Hands-on Ansible Tutorial with Ansible installation, usage, and configuration with Ansible Modules:
We discussed about AWS Elastic Beanstalk in our previous tutorial.
LIST of Tutorials in this Ansible Series:
Ansible is an open source tool that helps in task automation, application deployment, cloud provisioning and configuration management.
Also Read =>DevOps Training Tutorial list
So we are talking about IT orchestration where tasks are run in sequence in several different machines or servers.
Ansible does this by connecting to multiple machines through SSH and runs the tasks which have been configured into playbooks and uses a simple language called YAML (Yet Another Markup Language).
What You Will Learn:
Overview of Ansible
Most importantly Ansible does not use an agent to automate tasks on different machines.
Ansible ensures maintaining exact versions and up to date information to the software packages.
For Example, if you want to install JDK 8 or Tomcat or any other software package in 10 or 20 different machines it is not actually feasible to go to all the machines and install them rather use Ansible to automate the installation or even software deployments using Playbooks and Inventory written in a very simple language.
So Ansible is:
- Free and Open Source
- Maintained by Redhat
- Essentially a server configuration
- Configuration Management
In this 3 part Ansible Tutorial series, we will discuss hands-on approach on the following topics:
- Installation and configuration process
- Ansible Modules
- Ad-hoc commands,
- Task automation using playbooks
- Ansible roles
- Ansible vault
- Ansible and AWS
Ansible Installation Process
Ansible can be installed and run from any machine.
Typically you will need a Control machine for installation which should be Linux. Windows machine does not support being a control machine. The control machine will manage the other remote machines. As mentioned earlier Ansible uses SSH to manage remote machines.
Throughout this tutorial, I will be using AWS EC2 instances to showcase the examples. I have used 2 instances (one control machine and other as a target for automating tasks) and Redhat Linux 7.5.
Whether on-premise or cloud instances you will need to open ports appropriately based on the tasks being automated. I have the following ports open as a part of the security group for the EC2 instances to demonstrate the examples mentioned in the tutorial.
In the above screen, I have mentioned opening port 8080 as I will be showing about automating software deployment automation using Tomcat which will be useful from a DevOps point of view, especially during the continuous delivery process.
Installation of Ansible using YUM
As mentioned before I will be using one control machine and a target machine. To start with installation, perform the steps as shown below in both the machines.
a) Create a common id on both the machines, for Example, ansible with SUDO privileges. This id will be used for communicating across all the machines involved for automation of tasks.
# useradd ansible # passwd ansible
b) Edit the /etc/ssh/sshd_config file on the control machine and uncomment out the lines for PasswordAuthentication and PermitRootLogin
Perform the above steps on both the machines. Once completed, restart the sshd service on both the machines.
# systemctl restart sshd
c) For complete automation of tasks, we will need passwordless SSH authentication else the whole process will not be used if you have to key in the password every time.
So post the changes done above if we run the command ssh <target machine> and ssh <control machine> we will need to key in the password every time which is not the right procedure to execute Ansible tasks.
d) To enable passwordless authentication to perform the steps shown below. Firstly add the user ansible to the /etc/sudoers file on both the machines which will enable the user ansible to run any command which requires root privileges.
Save and exit the file after adding the user.
e) Going forward we will use the user ansible to perform all the steps. So switch to the user ansible.
Control Machine su – ansible AND Target Machine su – ansible
Control Machine ssh-keygen
Target Machine ssh-keygen
Copy the ssh key to the target machine and vice versa.
Control Machine ssh-copy-id <IP-Address-Host-Machine>
Target Machine ssh-copy-id <IP-Address-Control-Machine>
We are now able to log in without entering the password. After the check out of the ssh connectivity on both the machines and be logged in as ansible user.
Control Machine: ssh ansible@<IP-Address-Host-Machine
Target Machine: ssh ansible@<IP-Address-Control-Machine>
f) Install wget if not installed on both the machines.
$ sudo yum install wget -y
g) We can now install ansible on the Control machine only by enabling the EPEL repo from fedora which provides add-on software packages. Perform the following steps to install ANSIBLE.
$ wget http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm $ sudo rpm -ivh epel-release-latest-7.noarch.rpm $ sudo yum install ansible -y $ ansible --version
The ansible version used is 2.5.3
h) Edit the ansible.cfg file and enable the inventory file parameter on the Control machine.
$ sudo vi /etc/ansible/ansible.cfg
i) Ansible uses the concept of Inventory to manage and track the target machines. By default, this file is located in /etc/ansible/hosts and can be changed as well. A host file consists of groups for better classification and multiple machines under the group. All the required machines can be added to those groups.
Every group is denoted by a square bracket and a group name within. A server can actually exist in multiple groups.
Edit the inventory file /etc/ansible/hosts and add all the servers which need to be managed.
j) To test the connectivity of the servers under the webserver’s group run the ansible ping command as shown. Here ping is a module which performs a particular function to test whether the hosts can be connected as defined in the inventory file or not. We will see more about various modules and its examples in the next section.
$ ansible webservers –m ping
To list the hosts in the inventory file, you can run the below command
$ ansible webservers --list-hosts
Ansible consist of 3 main components
- Control Machine
The control machine manages the execution of the Playbook. It can be installed on your laptop or on any machine on the internet.
The Inventory file provides a complete list of all the target machines on which various modules are run by doing an ssh connection and install the necessary software’s.
The playbook consists of steps that the control mechanism will perform on the servers defined in the inventory file.
Very important to understand here is that Ansible interacts with all the servers defined in the inventory through the SSH protocol which is a secure method of remote login. Every operation is done and file transfer is encrypted.
So as you would have seen in the previous section Ansible does not use any kind of database for installation and is very easy to install, we will now proceed with the actual usage of Ansible starting with Modules which is the main building block.
Modules are the main building blocks of Ansible and are basically reusable scripts that are used by Ansible playbooks. Ansible comes with a number of reusable modules. These include functionality for controlling services, software package installation, working with files and directories etc.
The syntax is as follows while running the ad-hoc commands which help in running single or simple tasks just once and which need not be run later. For E.g. just installing Tomcat on all servers.
ansible hostORgroup -m module_name -a "arguments" -u username --become
Let’s have a look at some of the most popular Ansible modules and their usage through the ad-hoc commands and later on in the playbook.
#1) Setup Module
To get information about the network or hardware or OS version or memory related information the setup module will help to gather the same about the target machines. On the control, the machine runs the below command.
$ ansible webservers –m setup
#2) Command Module
The command module simply executes a specific command on the target machine and gives the output.
Some of the Examples are given below
$ ansible webservers –m command - an ‘uptime’ $ ansible webservers –m command –a ‘hostname’
#3) Shell Module
To execute any command in the shell of your choice you can use the Shell module. The shell module commands are run in /bin/sh shell and you can make use of the operators like ‘>’ or ‘|’ (pipe symbol or even environment variables.
So primarily the difference between the Shell and Command module is that if you actually do not need to use the operators like the ones mentioned then you could use the command module.
$ ansible webservers -m shell -a 'ls -l > temp.txt'
On the machines under webservers group check for the file created and run the command to view the text file.
$ ansible webservers –m command -a ‘cat temp.txt’
#4) User Module
Using this module one can create or delete users.
To add user
$ ansible webservers -m user -a 'name=user1 password=user1' --become
To delete user
$ ansible webservers -m user -a 'name=user1 state=absent' --become
- become – Privilege to the superuser to run the command
- state=absent to delete the user
#5) File Module
This module is used to create files, directories, set, or change file permissions and ownership etc
Example 1: Create a file
$ ansible webservers -m file -a 'dest=/home/ansible/niranjan.txt state=touch mode=600 owner=ansible group=ansible'
Example 2: Create a directory
To create a directory using the file module, you need to set two parameters.
- Path(alias – name, dest) – This is the absolute path of the directory to be created.
- State – You should enter the value as ‘directory.’ By default, the value is ‘file’.
$ ansible webservers -m file -a "dest=/home/ansible/vndir state=directory mode=755"
Example 3: Delete a file
$ ansible webservers -m file -a "dest=/home/ansible/niranjan.txt state=absent"
Example 4: Delete a directory
You can delete a directory by setting the state parameter value to absent. The directory and all its contents will be deleted.
$ ansible webservers -m file -a "dest=/home/ansible/vndir state=absent"
#6) Copy Module
It is used for copying files to multiple target machines.
$ ansible webservers -m copy -a "src=sample.txt dest=/home/ansible/sample.txt"
#7) Managing Software Packages
If you need to install software packages through ‘yum’ or ‘apt’ you can use the below commands.
Example 1: Install GIT
$ ansible webservers –m yum -a “name=git state=present” --become
On the right-hand window, you can see if git is not installed it will give command not found and once installed it will show up the output.
In this command, state=present will check if the package is installed or not and if not installed it will install the latest version.
Example 2: Check if the package is installed & update it to the latest version.
$ ansible webservers -m yum -a “name=git state=latest”
In the above command, state=latest will update the package to the latest version only.
Example 3: Install Apache Webserver
$ ansible webservers -m yum -a "name=httpd state=present" –become
Example 4: Check if Maven is installed or not.
$ ansible webservers -m yum -a "name=maven state=absent" –become
#8) Managing Services Module
To manage services with ansible, we use a module ‘service’.
Starting a service
$ ansible webservers -m service -a “name=httpd state=started” --become
Stopping a service
$ ansible webservers -m service -a “name=httpd state=stopped” --become
Restarting a service
$ ansible webservers -m service -a “name=httpd state=restarted --become
Click here to get the Complete Module list.
In this tutorial, I introduced you to the basic concepts and components of Ansible and we also have seen more about installation, configuration, and usage of Ansible with the help of Ansible modules which is the main component in Ansible execution.
In our upcoming tutorial, we will focus on the very important aspect of writing playbooks for task automation and Ansible vaults to keep sensitive data in encrypted files.