Resources attached to the Road To DevOps tutorial https://blog.noobtoroot.xyz/road-to-devops/

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Structures de contrôle

Facts

Variables délivrées par le système distant :
- Adresses IP
- Système d'exploitation
- ...

Facts - module setup

Liste des informations disponibles : module setup

$ ansible my-host -i ./hosts -m setup
my-host | SUCCESS => {
    "ansible_facts": {
        "ansible_all_ipv4_addresses": [
            "10.6.214.74"
        ],
        "ansible_all_ipv6_addresses": [
            "fe80::250:56ff:fe9d:1aaa"
        ],
        "ansible_architecture": "x86_64",
        ...

Facts pour la gestion multi-os

ansible_pkg_mgr : Le gestionnaire de paquets
ansible_os_family : La famille d'OS
ansible_distribution : Information détaillées sur la distribution

Gestionnaire de paquets

$ ansible my-host -i ./hosts -m setup | grep ansible_pkg_mgr
        "ansible_pkg_mgr": "yum",

Famille d'OS

$ ansible my-host -i ./hosts -m setup | grep ansible_family
        "ansible_os_family": "RedHat",

Distribution

$ ansible my-host -i ./hosts -m setup | grep ansible_distribution
        "ansible_distribution": "CentOS",
        "ansible_distribution_file_parsed": true,
        "ansible_distribution_file_path": "/etc/redhat-release",
        "ansible_distribution_file_variety": "RedHat",
        "ansible_distribution_major_version": "7",
        "ansible_distribution_release": "Core",
        "ansible_distribution_version": "7.5.1804",

Exemple d'aiguillage multi-OS

Arborescence du rôle

my-role
├── README.md
├── tasks
│   ├── CentOS.yaml -> RedHat.yaml
│   ├── Debian.yaml
│   ├── main.yaml
│   ├── RedHat.yaml
│   └── Ubuntu.yaml -> Debian.yaml
└── vars
    ├── CentOS-6.yaml
    ├── CentOS-7.yaml
    ├── Debian-8.yaml
    ├── Debian-9.yaml
    ├── RedHat-6.yaml
    ├── RedHat-7.yaml
    └── Ubuntu-16.yaml

my-role/tasks/main.yaml

- name: Add the OS specific variables
  include_vars: '{{ ansible_distribution }}-{{ ansible_distribution_major_version }}.yaml'

- include_tasks: '{{ansible_distribution}}.yaml'

Utilisation des conditionals

Action déclenchée de manière conditionnelle
(en fonction du résultat d’une variable).
Utilisation de when.

https://docs.ansible.com/ansible/playbooks_conditionals.html

Exemple

- hosts: web
  tasks:
    - name: Install Apache for CentOS system
      yum:
        name: httpd
        state: present
        update_cache: yes
      when:
        - ansible_os_family == "RedHat"   # sera joué sur RedHat et Centos
    - name: Install Apache for Ubuntu system
      apt:
        name: apache2
        state: present
        update_cache: yes
      when:
        - ansible_os_family == "Debian"   # sera joué sur Debian et Ubuntu

Chaque tâche cible une famille
de système d'exploitation précise.

$ ansible-playbook playbook.yaml -i ./hosts

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

TASK [setup] *****************************************************************
ok: [centos-vm]
ok: [ubuntu-vm]

TASK [Install Apache for CentOS system] **************************************
ok: [centos-vm]
skipping: [ubuntu-vm]

TASK [Install Apache for Ubuntu system] **************************************
skipping: [centos-vm]
ok: [ubuntu-vm]

PLAY RECAP *******************************************************************
centos-vm   : ok=2   changed=0   unreachable=0   failed=0
ubuntu-vm   : ok=2   changed=0   unreachable=0   failed=0

Les tâches sont exécutées ou non en fonction
de la famille du système d'exploitation.

Utilisation des loops

Boucles pour la réalisation d'actions répétitives.
Permet de faire plusieurs actions dans une seule tâche.
Création d'utilisateurs, installation de paquets, ...
Utilisation de ~~with-x~~ loop

https://docs.ansible.com/ansible/playbooks_loops.html

with-x

Paramètre | Type | Example d'utilisation

| - | - with_items | Array | To create a group of users, directories, or to install a list of packages with_nested | Nested loops | To create a list of MySQL users and grant them access to a group of databases with_dict | Hashes | To parse a dictionary of key-value pairs and create virtual hosts with_fileglobs |Files with pattern match | To parse a path and copy only those files that match a certain pattern with_together | S ets | To join two arrays as a set and to loop over it with_subelements | Hash sub element | To walk over the list of SSH keys and distribute them to a user with_sequence | Integer sequence | To loop a sequence of numbers with_random_choice | Random choice | To pick up items from the array in a random order with_indexed_items | Array with index | Array with an index and is useful when an index for items is required

Exemple avec with_items

- hosts: my-host
  tasks:
    - name: Add some users
      user:
        name: "{{ item }}"
        state: present
      with_items:
        - bob
        - alice
        - joe

Attention ! à partir d'Ansible 2.5 with-x n'est plus la méthode recommandé pour effectué des boucles.

$ ansible-playbook playbook.yaml -i ./hosts

PLAY [my-host] ***************************************************************

TASK [setup] *****************************************************************
ok: [my-host]

TASK [Add some users] ********************************************************
changed: [my-host] => (item=bob)
changed: [my-host] => (item=alice)
changed: [my-host] => (item=joe)

PLAY RECAP *******************************************************************
my-host   : ok=2   changed=1   unreachable=0   failed=0

La boucle a bien itéré sur les 3 utilisateurs.

Migration vers loop

A partir d'Ansible 2.5 with-x n'est plus la méthode recommandée pour effectuer des boucles.
La documentation sur les boucles propose une section pour aider à la migration de with-x vers loop.

https://docs.ansible.com/ansible/latest/user_guide/playbooks_loops.html

Exemple avec loop

- hosts: my-host
  tasks:
    - name: Add some users
      user:
        name: "{{ item }}"
        state: present
      loop:
        - bob
        - alice
        - joe

On remplace simplement with_items par loop.

$ ansible-playbook -i inventories/formation/hosts playbook.yaml

PLAY [my-host] ***************************************************************

TASK [Gathering Facts] *******************************************************
ok: [my-host]

TASK [Add some users] ********************************************************
changed: [my-host] => (item=bob)
changed: [my-host] => (item=alice)
changed: [my-host] => (item=joe)

PLAY RECAP *******************************************************************
my-host    : ok=2    changed=1    unreachable=0    failed=0

Le résultat final est strictement identique.

- hosts: my-host
  tasks:
    - name: Add some users
      user:
        name: "{{ item.name }}"
        state: present
        groups: "{{ item.groups }}"
      loop:
        - { name: 'bob', groups: 'wheel' }
        - { name: 'alice', groups: 'root' }
        - { name: 'joe', groups: 'root' }

En plus des strings , il est possible d'utiliser des hashes.

Itérer sur l'inventaire

- hosts: centos7
  tasks:
    - name: Iterate on hosts in the group all in the inventory
      debug:
        msg: "{{ item }}"
      loop: "{{ groups['all'] }}"   # on itère sur les machines du groupe all

$ ansible-playbook -i ./hosts playbook.yaml

PLAY [centos7] *****************************************************************

TASK [Iterate on hosts in the group all in the inventory] **********************
ok: [ansible-1] => (item=ansible-3) => {
    "msg": "ansible-3"
}
ok: [ansible-1] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-1] => (item=ansible-2) => {
    "msg": "ansible-2"
}
ok: [ansible-2] => (item=ansible-3) => {
    "msg": "ansible-3"
}
ok: [ansible-2] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-2] => (item=ansible-2) => {
    "msg": "ansible-2"
}

Chaque machine du Play (centos7) itère sur le groupe all.

Itérer sur le Play

- hosts: centos7
  tasks:
    - name: Iterate on all the hosts in the current play
      debug:
        msg: "{{ item }}"
      loop: "{{ ansible_play_batch }}"   # variable qui contient les machines du Play

$ ansible-playbook -i inventories/formation/hosts playbook.yaml

PLAY [centos7] *****************************************************************

TASK [Iterate on all the hosts in the current play] ****************************
ok: [ansible-1] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-1] => (item=ansible-2) => {
    "msg": "ansible-2"
}
ok: [ansible-2] => (item=ansible-1) => {
    "msg": "ansible-1"
}
ok: [ansible-2] => (item=ansible-2) => {
    "msg": "ansible-2"
}

Chaque machine du Play (centos7) itère
sur les machines du Play (centos7).

Travaux pratiques

TP Ansible : structures de contrôle

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