Getting Started with Ansible on Ubuntu

Part 1 - This is a getting started series on Ansible.

The first post will be on how to setup ansible and how to reach your nodes in order to deploy software to your nodes.

Install Ansible:

Ansible relies on python, so we will first install the dependencies:

$ apt update && apt install python python-setuptools -y
$ easy_install pip
$ pip install ansible

Populate the invetory configuration:

Your invetory file will hold your host and variable information. Lets say we have 3 nodes that we want to deploy software to; node-1, node-2 and node-3. We will group them under nodes. This will be saved under the a new file inventory.init:

inventory.ini

[nodes]
node-1
node-2
node-3

Next we will populate information about our node names, this will be done under our ~/.ssh/config configuration:

~/.ssh/config

Host node-1
  Hostname 10.0.0.2
  User root
  IdentityFile ~/.ssh/id_rsa
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Host node-2
  Hostname 10.0.0.3
  User root
  IdentityFile ~/.ssh/id_rsa
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Host node-3
  Hostname 10.0.0.4
  User root
  IdentityFile ~/.ssh/id_rsa
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null

Now we need to generate a ssh key for our node where we will run our ansible commands from:

$ ssh-keygen -b 2048 -f ~/.ssh/id_rsa -t rsa -q -N ""

Now we will copy the contents of ~/.ssh/id_rsa.pub into our destination nodes ~/.ssh/authorized_keys or if you have password authentication enabled, we can do $ ssh-copy-id root@10.0.0.x etc. Now we should be able to ssh to our nodes to node-1, node-2 and node-3.

Deploy Python:

As Ansible requires Python, we need to bootstrap our nodes with Python. Since we are able to ssh to our nodes, we will use ansible to deploy Python to our nodes:

$ ansible -m raw -s -a "apt update && apt install python -y" -i inventory.ini nodes

This should succeed, then we can test our connection by running the ping module:

$ ansible -i inventory.ini nodes -m ping
node-2 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
node-3 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
node-1 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

Run a command on your nodes:

Let's run a cat command on all the nodes:

$ ansible -i inventory.ini nodes -a "/bin/cat /etc/hostname"
node-3 | SUCCESS | rc=0 >>
node-3

node-1 | SUCCESS | rc=0 >>
node-1

node-2 | SUCCESS | rc=0 >>
node-2

Ansible Playbooks:

Let's run shell commands, the traditional hello world, using the ansible-playbook command. First we need a task definition, which I will name shell_command-1.yml:

---
# Echo Static String
- hosts: nodes
  tasks:
  - name: echo static value
    shell: /bin/echo "hello world"
    register: echo_static
  - debug: msg="{{echo_static.stdout}}"

Now we have defined that our commands will be executed against the host group defined in our inventory.ini. Let's run our ansible playbook command:

$ ansible-playbook -i inventory.ini shell_command.yml

PLAY [nodes] *************************************************************************************

TASK [Gathering Facts] **********************************************************************************
ok: [node-1]
ok: [node-2]
ok: [node-3]

TASK [echo static value] ********************************************************************************
changed: [node-1]
changed: [node-2]
changed: [node-3]

TASK [debug] ********************************************************************************************
ok: [node-1] => {
    "msg": "hello world"
}
ok: [node-2] => {
    "msg": "hello world"
}
ok: [node-3] => {
    "msg": "hello world"
}

PLAY RECAP **********************************************************************************************
node-1              : ok=3    changed=1    unreachable=0    failed=0
node-2              : ok=3    changed=1    unreachable=0    failed=0
node-3              : ok=3    changed=1    unreachable=0    failed=0

Let's define a variable location_city = Cape Town in our inventory.ini configuration, then we will call the variable key in our task definition:

[nodes]
node-1
node-2
node-3

[nodes:vars]
location_city="Cape Town"

Now our task definition with our variable:

---
# Echo Variable
- hosts: nodes
  tasks:
  - name: echo variable value
    shell: /bin/echo "{{ location_city }}"
    register: echo
  - debug: msg="{{echo.stdout}}"

Running our ansible-playbook:

$ ansible-playbook -i inventory.ini shell_command.yml

PLAY [nodes] **************************************************************************************************************************************************************************************

TASK [Gathering Facts] ***********************************************************************************************************************************************************************************
ok: [node-1]
ok: [node-2]
ok: [node-3]

TASK [echo variable value] *******************************************************************************************************************************************************************************
changed: [node-1]
changed: [node-2]
changed: [node-3]

TASK [debug] *********************************************************************************************************************************************************************************************
ok: [node-1] => {
    "msg": "Cape Town"
}
ok: [node-2] => {
    "msg": "Cape Town"
}
ok: [node-3] => {
    "msg": "Cape Town"
}

PLAY RECAP ***********************************************************************************************************************************************************************************************
node-1              : ok=3    changed=1    unreachable=0    failed=0
node-2              : ok=3    changed=1    unreachable=0    failed=0
node-3              : ok=3    changed=1    unreachable=0    failed=0

This is it for this post, all posts for this tutorial will be posted under #ansible-tutorials

Thank You

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