1.0 - Setting up Ansible

During this lab you will configure Ansible. You will be able to use Ansible on the controller-node and run your first commands on the ansible-nodes.

You have the IPs of the controller host and manageable nodes (given by your instructor). The controller host is where you execute Ansible from and the nodes represent the machines you like to manage. We will do some configurations on the controller as well.

To make it easier for inexperienced users, we installed an editor and terminal on the controller, accessible from your browser. You can then connect to the nodes from there.

Unless otherwise specified, your working directory for all labs should be /home/ansible/techlab/.

Some good advice:

Always read all the tasks first. Some tasks might not be clear until you get the whole scope of the lab.
Open a terminal that you use only for ansible-doc (see later) and one terminal that you use for ad hoc commands (see later) to check the result of your plays.
Copypaste all the filenames etc. from the labs to your playbooks. You’ll make fewer mistakes.

Connect to your control host

Webbrowser

Connect to your control host by pasting the DNS name into your webbrowser

https://<dnsname>

username: ansible
password: << web password >>

After a successful login you should see an editor similar to visual studio code in your browser. In the navigation bar you can open “Terminal” or press ctrl-shift-^ to open a terminal. Do this now and then continue with the installation of Ansible.

SSH

You can access the nodes using SSH as well. Use your favourite SSH client to connect to the ip of your control host as user ansible.

Task 1

Install all packages needed to use Ansible on the controller.

Use sudo to elevate your privilege to those of root. Be sure to only use root priviledges for installing the packages, you should do the rest of the lab as user ansible.

Test if you can connect to the nodes from your controller using SSH. Use their public IPs.
Make sure python is installed on your nodes before continuing with the lab.

Task 2

Create a SSH-keypair for the ansible user on the controller.
Don’t set a password for the private key! Just hit ENTER at the prompt.
Enable SSH-key login for the ansible user on all nodes and the controller by distributing the SSH-public key.
Test the login on the nodes.

Task 3

Create an inventory file named hosts in your working directory with your public IPs:

[controller]
controller ansible_host=<your-controller-ip>

[web]
node1 ansible_host=<your-node1-ip>

[db]
node2 ansible_host=<your-node2-ip>

Instead of copying the ssh-id to the controller itself you could set “ansible_connection=local” in the inventory file for host “controller”. Then ansible would not use ssh to connect to the controller, but use the “local” transport mechanism. If you have a valid /etc/hosts file containing information about lab hosts, you can omit the “ansible_host=<>” parts in the inventory file.

Check if ansible is ready using the ping module to ping all hosts in your inventory

Task 4

Configure the ansible user to have root privilege on all hosts in your inventory file. Also enable login without a password for this user.
Test the functionality by running sudo -v as user ansible on all nodes.

If you are using the lab servers provided by your teacher, the sudoers configuration is already done. Anyways have a look at it to see how stuff works.

TASK 5

extend the inventory with a group nodes that has the groups ẁeb and db as members
ping all servers in the group nodes

Solutions

Installing Ansible with root privileges:

$ sudo yum -y install centos-release-ansible-29-1-1.el8.noarch
$ sudo yum -y install ansible

Opening a SSH connection:

 $ ssh -l ansible <node-ip>

Enter “yes” when prompted if you want to continue connecting
Insert your SSH-password you received from your instructor when prompted and hit return

On the nodes:

$ which python # (or which python3)
/usr/bin/python

$ ssh-keygen #(no passphrase, just hit enter until the end)
$ ssh-copy-id <node-ip>

Follow the prompt and enter the ansible user password you received from your instructor:

Don’t forget your controller and the second node.

usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/ansible/.ssh/id_rsa.pub"
The authenticity of host '5.102.146.128 (5.102.146.128)' can't be established.
ECDSA key fingerprint is SHA256:5PmNPnSzE2IS309kJ8fAKrAjk0/NZT91qC4zQo0Vwiw.
ECDSA key fingerprint is MD5:43:5f:9c:e1:ad:b5:76:a1:fa:5d:09:9c:be:5d:c2:7e.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
ansible@5.102.146.128's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh '5.102.146.128'"
and check to make sure that only the key(s) you wanted were added.

Test it by running the SSH command executed on that node:

$ ssh <node-ip> hostname
[yourusernamehere]-node1

$ ansible all -i hosts -m ping
5.102.146.128 | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "ping": "pong"
}
...
...

Ansible options explained:
-i is synonymous with --inventory and expects an inventory file.
-m is synonymous with --module-name and expects an ansible module.

In the file /etc/sudoers (On CentOS/RHEL), there’s already a config entry for the wheel group that is similar to the one we need for our ansible user.

$ ssh -l ansible <node-ip>
$ sudo -i
# grep wheel /etc/sudoers
## Allows people in group wheel to run all commands
%wheel  ALL=(ALL)       ALL
# %wheel        ALL=(ALL)       NOPASSWD: ALL # <-- this line!

Add a similar line for user ansible to the sudoers file:

# echo 'ansible ALL=(ALL)   NOPASSWD: ALL' >> /etc/sudoers

Check if ansible user has root privileges:

sudo -v

Note that you cannot do this using Ansible yet. The reason being you need root privileges and we are just setting up those right now.

$ cat hosts
[controller]
control0 ansible_host=192.168.122.30
 
[web]
node1 ansible_host=192.168.122.31
 
[db]
node2 ansible_host=192.168.122.32
 
[nodes:children]
web
db

Updated on 22 Apr 2020