Revision as of 02:02, 7 November 2018

Example: Secure Nginx Server

This page walks through a procedure resulting in the following files:

    playbooks/ansible.cfg
    playbooks/hosts
    playbooks/Vagrantfile
    playbooks/web-notls.yml
    playbooks/web-tls.yml
    playbooks/files/nginx.key
    playbooks/files/nginx.crt
    playbooks/files/nginx.conf
    playbooks/templates/index.html.j2
    playbooks/templates/nginx.conf.j2

Before you begin: Vagrant configuration

This assumes we will be setting up a Ubuntu machine using Vagrant. (See Vagrant page for steps.)

Before starting, we want to remap some ports.

We want to arrange the Vagrant machine so that we map the local port 8080 to the vagrant machine's port 80, and map the local port 8443 to the vagrant machine's port 443.

The Vagrantfile is a Ruby file that specifies how to start up and set up the Vagrant boxes. The Vagrantfile should be modified as follows:

VAGRANTFILE_API_VERSION = "2"

Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
  config.vm.box = "ubuntu/xenial64"
  config.vm.network "forwarded_port", guest: 80, host: 8080
  config.vm.network "forwarded_port", guest: 443, host: 8443
end

Now instruct vagrant to reload from the Vagrantfile:

$ vagrant reload

==> default: Forwarding ports...
    default: 80 => 8080 (adapter 1)
    default: 443 => 8443 (adapter 1)
    default: 22 => 2222 (adapter 1)

Creating a simple playbook

The following simple playbook will set up an nginx web server on our fresh Ubuntu machine.

The Pieces

Here are the pieces in our playbook:

The playbook itself (YAML file)
nginx configuration file
nginx HTML templates
Create Ansible group webservers

The Playbook: YAML file

Here is a simple playbook for our secure nginx server:

web-notls.yml:

- name: Configure webserver with nginx
  hosts: webservers
  become: True
  tasks:
    - name: install nginx
      apt: name=nginx update_cache=yes

    - name: copy nginx config file
      copy: src=files/nginx.conf dest=/etc/nginx/sites-available/default

    - name: enable configuration
      file: >
        dest=/etc/nginx/sites-enabled/default
        src=/etc/nginx/sites-available/default
        state=link

    - name: copy index.html
      template: src=templates/index.html.j2 dest=/usr/share/nginx/html/index.html
        mode=0644

    - name: restart nginx
      service: name=nginx state=restarted

Required files: /etc/nginx/sites-available/default, /usr/share/nginx/html/index.html

YAML truth-y values: true, True, TRUE, yes, Yes, YES, on, On, ON, y, Y

YAML false-y values: false, False, FALSE, no, No, NO, off, Off, OFF, n, N

nginx config file

Here is the corresponding nginx configuration file, which we put in files/nginx.conf:

files/nginx.conf:

server {
        listen 80 default_server;
        listen [::]:80 default_server ipv6only=on;

        root /usr/share/nginx/html;
        index index.html index.htm;

        server_name localhost;

        location / {
                try_files $uri $uri/ =404;
        }
}

nginx index html page

Likewise, we want to create an index page for nginx to serve up, and we want to put template files into the playbook directory, in the templates subdirectory.

(NOTE: .j2 extension means it is a Jinja 2 template)

playbooks/templates/index.html.j2

<html>
  <head>
    <title>Welcome to ansible</title>
  </head>
  <body>
  <h1>nginx, configured by Ansible</h1>
  <p>If you can see this, Ansible successfully installed nginx.</p>

  <p>Running on {{ inventory_hostname }}</p>
  </body>
</html>

Creating webservers Ansible group

We will create a webservers Ansible group in the inventory file and refer to this group in the Ansible playbook.

In the playbooks/hosts file the "myvagrantbox" line is put under the heading [webservers]:

playbooks/hosts

[webservers]
myvagrantbox ansible_host=127.0.0.1 ansible_port=2222

Now test it out: ping the webservers group with a single command:

$ ansible webservers -m ping

Output:

testserver | success >> {
    "changed": false,
    "ping": "pong"
}

Running a simple playbook

The ansible-playbook command is used to execute playbooks:

ansible-playbook web-notls.yml

Alternatively, to run a playbook directly, use the shebang line:

#!/usr/bin/env ansible-playbook

Then execute it directly:

./web-notls.yml

Anatomy of a playbook

Let's examine the example playbook in detail.

Plays

A playbook is a list of plays.

Every play has:

a set of hosts to configure
a set of tasks to run on those hosts
the play is the thing that connects hosts to tasks

Optional play settings:

name - a comment that describes what the play is about
become - if true, Ansible will run each task by becoming the root user (useful for Ubuntu, where ssh as root is disabled by default)
vars - list of variables and values

In our example, the play is this entire section:

- name: Configure webserver with nginx
  hosts: webservers
  become: True
  tasks:
    - name: install nginx
      apt: name=nginx update_cache=yes

    - name: copy nginx config file
      copy: src=files/nginx.conf dest=/etc/nginx/sites-available/default

    - name: enable configuration
      file: >
        dest=/etc/nginx/sites-enabled/default
        src=/etc/nginx/sites-available/default
        state=link

    - name: copy index.html
      template: src=templates/index.html.j2
               dest=/usr/share/nginx/html/index.html mode=0644


    - name: restart nginx
      service: name=nginx state=restarted

Tasks

The tasks are the actions that are performed when the play is run.

The first task is to install nginx:

- name: install nginx
  apt: name=nginx update_cache=yes

This can also be written without the optional name parameter,

- apt: name=nginx update_cache=yes

Can also fold over multiple lines using >:

- name: install nginx
  apt: >
      name=nginx
      update_cache=yes

Actions in tasks are composed of modules.

Modules

There are lots of useful modules that come with Ansible that can be used from playbooks.

apt - installs/removes packages using aptitude package manager
copy - copies files from local machine to host
file - sets attributes of files/symlinks/directories
service - starts/stops/restarts a service
template - generates a file from a template and copies it to the hosts

Flags

Ansible/Playbooks: Difference between revisions

From charlesreid1