Ansible Setup on Linux — Step-by-Step Guide

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Prerequisites

• Two Ubuntu Linux machines (e.g., node-1, node-2 on Azure/AWS)
• SSH access with a user that has sudo privileges

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Step 1: Connect to Your Linux Machine

ssh username@<your-server-ip>

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Step 2: Update the System

sudo apt update && sudo apt upgrade -y

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Step 3: Install Python

sudo apt install python3 python3-pip -y
python3 --version   # verify

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Step 4: Install Ansible

sudo apt install software-properties-common -y
sudo add-apt-repository --yes --update ppa:ansible/ansible
sudo apt install ansible -y
ansible --version   # verify

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Step 5: Create the ansible User

sudo adduser ansible

Enter a password when prompted and fill in (or skip) the optional details.

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Step 6: Grant ansible User Sudo Permissions (Passwordless)

As per industry standard, the Ansible user should have passwordless sudo/privilege escalation on all nodes.

echo "ansible ALL=(ALL) NOPASSWD:ALL" | sudo tee /etc/sudoers.d/ansible
sudo chmod 440 /etc/sudoers.d/ansible

sudo sed -i 's/PasswordAuthentication no/PasswordAuthentication yes/' /etc/ssh/sshd_config.d/60-cloudimg-settings.conf && sudo systemctl restart ssh

Verify it works:

su - ansible
sudo whoami   # should print: root

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Step 7: Set Up SSH Key-Based Auth for ansible User

On your control machine (laptop/workstation):

ssh-keygen -t ed25519 -f ~/.ssh/ansible_key
ssh-copy-id -i ~/.ssh/ansible_key ansible@<node-1-ip>
ssh-copy-id -i ~/.ssh/ansible_key ansible@<node-2-ip>

Test passwordless login:

ssh -i ~/.ssh/ansible_key ansible@<node-1-ip>
ssh -i ~/.ssh/ansible_key ansible@<node-2-ip>

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Step 8: Verify Ansible Connectivity

Create a quick inventory file:

# inventory.ini
[nodes]
<node-1-ip>
<node-2-ip>
[nodes]
node1 ansible_host=192.168.1.10 ansible_user=ansible

Run a ping test:

ansible -i inventory.ini all -m ping --user ansible --private-key ~/.ssh/ansible_key
ansible all -m ping
ansible nodes -m ping
# check inventory is correct
ansible nodes --list-hosts

# ping with verbose output
ansible nodes -m ping -v

# ping with explicit user and key
ansible nodes -m ping -u ansible --private-key ~/.ssh/id_ed25519

You should see pong back from each node — you’re all set!

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How Ansible Uses SSH (Background)

• Ansible reads IP addresses and credential info from the inventory file
• Internally runs an SSH command to connect to each node
• Generates a temporary Python script for your configuration and copies it to the node
• Python on the node executes the script and returns output via SSH
• Ansible then cleans up the temporary files automatically

redhat

# 1. Create the user 'ansible'
sudo useradd -m -s /bin/bash ansible

# 2. Set password for 'ansible'
echo "ansible:YourPasswordHere" | sudo chpasswd

# 3. Add 'ansible' to sudo group
sudo usermod -aG sudo ansible

# 4. Enable password authentication in SSH
sudo sed -i 's/^#PasswordAuthentication no/PasswordAuthentication yes/' /etc/ssh/sshd_config
sudo sed -i 's/^PasswordAuthentication no/PasswordAuthentication yes/' /etc/ssh/sshd_config

# 5. Restart SSH service to apply changes
sudo systemctl restart sshd