Ansible Play-book and Role Tutorial

Ansible

Ansible is configuration management, IT automation and provisioning tool. With the help of Ansible automation tool, we can configure and manage ‘n’ number of servers at a time. When executing a task Ansible use ssh to login to the remote machine. It is an agentless automation tool.

Environment setup.

To set up our environment I am using Oracle Virtual-box. In my virtual-box Manager, I have installed 2 Centos-7 Virtual machines. One is Control machine, where we will install Ansible, I named it “ctrlmachine” other one is host machine or the machine which we will execute the tasks.

ctrlmachine : 192.168.1.28

Remote node1: 192.168.1.29

To learn about Virtual-box installation please refer below links.

VirtualBox VM installation

Ansible installation.

Login to  ctrlmachine and install ansible

To install Ansible packages we need to enable EPEL repository in Centos 7. To enable the EPEL repository  click here.

Once you enabled EPEL repository, you can install Ansible with the help of yum package manager.

Execute the below command to install Ansible.

[root@localhost ~]# yum install ansible

To check the installed Ansible version

[root@ctrlmachine ~]# ansible --version
ansible 2.7.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.5 (default, Apr 11 2018, 07:36:10) [GCC 4.8.5 20150623 (Red Hat 4.8.5-28)]

Ansible configuration

Ansible will use a password or public-private key mechanism to perform any task on remote nodes. Here we use key authentication, for this create an ssh key on ctrlmachine using below command

#ssh-keygen -t rsa -b 4096

The key file will be generated in /root/.ssh/id_rsa fiel.

Now copy the public key to our remote nodes using the ssh-copy-id command.

[root@ctrlmachine ~]# ssh-copy-id root@192.168.1.29
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.1.29's password:
Number of key(s) added: 1

 

Now try logging into the machine, with “ssh ‘root@192.168.1.29′”
and check to make sure that only the key(s) you wanted were added.

Make sure that, we can log in to the node1 machine without entering a password by executing below command.

[root@ctrlmachine ~]# ssh root@192.168.1.29
Last failed login: Tue Apr 2 06:33:03 EDT 2019 from 192.168.1.28 on ssh:notty
Last login: Tue Apr 2 06:32:29 2019 from 192.168.1.26
[root@localhost ~]#

The same method we use to copy the public key of ctrlmachine to copy all remote nodes. Here I have done it for the first node.

Ansible hosts files

This file is used to add the remote node details. We can add remote node IP address or hostname, so Ansible ctrlmachine can understand which hosts need to connect. I am adding our first node IP address to this file.

[root@ctrlmachine ~]# vim /etc/ansible/hosts

In the last line of the file, I have added the IP address as follows, we can add more hosts and the group name is called “webserver”. You can give any name here.

[webserver]
192.168.1.29

Ansible Ad-hoc commands

We have installed Ansible and configured it now the time to run Ansible command. Here we will execute some basic command and understand it.

To reach all remote nodes from host machine execute the ping command

# ansible -m ping all

Here -m is module all to execute in all nodes. The command was successful and we can see the output on the terminal.

Now execute ping command with our host group name and see the output.

Try some shell command

# ansible -m command -a "df -h" webserver

We can execute other commands in the same way or with the help of shell module. In the next chapter, we will learn ansible playbooks.

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