SSH Keys and DNS Resolution
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In this lesson, you will learn about setting up DNS entries and SSH key authentication for Ansible-managed nodes. By the end of this lesson, you will be able to create DNS entries in the hosts file for your managed nodes and Ansible controller, generate an SSH key pair, deploy it to your managed nodes, and verify SSH connectivity from the Ansible controller to the managed nodes.
Setting Up DNS Entries
DNS (Domain Name System) resolution is crucial for network communication. In many cases, especially in test environments, you might need to manually set up DNS entries. We'll start by adding entries to the /etc/hosts file on the Ansible controller for managed-node-1, managed-node-2, and the ansible-controller itself.
Open the /etc/hosts file on the Ansible controller with a text editor. You will need root or sudo privileges to edit this file:
nano /etc/hostsNow add the following to at the bottom of your hosts file:
# Ansible nodes
192.168.1.200 managed-node-1
192.168.1.201 managed-node-2Save the file and exit the editor. This allows us to use the name managed-node-1 instead of remembering and typing its IP address, 192.168.1.200. It will come in handy later!
Creating an SSH Key Pair
SSH keys provide a secure way of logging into a server without using a password. Let's generate an SSH key pair on the Ansible controller. Run the following command to generate an SSH key pair:bash
ssh-keygen -t rsa -b 4096When prompted, you can press Enter to use the default file location. Optionally, set a passphrase for additional security.
Deploying the SSH Key
Next, we'll deploy the public key to managed-node-1 and managed-node-2. This will allow the Ansible controller to SSH into these nodes without a password. We will use the ssh-copy-id command to copy the public key to each managed node. Replace username with the actual username on the managed nodes:
Replace paulh with the actual username you set up when installing the OS on the VMs
ssh-copy-id paulh@ansible-controller
ssh-copy-id paulh@managed-node-1
ssh-copy-id paulh@managed-node-2You will be prompted to verify the key fingerprint of each server, and enter the password for each managed node. Type yes when you receive these prompts (you should receive two of them):
Are you sure you want to continue connecting (yes/no/[fingerprint])? yesAnd type in the password you used when you installed the OS on the respective VMs when prompted. If all went well, you should see a message like following for all three servers:
paulh@managed-node-1's password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh 'paulh@managed-node-1'"
and check to make sure that only the key(s) you wanted were added.You may have noticed that we copied our SSH key to the same server we were already SSH'd into. The reason for this is to set up the Ansible Controller using Ansible itself. Since Ansible will try to SSH into itself, it's necessary to prepare the SSH keys in advance, similar to how we would for other hosts.
Verifying SSH Connectivity
Finally, let's verify that you can SSH from the Ansible controller into each managed node without being prompted for a password.
SSH into managed-node-1 (replace paulh with your username):
ssh paulh@managed-node-1If you're not prompted for a password and successfully log in, the key deployment was successful. Exit back to the Ansible controller:
exitRepeat the SSH testing process for managed-node-2, ansible-controller and verify that you can SSH without entering a password.
Conclusion
You've successfully set up DNS entries for your Ansible environment, created an SSH key pair, deployed it to your managed nodes, and verified SSH connectivity. This setup is essential for efficient and secure Ansible automation.
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