Ansible Tutorial for Beginner
Ansible Tutorial : Ansible is simple open source IT engine which automates application deployment, intra service orchestration, cloud provisioning and many other IT tools.
This tutorial is prepared for the beginners to help them understand the basics of Ansible. It can also help as a guide to engineers.
Before you start doing practice with various types of examples given in this tutorial, it is being assumed that you have hands-on experience with running commands into a Linux shell. This will help you the Ansible tasks in a better way.
Ansible – Introduction
Ansible is simple open source IT engine which automates application deployment, intra service orchestration, cloud provisioning and many other IT tools.
Ansible is easy to deploy because it does not use any agents or custom security infrastructure.
Ansible uses playbook to describe automation jobs, and playbook uses very simple language i.e. YAML (It’s a human-readable data serialization language & is commonly used for configuration files, but could be used in many applications where data is being stored)which is very easy for humans to understand, read and write. Hence the advantage is that even the IT infrastructure support guys can read and understand the playbook and debug if needed (YAML – It is in human readable form).
Ansible is designed for multi-tier deployment. Ansible does not manage one system at time, it models IT infrastructure by describing all of your systems are interrelated. Ansible is completely agentless which means Ansible works by connecting your nodes through ssh(by default). But if you want other method for connection like Kerberos, Ansible gives that option to you.
After connecting to your nodes, Ansible pushes small programs called as “Ansible Modules”. Ansible runs that modules on your nodes and removes them when finished. Ansible manages your inventory in simple text files (These are the hosts file). Ansible uses the hosts file where one can group the hosts and can control the actions on a specific group in the playbooks.
Sample Hosts File
This is the content of hosts file −
#File name: hosts#Description: Inventory file for your application. Defines machine type abcnode to deploy specific artifacts# Defines machine type def node to uploadmetadata. [abc-node]#server1 ansible_host = <target machine for DU deployment> ansible_user = <Ansibleuser> ansible_connection = sshserver1 ansible_host = <your host name> ansible_user = <your unix user>ansible_connection = ssh [def-node]#server2 ansible_host = <target machine for artifact upload>ansible_user = <Ansible user> ansible_connection = sshserver2 ansible_host = <host> ansible_user = <user> ansible_connection = ssh
What is Configuration Management
Configuration management in terms of Ansible means that it maintains configuration of the product performance by keeping a record and updating detailed information which describes an enterprise’s hardware and software.
Such information typically includes the exact versions and updates that have been applied to installed software packages and the locations and network addresses of hardware devices. For e.g. If you want to install the new version of WebLogic/WebSphere server on all of the machines present in your enterprise, it is not feasible for you to manually go and update each and every machine.
You can install WebLogic/WebSphere in one go on all of your machines with Ansible playbooks and inventory written in the most simple way. All you have to do is list out the IP addresses of your nodes in the inventory and write a playbook to install WebLogic/WebSphere. Run the playbook from your control machine & it will be installed on all your nodes.
How Ansible Works?
The picture given below shows the working of Ansible.
Ansible works by connecting to your nodes and pushing out small programs, called “Ansible modules” to them. Ansible then executes these modules (over SSH by default), and removes them when finished. Your library of modules can reside on any machine, and there are no servers, daemons, or databases required.
The management node in the above picture is the controlling node (managing node) which controls the entire execution of the playbook. It’s the node from which you are running the installation. The inventory file provides the list of hosts where the Ansible modules needs to be run and the management node does a SSH connection and executes the small modules on the hosts machine and installs the product/software.
Beauty of Ansible is that it removes the modules once those are installed so effectively it connects to host machine , executes the instructions and if it’s successfully installed removes the code which was copied on the host machine which was executed.
Ansible – Environment Setup
In this chapter, we will learn about the environment setup of Ansible.
Mainly, there are two types of machines when we talk about deployment −
- Control machine − Machine from where we can manage other machines.
- Remote machine − Machines which are handled/controlled by control machine.
There can be multiple remote machines which are handled by one control machine. So, for managing remote machines we have to install Ansible on control machine.
Control Machine Requirements
Ansible can be run from any machine with Python 2 (versions 2.6 or 2.7) or Python 3 (versions 3.5 and higher) installed.
Note − Windows does not support control machine.
By default, Ansible uses ssh to manage remote machine.
Ansible does not add any database. It does not require any daemons to start or keep it running. While managing remote machines, Ansible does not leave any software installed or running on them. Hence, there is no question of how to upgrade it when moving to a new version.
Ansible can be installed on control machine which have above mentioned requirements in different ways. You can install the latest release through Apt, yum, pkg, pip, OpenCSW, pacman, etc.
Installation through Apt on Ubuntu Machine
For installing Ansible you have to configure PPA on your machine. For this, you have to run the following line of code −
$ sudo apt-get update $ sudo apt-get install software-properties-common $ sudo apt-add-repository ppa:ansible/ansible $ sudo apt-get update $ sudo apt-get install ansible
After running the above line of code, you are ready to manage remote machines through Ansible. Just run Ansible–version to check the version and just to check whether Ansible was installed properly or not.
Ansible – Ad hoc Commands
Ad hoc commands are commands which can be run individually to perform quick functions. These commands need not be performed later.
For example, you have to reboot all your company servers. For this, you will run the Adhoc commands from ‘/usr/bin/ansible’.
These ad-hoc commands are not used for configuration management and deployment, because these commands are of one time usage.
ansible-playbook is used for configuration management and deployment.
Parallelism and Shell Commands
Reboot your company server in 12 parallel forks at time. For this, we need to set up SSHagent for connection.
$ ssh-agent bash $ ssh-add ~/.ssh/id_rsa
To run reboot for all your company servers in a group, ‘abc’, in 12 parallel forks −
$ Ansible abc -a "/sbin/reboot" -f 12
By default, Ansible will run the above Ad-hoc commands form current user account. If you want to change this behavior, you will have to pass the username in Ad-hoc commands as follows −
$ Ansible abc -a "/sbin/reboot" -f 12 -u username
You can use the Ad-hoc commands for doing SCP (Secure Copy Protocol) lots of files in parallel on multiple machines.
Transferring file to many servers/machines
$ Ansible abc -m copy -a "src = /etc/yum.conf dest = /tmp/yum.conf"
Creating new directory
$ Ansible abc -m file -a "dest = /path/user1/new mode = 777 owner = user1 group = user1 state = directory"
Deleting whole directory and files
$ Ansible abc -m file -a "dest = /path/user1/new state = absent"
The Ad-hoc commands are available for yum and apt. Following are some Ad-hoc commands using yum.
The following command checks if yum package is installed or not, but does not update it.
$ Ansible abc -m yum -a "name = demo-tomcat-1 state = present"
The following command check the package is not installed.
$ Ansible abc -m yum -a "name = demo-tomcat-1 state = absent"
The following command checks the latest version of package is installed.
$ Ansible abc -m yum -a "name = demo-tomcat-1 state = latest"
Facts can be used for implementing conditional statements in playbook. You can find adhoc information of all your facts through the following Ad-hoc command −
$ Ansible all -m setup