pip  install  ansible

After Installation  process this operation  you can check there will be  /etc/ansible directory

OR :

You can use Yum installer if you have repopath setup already.


 For Redhat 6.4 and later
==================

[root@desktop57 ~]# rpm -ivh  http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

[root@desktop57 ~]#  yum   install  ansible

 For Redhat 7.1 and Later

[root@desktop57 ~]# rpm -iUvh http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm

[root@desktop57 ~]#  cd /etc/yum.repos.d

[root@desktop57 yum.repos.d]# cat  live.repo 
[aa]
baseurl=http://mirror.centos.org/centos-7/7.2.1511/os/x86_64/
gpgcheck=0

[bb]
baseurl=http://mirror.centos.org/centos-7/7.2.1511/extras/x86_64/
gpgcheck=0




[root@desktop57 ~]#  yum   install  ansible
root@ashulinux:/etc/ansible# cd  /etc/ansible/
root@ashulinux:/etc/ansible# ls
hosts

Step 2:  Managing  Servers

Ansible was designed to managed multiple servers from a single system by using SSH

Important :

Here We have  three  machine  one is Ansible  installed  and other two are the targets where we want to perform operation

Ansible Installed machine is :   192.168.100.104


Target1 --   192.168.100.9
target2 --   192.168.100.10 


Note:   Setup and  and share ssh-keys  from  Ansible machine to target

i)  Generating  ssh-keys

 [root@hmaster ~]# ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
fe:4c:85:36:03:b8:3a:35:35:ec:70:f0:28:bb:ee:a1 root@hmaster.example.com
The key's randomart image is:
+--[ RSA 2048]----+
|      .          |
|       *         |
|    . + B        |
|     o * o .     |
|    . + S = .    |
|     + o . +     |
|    =   . .      |
|   o o   +       |
|  E.o     o      |
+-----------------+

ii)  share keys to both the targets machine 

[root@hmaster ~]# ssh-copy-id   192.168.100.9
[root@hmaster ~]# ssh-copy-id   192.168.100.10



Now go to Ansible machine and configure the hosts file

iii)   make a backup of host file

root@ashulinux:~# cp  /etc/ansible/hosts    /etc/ansible/hosts.backup

iv)  Now edit this file and specify the targets IPS

Important:   File  /etc/ansible/hosts    also known as inventory file


root@ashulinux:~# vim  /etc/ansible/hosts

This will look like this

root@ashulinux:~# cat  /etc/ansible/hosts
[testing]
192.168.100.9
192.168.100.10


v)  Running  Some basic commands


sending  icmp packets

a)   Sending  Icmp echo-request



root@ashulinux:~# ansible    testing   -m  ping
192.168.100.9 | success >> {
    "changed": false,
    "ping": "pong"
}

192.168.100.10 | success >> {
    "changed": false,
    "ping": "pong"
}

Here:

ansible  :-  is the command
testing  :-  name defined in inventory file for calling  all the list server
-m       :-  use for specify the module name
ping     :   This is the name of  module which simply send icmp packets to all the define servers


b)   In case you have many entries in inventory file then want to send icmp packets

root@ashulinux:~# vim  /etc/ansible/hosts

root@ashulinux:~# cat    /etc/ansible/hosts
[testing]
192.168.100.9
192.168.100.10

[apache]
192.168.100.11


root@ashulinux:~# ansible   all -m ping  
192.168.100.10 | success >> {
    "changed": false,
    "ping": "pong"
}

192.168.100.9 | success >> {
    "changed": false,
    "ping": "pong"
}

192.168.100.11 | success >> {
    "changed": false,
    "ping": "pong"
}

Note:  

all  :  for  all inventory file  entries


##########
Modules:

Modules are predefined functions in ansible which are used to perform some specific task :
I am listing some names with examples of modules.

Module LIst:

a)  ping
b)  shell
c)  command
=========
example:  testing  date command

root@ashulinux:~# ansible  testing  -m   shell  -a  date
192.168.100.109 | success | rc=0 >>
Thu Feb 18 06:54:36 EST 2016

-------------------------------------------------------


root@ashulinux:~# ansible  all  -m   shell  -a  date
192.168.100.109 | success | rc=0 >>
Thu Feb 18 06:54:45 EST 2016

192.168.100.108 | success | rc=0 >>
Thu Feb 18 06:54:53 EST 2016

----------------------------------------

Service  Restart for apache web services 

root@ashulinux:~# ansible  all  -m   shell  -a  "service  httpd  restart"
192.168.100.109 | success | rc=0 >>

192.168.100.108 | success | rc=0 >>

Using command modules:

root@ashulinux:/etc/ansible# ansible all -m command  -a  "date"
192.168.100.109 | success | rc=0 >>
Fri Feb 19 01:06:51 EST 2016

192.168.100.108 | success | rc=0 >>
Fri Feb 19 01:07:04 EST 2016

Note:  with shell module you need to pass  -a  option  for passing  arguments

Note:  you can find list of module index by clicking  below given link

http://docs.ansible.com/ansible/modules_by_category.html

Step 3:-

Managing  Basic PlayBook

Playbook can run multiple Tasks and provide some more advanced functionality that we would miss out on using ad-hoc commands. Let's move the above Task into a playbook.

Playbooks and Roles in Ansible all use YaML.

Creating YAML file for installing  Nginx webserver


Note: Simple ansible Playbook

hosts – carrying hosts information
roles/ - defining what each type of server has to perform
       webservers/
              tasks/ - tasks performed on webservers
                     main.yml
              handlers/ - running tasks under particular events
                     main.yml
              templates/ - configuration files which can reference variables
                     index.html.j2
              files/ - files to be copied to webservers
                     cloud.png


Important:

Here  hosts == pointing to  all  hosts inside   /etc/ansible/hosts

Note:  One more sample file:

- name: install and configure webservers
hosts: apache
remote_user: ec2-user
sudo: yes
roles:
   - apache
-------------------------------------------
-------------------------------------------
If we want to log into our host machines using a different username and with sudo privileges, we need to use the “remote_user” and “sudo: yes” parameter in our site.yml file. There can be additional parameters too, but they’re not needed right now. Here, we have also defined roles granted to hosts in the [webservers] group.
------------------------------------------
------------------------------------------


Method for error free playbook methods according to YAML syntax:

i) creating  apache web server yml file

[root@be04c6686478 ansible]# cat  apache_final.yml 
---
- hosts: webserver
  vars:
    http_port: 80
    max_client: 300
  remote_user: root
  tasks:
  - name: installing  httpd and check
    yum:
      name: httpd
      state: latest
  - name: start the apache service
    service:
      name: httpd
      state: started
      enabled: yes


ii)  Run yml file

[root@be04c6686478 ansible]# ansible-playbook  apache_final.yml

PLAY [webserver] **************************************************************

GATHERING FACTS ***************************************************************
ok: [192.168.0.183]

TASK: [installing  httpd and check] *******************************************
ok: [192.168.0.183]

TASK: [start the apache service] **********************************************
changed: [192.168.0.183]

PLAY RECAP ********************************************************************
192.168.0.183              : ok=3    changed=1    unreachable=0    failed=0




iii)   managing  containers using ansible  

1.  launching  containers 

---

 - hosts: test

   remote_user: root

   tasks:

    - name: creating   container 

      docker_container:

       name: ashutoshhtest1

       image: centos6shh

       detach: true 

  

       2.   Launching  multiple containers      

---

 - hosts: test

   remote_user: root

   tasks:

    - name: creating   container 

      docker_container:

       name: "container{{ item }}"

       image: centos6shh

       detach: true 

       

    

      with_sequence: count=6

   3.   removing containers 

---

 - hosts: test

   remote_user: root

   tasks:

    - name: removing container

      docker_container:

       name: ashutoshh

       state: absent       

   4.   starting containers 

---

 - hosts: test

   remote_user: root

   tasks:

    - name: starting   container 

      docker_container:

       name: ashutoshhne

       image: centos6shh

       state: started

5.   stoping containers 

---

 - hosts: test

   remote_user: root

   tasks:

    - name: stop a running container

      docker_container:

       name: ashutoshhne

       state: stopped

6.  container with volume 

---

 - hosts: test

   remote_user: root

   tasks:

    - name: creating   container with volume

      docker_container:

       name: ashutoshhtest2

       image: centos6shh

       command: ping localhost

       detach: true 

       volumes:

        - /data