Ansible Learning Notes

GeekerHWH | Feb 24, 2024 min read
Ansible Learning Notes

Prefix

This page is my own notes during learning Ansible, and can’t be alternative to official documents. All knowledge comes from Udemy course: Ansible for the Absolute Beginner - Hands-On - DevOps

Why Ansible

the usages of ansible:

  • Provisioning
  • Configuration Management
  • Continuous Delivery / Continuous Integration
  • Application Deployment
  • Security Compliance

Ansible vs Scripts

scriptsAnsible
TimeSimple
Coding SkillsPowerful
MaintenanceAgentless

“Agentless” means you don’t need to install any agent software in the target machines to work with ansible.

setup

set up ansible controller

vim /etc/hostname
vim /etc/hostfile

set up ansible targets 1 and 2

install

debian as an example, for other distros please check the Instruction for Installing

sudo apt install ansible
# ansible --version # check if installation was completed

inventoy

inventoy is used for configuration for the controller, telling it how to connect to the targets

default address: /etc/ansible/host

[web_servers]
master_server ansible_host=master.server.com
slave_server ansible_host=192.168.1.11

[db_servers]
db1 ansible_host=192.168.1.20

Basic parameters

Inventory Parameters:

  • ansible_host: the domain or ip addr of the host
  • ansible_connection: connection protocol (e.g. ssh/winrm/localhost)
  • ansible_port: connection port 22/5986
  • ansible user: username root/administrator
  • ansible_ssh_pass: SSH Password

Commands

ansible target1 -m ping -i inventory.txt # -m module -i input
ansible <host> -a <command>
ansible <host> -m <mmodule>

ansible config

default address: /etc/ansible/ansible.cfg

Ansible Playbooks

Playbook is a single YAML file

  • Play: Defines set of activities(tasks) to be run on hosts
    • Task: An action to be performed on the host
      • Execute a command
      • Run a script
      • Install a package
      • Shutdown/Restart
ansible-playbook <playbook_path> -i <inventoy_name>

Modules

  • System
    • User
    • Group
    • Hostname
    • Iptables
    • Lvg
    • Lvol
    • Make
    • Mount
    • Ping
    • Timezone
    • Systemd
    • Service
  • Commands
    • Command
    • Expect
    • Raw
    • Script
    • Shell
  • Files
    • Acl
    • Archive
    • Copy
    • File
    • Find
    • Lineinfile
    • Replace
    • Stat
    • Template
    • Unarchive
  • Database
    • Mongodb
    • Mssql
    • Mysql
    • Postgresql
    • more…
  • Cloud
    • Amazon
    • Atomic
    • Azure
    • Centrylink
    • more…
  • Windows
    • Win_copy
    • Win_command
    • Win_domain
    • Win_file
    • more…
  • more…

Idempotency: An operation is idempotent if the result of performing it once is exactly the same as the result of performing it repeatedly without any intervening actions.

Variables

stores the information that varies with each host.

you can define variables in a file with same name of the host

single variable should be included in ', e.g.

  • ‘{{variable}}’
  • somthing {{variable}} somthing

Conditionals

check examples

Loops

check examples

Examples

# simple variable use case
-
    name: Add DNS server to resolv.conf
    hosts: localhost
        vars:
            dns_server: 10.1.250.10
        tasks:
            - lineinfile:
                path: /etc/resolv.conf
                line: 'nameserver {{ dns_server }}'

# simple conditional use case
-
  name: Install NGINX
  hosts: all
  tasks: 
  - name: Install NGINX on Debian
    apt:
      name: nginx
      state: present
    when: ansible_os_family == "Debian"   and
          ansible_distribution_version == "16.04"
  - name: INstall NGINX on Redhat
    yum:
      name: nginx
      state: present
    when: ansible_os_family == "RedHat"   or
          ansible_os_family == "SUSE"

# conditional in loops
-
  name: Install Softwares
  hosts: all
  vars:
    packages:
      - name: nginx
        required: True
      - name: mysql
        required: True
      - name: apache
  tasks:
  - name: Install "{{ item.name }}" on Debian
    apt:
      name: "{{ item.name }}"
      state: present
    
    when: item.required == True
    loop: "{{ packages }}"

# conditional and register
-
  name: Check status of httpd and email if its down
  hosts: all
  tasks:
    - command: service httpd status
      register: result

    - mail:
        to: admin@company.com
        subject: HTTPD Service Alert
        body: Httpd Service is down
        when: result.stdout.find('down') != -1

#loops
-
  name: Create users
  hosts: localhost
  tasks:
  - user: name= '{{item.name}}' state=present uid= '{{irem.uid}}'
    loop:
      - name: joe
        uid: 1010
      - name: george
        uid: 1011
      - name: mike
        uid: 1012

Ansible Role

the primary purpose of role is to make your tasks code reusable

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