Ansible Quick Start

Ansible Quick Start Tasks and Solutions

1. Installation and Configuration2. Running Ansible Commands
3. Playbook Structure with YAML
4. Gathering Facts
5. Variable Substitution6. Debug Statement7. Notifications and Handlers

Installation and Configuration

Task 1: Install Ansible

Pre-requisites:

$ sudo yum instal epel-release
$ sudo yum update

Solution:

Step 1: Install Ansible with required dependencies

 $ sudo yum install git python python-devel python-pip openssl ansible

Step 2: Check Whether Ansible installed or not

 $ ansible --version

============================================

Task 2: Configure ansible

Solution:

Step 1: Modify the ansible configuration file as below

 $ sudo vi /etc/ansible/ansible.cfg

→ Uncomment the below code in ansible.cfg file

inventory = /etc/ansible/hostssudo_user = root

Step 2: Take the backup of hosts file under ansible directiory

$ cd /etc/ansible         #Change to ansible directory
$ sudo mv hosts hosts.original       #Backup hosts file
$ sudo vi hosts

→ Add the hostnames under hosts file

[group-name1]
hostname1
hostname2 ..
[group-name2]
hostname1
hostname2 …

→ Save and Close

→ Here we are going to use ansible as non-previleged user that must have sudo rights.

→ To get the permissions we need to setup some settings

Step 3: Create a user for ansible

$ sudo adduser ansible
$ sudo passwd ansible

New password:

Re-Enter password:

 $ sudo visudo       #Add the ansible user

→ Find the below code

## Allows root to run any commands anywhere
root ALL=(ALL) ALL→ Add the below lines at the above code
ansible ALL=(ALL) NOPASSWD: ALL

→ Save and Close

NOTE: Repeat the Step 3 on all the hosts that are added in /etc/ansible/hosts file.

=====================================

Task 3: Setup ssh-key exchange

Solution:

Step 1: Generate ssh-key under ansible directory

 $ su ansible    # Login to ansible user
$ ssh-keygen    # Generate ssh-key

Step 2: Copy the generated key on to the nodes

$ ssh-copy-id username@hostname or node IP
$ ssh-copy-id ansible@hostname or node IP     #Give the hostname or node IP as in hosts files

Step 3: Login remotely onto the node

→ When logged into the node it wouldn’t ask the password after copying the ssh-key.

$ ssh ansible@hostname or node IP
$ exit

NOTE: Repeat Step 2 and Step 3 for the nodes that are added in hosts file.

Step 4: copy the generated key onto the ansible server to login witout password

 $ ssh-copy-id server-ip or server-hostname

→ Check the conectivity

$ ssh server-hostname # It must be logged in without password
$ exit

Running Ansible Commands

Task-1: Run Ansible commands

Solution:

Step 1: Run a single command on all the hosts that are present in the hosts file

 $ ansible all -m ping     #Here all indicates all the hosts that are present in hosts file

Step 2: List everything under /home/ansible directory on all nodes

 $ ansible all -a “ls -al /home/ansible”

Step 3: View the content under previleged /var/log/messages file

 $ ansible all -a “cat /var/log/messages”    #We need to be root to view the previleged files

→ Modify the above command a little bit

 $ ansible all -s -a “cat /var/log/messages”      # Now we can view the content of the file without password.

Copy the files to the nodes using ansible

Step 4: Create a directory and create a text file under the directory

 $ cd
$ cd ansible # change to the directory ansible
$ sudo vi test.txt

→ Add some content into the text file

→ Save and Close

Step 5: Copy the text file to the nodes

 $ ansible hostname(or groupname) -m copy -a “src=test.txt dest=/tmp/test.txt”

Install and remove the packages on the nodes using ansible

Step 6: Install the package

 $ ansible hostname(or groupname) -s -m yum -a “name=name of the package to be installed state=latest”

Step 7: Remove the packages

 $ ansible hostname(or groupname) -s -m yum -a “name=name of the package to be Removed state=absent”

Adding and Removing user on the nodes using ansible

Step 8: Adding user to the nodes

 $ ansible hostname(or groupname) -s -m user -a “name=test”

Step 9: Removing user on thr nodes

 $ ansible hostname(or groupname) -s -m user -a “name=test state=absent”

Playbook Structure with YAML

Task: Write a playbook to install httpd package

Solution:

Step1: Create a .yaml file

 $ cd ansible
$ sudo mkdir playbook
$ cd playbook
$ sudo vi structure.yaml

---      #This is a structural YAML example to install HTTPD
- hosts: hostname(or group-name)    #give the hostname or group-name which has mentioned in the hosts file
  remote_user: ansible         #The user you setup
  become: yes      #Going to become troot user through become_method
  become_method: sudo          #It defined in the configuration file by default
  connection: ssh
  gather_facts: yes         #Its gets the information about the operating system
  vars:
    username: myuser
  tasks:
  - name: Install HTTPD server on <specified node>
    yum:          #Module how you are going to install the package
      name: httpd
      state: latest
      notify:
      - startservice
    handlers:
    - name: startservice
      service:
      name: httpd
      state: restarted

→ Save and Close

Step 2: calling a playbook

 $ ansible-playbook structure.yml

Step 3: check the status of httpd on the specified node

 $ sudo systemctl status httpd

Step 4: Delete the installed package

$ ansible hostname(or group-name) -s -m yum -a “name=httpd state=absent”

Gathering Facts

Task: Gathering Facts

$ ansible all --list-hosts        #To see the list of hosts under hosts file
$ cd /ansible/playbooks
$ ansible hostname(or group-name) -m setup      # Setting up the gathering facts
$ ansible hostname(or group-name) -m setup | grep ipv4
$ ansible hostname(or group-name) -m setup -a ‘filter=*ipv4*’      #gathering facts of ipv4
$ ansible hostname(or group-name) -m setup -a ‘filter=*default*’     # gathering facts for default
$ ansible hostname(or group-name) -m setup --tree facts    # Gathering the facts to fats directory
$ cd facts
$ vi hostname #you can find all the facts in this file
$ ansible hostname(or group-name) -m setup -a ‘filter=fact-name’
$ ansible all -m setup --tree facts #Gathering all the hosts facts into a single directory

Variable Substitution

Task 1: How to assign variables in playbook

Solution:

Step 1: create a playbook that has variables to install package

 $ cd ansible/playbook
$ vi vartest.yaml

--- # Testing how variables work in the vars section of a playbook
- hosts: ‘{{ myhosts}}’
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: ‘{{ gather }}’
  vars:
    myhosts: hostname(or group-name)
    gather: yes
    pkg: telnet
  tasks: 
  - name: Install the indicated software
    yum:
      name: ‘{{ pkg }}’
      state: latest

Step 2: Run playbook

 $ ansible-playbook vartest.yaml

Step 3: Remove the package

$ ansible hostname(or group-name) -s -m yum -a “name=telnet state=absent”

Step 4: Install the package through command line

 $ ansible hostname(or group-name) -s -m yum -a “name=telnet state=latest”         #Installing package through command line

Step 5: Write another playbook for variable substitution

 $ sudo cp vartest.yaml varsubst.yaml

$ sudo vi varsubst.yaml

→ Modify the code as below

--- # Testing how variables work in the vars section of a playbook 
- hosts: ‘{{ myhosts}}’
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: ‘{{ gather }}’
  tasks: 
  - name: Install the indicated software
     yum:
       name: ‘{{ pkg }}’
       state: latest

→ Save and Close.

Step 6: Install package through variable substitution

 $ ansible-playbook varsubst.yaml --extra-vars ‘myhosts=hostname(group-name) gather=yes pkg=telnet’

Step 7: Delete the installed package on node

$ ansible hostname(or group-name) -s -m yum -a “name=telnet state=absent”

Debug Statement

Task: How to use debug method in playbook

Solution:

Step 1: Write a playbook to install a package with debug method

 $ sudo vi debug.yaml

→ Write the following code

--- # Playbook demo of debug and register statement 
- hosts: hostname(or group-name)
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: no
  tasks: 
  - name: Installing telnet package 
    yum:
      name: telnet
      state: latest

→ Save and Close.

Step 2: Run Playbook

 $ ansible-playbook debug.yaml

Step 3: Go to the respective node to check whether the package is installed or not

$ telnet
telnet&gt; quit

Step 4: Delete the package

 $ ansible hostname(or group-name) -s -m yum -a “name=telnet state=absent”

Step 5: Modify the playbook as below

 $ sudo vi debug.yaml

--- # Playbook demo of debug and register statement 
- hosts: hostname(or group-name)
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: no
  tasks: 
  - name: Installing telnet package 
    yum:
      name: telnet
      state: latest
      register: result
   - debug: var=result

→ Save and Close

Step 6: Run Playbook

$ ansible-playbook debug.yaml

Step 7: Delete the installed package on node

$ ansible hostname(or group-name) -s -m yum -a “name=telnet state=absent”

Notifications and Handlers

Task: How to write Notifications and Handling events in a playbook

Solution:

Step 1: create a playbook

 $ sudo vi notify.yaml

--- # Notificaton and Handling events
- hosts: hostname(or group-name)
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: yes
  tasks: 
  - name: install http server 
     yum:
       name: httpd
       state: latest
     - name: enable and start the http service
        service: 
          name: httpd
          enabled: yes
          state: restarted

→ Save and Close

Step 2: Run Playbook

 $ ansible-playbook notify.yaml

Step 3: Goto respective node to check the package is installed or not

$ sudo systemctl status httpd

Step 4: Delete the installed package on node

$ ansible hostname(or group-name) -s -m yum -a “name=telnet state=absent”

Step 5: Add the notifier in the playbook

 $ sudo vi notify.yaml

--- # Notificaton and Handling events
- hosts: hostname(or group-name)
  remote_user: ansible
  become: yes
  become_method: sudo
  connection: ssh
  gather_facts: yes
  tasks: 
  - name: install nginx web server 
    yum:
      name: nginx
      state: latest
      notify:
      - enable and start the nginx service
  handlers: 
  - name: enable and start the nginx service
    service: 
      name: nginx
      enabled: yes
      state: restarted

→ Save and Close

Step 6: Run the modified playbook.

 $ ansible-playbook notify.yaml

→ Observe the difference while executing the command

Step 7: Remove the installed package

 $ ansible hostname(or group-name) -s -m yum -a “name=httpd state=absent”

Step 8: Goto respective node to check the package is installed or not

$ sudo systemmctl status httpd

→ It shows not running

Karunakar

Wednesday, October 24, 2018

Ansible Quick Start

Ansible Quick Start

Installation and Configuration

Running Ansible Commands

Playbook Structure with YAML

Gathering Facts

Variable Substitution

Debug Statement

Notifications and Handlers

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