How to Install and Configure Ansible on CentOS 9 Stream

[group_name]
alias ansible_ssh_host=your_server_ip

This  group_name is an organizational tag that allows you to refer to any server listed below that tag with one word. An alias is just a name for that server.

Imagine you have three servers that you want to control using Ansible. Ansible communicates with clients via SSH, so each server you want to manage must be accessible from the Ansible server by entering:

 ssh root@your_server_ip 

You should not be prompted for a password. While Ansible is certainly capable of handling password-based SSH authentication, SSH keys keep things simple.

We will assume that our server’s IP address is  192.168.0.1, 192.168.0.2and 192.168.0.3. Let’s set this up so we can call them individually  host1,  host2, and  host3, or in groups as  servers. To configure this, you would add this block to your hosts file:

[servers]
host1 ansible_ssh_host=192.168.0.1
host2 ansible_ssh_host=192.168.0.2
host3 ansible_ssh_host=192.168.0.3

Servers can belong to multiple groups, and groups can configure parameters for all of their members. Try this now.

By default, Ansible will attempt to connect to remote servers using your current username. If that user does not exist on the remote system, connection attempts will result in this error

host1 | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh.",
    "unreachable": true
}

Please specifically tell Ansible that it will connect to the servers in the “server” group with user greencloud  . Create a folder in the Ansible configuration structure named  group_vars.

 mkdir /etc/ansible/group_vars 

In this folder we can create YAML formatted files for each group we want to configure:

 vi /etc/ansible/group_vars/servers 

Add this code to the file:

---
ansible_ssh_user: greencloud

YAML files start with “—”, so make sure you don’t forget that part.

Save and close this file when you’re done. Now Ansible will always use user sammy  for  servers the group, regardless of the current user.

If you want to specify configuration details for every server, regardless of group affiliation, you can put those details in a file at  /etc/ansible/group_vars/all. Individual servers can be configured by creating files in a directory at  /etc/ansible/host_vars.

Use simple Ansible commands

Now that we have the server set up and have enough configuration details to allow us to successfully connect to our server, we can try our first command.
Ping all the servers you have configured by entering:

 ansible -m ping all 

Ansible will return results like this:

host1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

host3 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

host2 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

This is a basic test to ensure that Ansible has connectivity to all of its servers.

Part  -m ping of the command is to instruct Ansible to use the “ping” module. These are basically commands that you can run on your remote server. The ping module works in many ways like the regular ping utility in Linux, but instead it checks the Ansible connection.

This part  all means “all servers”. You can easily specify a group:

 ansible -m ping servers 

You can also specify an individual server:

 ansible -m ping servers 

You can specify multiple servers by separating them with a colon:

 ansible -m ping host1:host2 

The shell module allows us to send terminal commands to a remote server and retrieve the results. For example, to find out the memory usage on server1, we can use:

 ansible -m shell -a 'free -m' host1 

As you can see, you pass arguments into the script using the -a switch. Here’s what the output might look like:

host1 | SUCCESS | rc=0 >>
             total       used       free     shared    buffers     cached
Mem:          3954        227       3726          0         14         93
-/+ buffers/cache:        119       3834
Swap:            0          0          0

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