Introduction to Ansible

Alejandro Guirao Rodríguez

github.com/lekum

Architecture overview

Source: sysadmincasts

Environment installation

Vagrantfile

VAGRANTFILE_API_VERSION = "2"
Vagrant.configure(VAGRANTFILE_API_VERSION) do |config|
    config.ssh.insert_key = false
    config.vm.provider :virtualbox do |vb|
        vb.customize ["modifyvm", :id, "--memory", "256"]
    end

    # Web server 1
    config.vm.define "web01" do |web|
        web.vm.hostname = "web01"
        web.vm.box = "ubuntu/trusty64"
        web.vm.network :private_network, ip: "10.0.15.21"
    end

    # Web server 2
    config.vm.define "web02" do |web|
        web.vm.hostname = "web02"
        web.vm.box = "ubuntu/trusty64"
        web.vm.network :private_network, ip: "10.0.15.22"
    end

    # Database server.
    config.vm.define "db01" do |db|
        db.vm.hostname = "db1"
        db.vm.box = "ubuntu/trusty64"
        db.vm.network :private_network, ip: "10.0.15.23"

        config.vm.provider "virtualbox" do |vb|
            vb.customize ['createhd', '--filename', 'disk.vdi', '--size', 5 * 1024]
            vb.customize ['storageattach', :id, '--storagectl', 'SATAController', '--port', 1, '--device', 0, '--type', 'hdd', '--medium', 'disk.vdi']
        end

    end
end

Host file (inventory)

[web]
10.0.15.21
10.0.15.22

[db]
10.0.15.23

# Variables that will be applied to all servers
[all:vars]
ansible_ssh_user=vagrant

More info and options: docs.ansible.com/intro_inventory.html

Ad Hoc Commands

  • Throw-away, one-time actions
  • Execution of an Ansible module in each host of a group
  • Run by the "ansible" command using this syntax:

ansible group -m module -a options -i host_file

Let's assume that the host file is located at /etc/ansible/hosts

Hello World!: Ping

(ansible)alex ~ $ ansible all -m ping
10.0.15.22 | success >> {
    "changed": false, 
    "ping": "pong"
}

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

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

ansible all -m ping

Let's check the hostnames

(ansible)alex ~ $ ansible all -a "cat /etc/hostname"
10.0.15.22 | success | rc=0 >>
web02

10.0.15.21 | success | rc=0 >>
web01

10.0.15.23 | success | rc=0 >>
db1

ansible all -a "cat /etc/hostname"

If no module is specified, then the command module is used

Let's install ntp, first in the db

(ansible)alex ~ $ ansible db -s -m apt -a "name=ntp update_cache=yes"
10.0.15.23 | success >> {
    "changed": true, 
    "stderr": "", 
    "stdout": "Reading package lists...\nBuilding dependency tree...\nReading state information...\nThe following extra packages will be installed:\n  libopts25\nSuggested packages:\n  ntp-doc\nThe following NEW packages will be installed:\n  libopts25 ntp\n0 upgraded, 2 newly installed, 0 to remove and 62 not upgraded.\nNeed to get 473 kB of archives.\nAfter this operation, 1676 kB of additional disk space will be used.\nGet:1 http://archive.ubuntu.com/ubuntu/ trusty/main libopts25 amd64 1:5.18-2ubuntu2 [55.3 kB]\nGet:2 http://archive.ubuntu.com/ubuntu/ trusty-updates/main ntp amd64 1:4.2.6.p5+dfsg-3ubuntu2.14.04.2 [418 kB]\nFetched 473 kB in 5s (82.2 kB/s)\nSelecting previously unselected package libopts25:amd64.\n(Reading database ... 60960 files and directories currently installed.)\nPreparing to unpack .../libopts25_1%3a5.18-2ubuntu2_amd64.deb ...\nUnpacking libopts25:amd64 (1:5.18-2ubuntu2) ...\nSelecting previously unselected package ntp.\nPreparing to unpack .../ntp_1%3a4.2.6.p5+dfsg-3ubuntu2.14.04.2_amd64.deb ...\nUnpacking ntp (1:4.2.6.p5+dfsg-3ubuntu2.14.04.2) ...\nProcessing triggers for man-db (2.6.7.1-1ubuntu1) ...\nProcessing triggers for ureadahead (0.100.0-16) ...\nSetting up libopts25:amd64 (1:5.18-2ubuntu2) ...\nSetting up ntp (1:4.2.6.p5+dfsg-3ubuntu2.14.04.2) ...\n * Starting NTP server ntpd\n   ...done.\nProcessing triggers for libc-bin (2.19-0ubuntu6.5) ...\nProcessing triggers for ureadahead (0.100.0-16) ...\n"
}

ansible db -s -m apt -a "name=ntp update_cache=yes"

The -s option runs the module with sudo

Let's install ntp in every machine

(ansible)alex ~ $ ansible all -s -m apt -a "name=ntp update_cache=yes"
10.0.15.23 | success >> {
    "changed": false
}

10.0.15.22 | success >> {
    "changed": true, 
    "stderr": "", 
    "stdout": "Reading package lists...\nBuilding dependency tree...\nReading state information...\nThe following extra packages will be installed:\n  libopts25\nSuggested packages:\n  ntp-doc\nThe following NEW packages will be installed:\n  libopts25 ntp\n0 upgraded, 2 newly installed, 0 to remove and 62 not upgraded.\nNeed to get 473 kB of archives.\nAfter this operation, 1676 kB of additional disk space will be used.\nGet:1 http://archive.ubuntu.com/ubuntu/ trusty/main libopts25 amd64 1:5.18-2ubuntu2 [55.3 kB]\nGet:2 http://archive.ubuntu.com/ubuntu/ trusty-updates/main ntp amd64 1:4.2.6.p5+dfsg-3ubuntu2.14.04.2 [418 kB]\nFetched 473 kB in 7s (67.3 kB/s)\nSelecting previously unselected package libopts25:amd64.\n(Reading database ... 60960 files and directories currently installed.)\nPreparing to unpack .../libopts25_1%3a5.18-2ubuntu2_amd64.deb ...\nUnpacking libopts25:amd64 (1:5.18-2ubuntu2) ...\nSelecting previously unselected package ntp.\nPreparing to unpack .../ntp_1%3a4.2.6.p5+dfsg-3ubuntu2.14.04.2_amd64.deb ...\nUnpacking ntp (1:4.2.6.p5+dfsg-3ubuntu2.14.04.2) ...\nProcessing triggers for man-db (2.6.7.1-1ubuntu1) ...\nProcessing triggers for ureadahead (0.100.0-16) ...\nSetting up libopts25:amd64 (1:5.18-2ubuntu2) ...\nSetting up ntp (1:4.2.6.p5+dfsg-3ubuntu2.14.04.2) ...\n * Starting NTP server ntpd\n   ...done.\nProcessing triggers for libc-bin (2.19-0ubuntu6.5) ...\nProcessing triggers for ureadahead (0.100.0-16) ...\n"
}

10.0.15.21 | success >> {
    "changed": true, 
    "stderr": "", 
    "stdout": "Reading package lists...\nBuilding dependency tree...\nReading state information...\nThe following extra packages will be installed:\n  libopts25\nSuggested packages:\n  ntp-doc\nThe following NEW packages will be installed:\n  libopts25 ntp\n0 upgraded, 2 newly installed, 0 to remove and 62 not upgraded.\nNeed to get 473 kB of archives.\nAfter this operation, 1676 kB of additional disk space will be used.\nGet:1 http://archive.ubuntu.com/ubuntu/ trusty/main libopts25 amd64 1:5.18-2ubuntu2 [55.3 kB]\nGet:2 http://archive.ubuntu.com/ubuntu/ trusty-updates/main ntp amd64 1:4.2.6.p5+dfsg-3ubuntu2.14.04.2 [418 kB]\nFetched 473 kB in 6s (76.9 kB/s)\nSelecting previously unselected package libopts25:amd64.\n(Reading database ... 60960 files and directories currently installed.)\nPreparing to unpack .../libopts25_1%3a5.18-2ubuntu2_amd64.deb ...\nUnpacking libopts25:amd64 (1:5.18-2ubuntu2) ...\nSelecting previously unselected package ntp.\nPreparing to unpack .../ntp_1%3a4.2.6.p5+dfsg-3ubuntu2.14.04.2_amd64.deb ...\nUnpacking ntp (1:4.2.6.p5+dfsg-3ubuntu2.14.04.2) ...\nProcessing triggers for man-db (2.6.7.1-1ubuntu1) ...\nProcessing triggers for ureadahead (0.100.0-16) ...\nSetting up libopts25:amd64 (1:5.18-2ubuntu2) ...\nSetting up ntp (1:4.2.6.p5+dfsg-3ubuntu2.14.04.2) ...\n * Starting NTP server ntpd\n   ...done.\nProcessing triggers for libc-bin (2.19-0ubuntu6.5) ...\nProcessing triggers for ureadahead (0.100.0-16) ...\n"
}


ansible all -s -m apt -a "name=ntp update_cache=yes"

Idempotency

Notice that the db has a key of "changed: false" in the output

Ansible modules will detect if it is necessary to perform actions to reach the desired state. If no action is needed, then nothing is done

This is called idempotency and it is key to Configuration Management, ensuring that applying the commands over and over again won't have unexpected results

Let's restart the ntp service

(ansible)alex ~ $ ansible all -s -m service -a "name=ntp state=restarted"
10.0.15.23 | success >> {
    "changed": true, 
    "name": "ntp", 
    "state": "started"
}

10.0.15.21 | success >> {
    "changed": true, 
    "name": "ntp", 
    "state": "started"
}

10.0.15.22 | success >> {
    "changed": true, 
    "name": "ntp", 
    "state": "started"
}

ansible all -s -m service -a "name=ntp state=restarted"

Enough! No more one-liners!

Ad-hoc commands may be useful for quick-and-dirty operations. But configuration management needs a more disciplined way of working

The playbooks are YAML files that specify a list of plays.

Each play is a series of tasks applied to a group of hosts

Playbooks are played with the ansible-playbook command

A playbook to deploy nginx

---
- hosts: web
  sudo: yes
  vars:
      - external_port: 80
      - internal_port: 8000

  tasks:

      - name: Add the apt repository for nginx
        apt_repository: repo="ppa:nginx/stable" update_cache=yes

      - name: Install nginx
        apt: name=nginx state=present

      - name: Ensure that nginx is started
        service: name=nginx state=started

      - name: Remove default site
        file: path=/etc/nginx/sites-enabled/default state=absent
        notify:
            - Restart nginx

      - name: Configure a site
        template: src=templates/site.j2 dest=/etc/nginx/sites-available/site

      - name: Enable a site
        file: src=/etc/nginx/sites-available/site dest=/etc/nginx/sites-enabled/site state=link
        notify:
            - Restart nginx

  handlers:
      - name: Restart nginx
        service: name=nginx state=restarted

deploy-nginx.yml

The site template

server {
    listen {{ external_port }};
    server_name {{ ansible_hostname }};

    location / {
        proxy_pass http://localhost:{{ internal_port }};
    }
}
  • Ansible uses Jinja2 for templating
     
  • The variables can be defined in several ways: in playbooks, in the inventory, in separate files, at the command line...
     
  • Some variables are automatically discovered by ansible and available for using in the playbooks: they are called facts. In this template we are using one: ansible_hostname

templates/site.j2

About facts

You can see the facts of the hosts using the module setup

ansible all -m setup

You'll get a very long list including hostnames, IPs, hardware and devices attached, installed software versions...

If you want to speed up the execution of a playbook, at the risk of losing those values, set gather_facts: no in the play

Let's run the playbook

$ ansible-playbook deploy-nginx.yml 

PLAY [web] ******************************************************************** 

GATHERING FACTS *************************************************************** 
ok: [10.0.15.21]
ok: [10.0.15.22]

TASK: [Add the apt repository for nginx] ************************************** 
changed: [10.0.15.21]
changed: [10.0.15.22]

TASK: [Install nginx] ********************************************************* 
changed: [10.0.15.22]
changed: [10.0.15.21]

TASK: [Ensure that nginx is started] ****************************************** 
ok: [10.0.15.21]
ok: [10.0.15.22]

TASK: [Remove default site] *************************************************** 
changed: [10.0.15.21]
changed: [10.0.15.22]

TASK: [Configure a site] ****************************************************** 
changed: [10.0.15.21]
changed: [10.0.15.22]

TASK: [Enable a site] ********************************************************* 
changed: [10.0.15.21]
changed: [10.0.15.22]

TASK: [Remove default site] *************************************************** 
ok: [10.0.15.21]
ok: [10.0.15.22]

NOTIFIED: [Restart nginx] ***************************************************** 
changed: [10.0.15.21]
changed: [10.0.15.22]

PLAY RECAP ******************************************************************** 
10.0.15.21                 : ok=9    changed=6    unreachable=0    failed=0   
10.0.15.22                 : ok=9    changed=6    unreachable=0    failed=0  

Encapsulation: roles

In order to create reusable components, we can define roles

Roles are a way to relate certain elements to a group of servers:

  • Variables
  • Tasks
  • Handlers
  • Files and templates
  • Dependencies to other roles

Let's create a role to install MongoDB

$ tree roles
roles
└── mongodb_server
    ├── defaults
    │   └── main.yml
    ├── handlers
    │   └── main.yml
    ├── README.md
    └── tasks
        └── main.yml

Tasks

---
- name: Add the apt-key for mongodb-org
  apt_key: keyserver=hkp://keyserver.ubuntu.com:80 id=0x7F0CEB10
  sudo: yes

- name: Add the apt repository for mongodb-org
  apt_repository: repo="deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen" update_cache=yes
  sudo: yes

- name: Make sure mongodb-org is installed
  apt: name="mongodb-org" state=latest
  sudo: yes

- name: Enable small journal files if applicable
  lineinfile: dest=/etc/mongod.conf regexp="^smallfiles =" line="smallfiles = true"
  when: small_files
  sudo: yes
  notify:
      - Restart mongodb-org

- name: Bind mongodb to every IP
  lineinfile: dest=/etc/mongod.conf regexp="^bind_ip =" state=absent
  sudo: yes
  notify:
      - Restart mongodb-org

- name: Make sure mongod is started
  service: name=mongod state=started
  sudo: yes

roles/mongodb_server/tasks/main.yml

Handlers

---
- name: Restart mongodb-org
  service: name=mongod state=restarted
  sudo: yes

Defaults

---
small_files: False

roles/mongodb_server/handlers/main.yml

roles/mongodb_server/defaults/main.yml

Using roles in a playbook

---
- hosts: db
  sudo: yes
  roles:
      - mongodb_server

  tasks:

      - name: Install the pre-requisites
        apt: name={{ item }} update_cache=yes
        with_items:
            - lvm2

      - name: Create a vg named vgdata with /dev/sdb
        lvg: vg=vgdata pvs=/dev/sdb

      - name: Create a lv named lvdata01 in vgdata
        lvol: vg=vgdata lv=lvdata01 size=80%VG

      - name: Create an ext4 filesystem in /dev/mapper/vgdata-lvdata01
        filesystem: fstype=ext4 dev=/dev/mapper/vgdata-lvdata01

      - name: Make sure mongod is stopped
        service: name=mongod state=stopped

      - name: Mount the directory
        mount: name=/var/lib/mongodb src=/dev/mapper/vgdata-lvdata01 fstype=ext4 state=mounted

      - name: Re-establish permissions for the directory
        file: path=/var/lib/mongodb owner=mongodb group=nogroup state=directory recurse=yes

      - name: Make sure mongod is started
        service: name=mongod state=started

deploy-mongo.yml

Install MongoDB!

$ ansible-playbook deploy-mongo.yml 

PLAY [db] ********************************************************************* 

GATHERING FACTS *************************************************************** 
ok: [10.0.15.23]

TASK: [mongodb_server | Add the apt-key for mongodb-org] ********************** 
ok: [10.0.15.23]

TASK: [mongodb_server | Add the apt repository for mongodb-org] *************** 
ok: [10.0.15.23]

TASK: [mongodb_server | Make sure mongodb-org is installed] ******************* 
changed: [10.0.15.23]

TASK: [mongodb_server | Enable small journal files if applicable] ************* 
skipping: [10.0.15.23]

TASK: [mongodb_server | Bind mongodb to every IP] ***************************** 
changed: [10.0.15.23]

TASK: [mongodb_server | Make sure mongod is started] ************************** 
ok: [10.0.15.23]

TASK: [Install the pre-requisites] ******************************************** 
changed: [10.0.15.23] => (item=lvm2)

TASK: [Create a vg named vgdata with /dev/sdb] ******************************** 
changed: [10.0.15.23]

TASK: [Create a lv named lvdata01 in vgdata] ********************************** 
changed: [10.0.15.23]

TASK: [Create an ext4 filesystem in /dev/mapper/vgdata-lvdata01] ************** 
changed: [10.0.15.23]

TASK: [Make sure mongod is stopped] ******************************************* 
changed: [10.0.15.23]

TASK: [Mount the directory] *************************************************** 
changed: [10.0.15.23]

TASK: [Re-establish permissions for the directory] **************************** 
changed: [10.0.15.23]

TASK: [Make sure mongod is started] ******************************************* 
changed: [10.0.15.23]

NOTIFIED: [mongodb_server | Restart mongodb-org] ****************************** 
changed: [10.0.15.23]

PLAY RECAP ******************************************************************** 
10.0.15.23                 : ok=15   changed=11   unreachable=0    failed=0   

Fun with AWS

There are many modules to manage AWS:

  • Launch and terminate EC2 instances
  • Manage EIP
  • S3 objects upload / download
  • ELB management
  • RDS
  • Route 53
  • Elasticache...

In order to use them, you will need to:

export AWS_ACCESS_KEY_ID='AK123'
export AWS_SECRET_ACCESS_KEY='abc123'

pip install boto

Let's create an EC2 instance

We will create the instance using the ec2 module

Once it is created, we register the result of the module in a variable so we can access the data of the instance.

We then use the add_host module to dinamically add the instance to the inventory...

... so that we can provision it in the next play of the playbook!

# Example to create an AWS instance and install MongoDB
#
# The region, key_name, image and security group (group) must match your configuration
#
# Before running the playbook, ensure that:
#  - The key 'demo-key' has been added to ssh-agent
#  - export ANSIBLE_HOST_KEY_CHECKING=False
#  - The environment variables AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY match your credentials
#
---
- hosts: localhost
  connection: local
  gather_facts: no
  tasks:

      - name: EC2 provisioning of MongoDB instance
        ec2:
            region: eu-west-1
            key_name: demo-key
            instance_type: t2.micro
            image: ami-234ecc54
            wait: yes
            instance_tags:
                Name: mongo-server
            exact_count: 1
            count_tag:
                Name: mongo-server
            group:
                - SSH-ACCESS
            volumes:
                - device_name: /dev/xvdc
                  # /dev/xvdc of 5 GB
                  volume_size: 5
        register: ec2

      - name: Wait for SSH to come up
        wait_for: host={{ item.public_ip }} port=22 delay=10 timeout=320 state=started
        with_items: ec2.instances

      - name: Add the host to the group to be provisioned
        add_host: name={{ item.public_ip }} groupname=to_be_provisioned
        with_items: ec2.instances

- hosts: to_be_provisioned
  user: ubuntu
  sudo: yes
  roles:

      - {
          role: mongodb_server,
          small_files: true
        }

  tasks:

      - name: Install the pre-requisites
        apt: name={{ item }} update_cache=yes
        with_items:
            - lvm2

      - name: Create a vg named vgdata with /dev/xvdc
        lvg: vg=vgdata pvs=/dev/xvdc

      - name: Create a lv named lvdata01 in vgdata
        lvol: vg=vgdata lv=lvdata01 size=80%VG

      - name: Create an ext4 filesystem in /dev/mapper/vgdata-lvdata01
        filesystem: fstype=ext4 dev=/dev/mapper/vgdata-lvdata01

      - name: Make sure mongod is stopped
        service: name=mongod state=stopped

      - name: Mount the directory
        mount: name=/var/lib/mongodb src=/dev/mapper/vgdata-lvdata01 fstype=ext4 state=mounted

      - name: Re-establish permissions for the directory
        file: path=/var/lib/mongodb owner=mongodb group=nogroup state=directory recurse=yes

      - name: Make sure mongod is started
        service: name=mongod state=started

Here we go!

deploy-aws-mongo.yml

Managing dynamic inventory

Hardcoding IPs in a file is not a valid way to manage a cloud. We need a dynamic inventory

Ansible provides dynamic inventory scripts for many clouds. The files ec2.py and ec2.ini for AWS are in github.com/ansible/ansible/tree/devel/plugins/inventory

You can inspect your cloud just typing:

./ec2.py --list

The dynamic inventory script creates groups based on tags (super cool!)

Rolling updates

Using pre_tasks and post_tasks, and modules to manage load balancers, we can create a playbook to perform a rolling update

The variable serial controls the number of servers that are concurrently updated

Rolling update in AWS

---
- hosts: web
  serial: 3
  pre_tasks:

      - name: Gathering ec2 facts
        action: ec2_facts

      - name: Instance de-register
        local_action:
            module: ec2_elb
            instance_id: "{{ ansible_ec2_instance_id }}"
            state: 'absent'
  roles:

      - role_that_updates

  post_tasks:

      - name: Instance register
        local_action:
            module: ec2_elb
            instance_id: "{{ ansible_ec2_instance_id }}"
            ec2_elbs: "{{ item }}"
            state: 'present'
        with_items: ec2_elbs

ansible-playbook -i ec2.py rolling-update.yml

rolling-update.yml

More advanced topics

  • Complex templating, filters and variable manipulation
  • Asynchronous actions
  • Local playbooks and delegation
  • Ansible pull mode
  • Using ansible-vault to encrypt data
  • Development of new modules
  • ...

Further reading

Great documentation at docs.ansible.com

Good books:

Happy hacking!

Introduction to Ansible

By Alejandro Guirao Rodríguez

Introduction to Ansible

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