Configuration Management
This is process of configuring remote servers from one point of control.
Advantages
1) Provisioning of servers
The applications that should be installed on server can be done very quickly from a single centralized location.
2) Idempotent
Configuration management tools are used to bring the server to a particular state, called as desired state. If a server already in the desired state, configuration management tools will not reconfigure that server.
Note: Cofiguration management tools cannot be used for installing OS from the scratch.
They can be used only for managing the applications on top of the OS.
COnfigutaion management tools – Ansible, chef, puppet, salt etc
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Ansible — It is a open source configuration management tool, created using Python.
Main machine in which anisble is installed, is called as controller.
Remote severs that Ansible configures, are called as managed nodes.
Ansible uses agent less policy for configures remote servers ie Ansible is installed only on 1 machine, and we do not require any client side software to be installed on the remote serers.
Ansible performs configuration management through password less ssh.
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Create 4 Servers ( Ubuntu 18 )
1 is controller
3 are managed nodes
Name the instances as
Controller
Server1
Server2
Server3
Ubuntu machines default come with Python3
Ansible supports Python2
We need to install Python2
Connect server1
Check the version
$ python3 –version
To Install Python2
$ sudo apt-get update
$ sudo apt-get dist-upgrade ( It will point to older apt repository where python2 is available)
$ sudo apt-get install -y python2.7 python-pip
$ sudo apt-get install python3-pip
Now check the version of python
$ python –version
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Establish password less ssh connection
$ sudo passwd ubuntu
( lets give the password as ubuntu only )
$ sudo vim /etc/ssh/sshd_config
change
PasswordAuthentication yes
Save and QUIT
$ sudo service ssh restart
$ exit
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Repeat the same steps in server2 and server3
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Now, Connect to controller
Even in controller also python2 version should be available
(So, run the same commands)
$ sudo apt-get update
$ sudo apt-get dist-upgrade
$ sudo apt-get install -y python2.7 python-pip
Now check the version of python
$ python –version
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Now , We need to generate ssh connections
$ ssh-keygen
Now copy the key to managed nodes
$ ssh-copy-id ubuntu@172.31.0.98 ( private Ip of server1 )
$ ssh-copy-id ubuntu@172.31.1.183 ( private Ip of server2 )
$ ssh-copy-id ubuntu@172.31.14.179 ( private Ip of server3 )
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Installing ansible now
Connect to controller.
$ sudo apt-get install software-properties-common
( software-properties-common , is a base package which is required to install ansible )
$ sudo apt-add-repository ppa:ansible/ansible
$ sudo apt-get update
$ sudo apt-get install -y ansible
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To check ther version of ansible
$ ansible –version
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Write the ip address of nodes in the inventory file
$ cd /etc/ansible
$ ls
$ sudo vim hosts
insert the private ip addresss of 3 servers
save and quit
$ ls -la ( to see the list in the current machine )
$ ansible all -a ‘ls -la’ ( you will get the list of the files in all managed nodes )