Ansible

What is Ansible?

Started in 2012
More than 600 contributors
Orchestration Engine
- Configuration Management
- Application Deployment
- Continuous Delivery

Ansible Commands

ansible: Low level command to execute simple Ansible resources
ansible-playbook: Tool to run Ansible Playbooks
ansible-pull: Tool to pull remote Ansible configurations and run the playbooks locally
ansible-doc: Tool to show documentation on Ansible modules
ansible-galaxy: Tool to manage roles from Ansible Galaxy, a shared repository of Ansible roles maintained by the community

Ansible Components

Modules: Python-driven code that actually does the work in Ansible and executed on the remote host.
Inventory: Defines how Ansible with interact with remote hosts and defines hosts, groups of hosts in a logical manner. You also define host and group variables inside the inventory.
Playbooks: Ansible's configuration, deployment and orchestration language that uses the YAML format.
Roles: Reusable list of tasks and playbooks typically centered in a specific task, such as deploying a web service

Modules

Python code that is executed on the remote host
Always returns JSON data
Controls and manage system resources
Core Modules: Shipped and maintained by Ansible
Extras Modules: Shipped with Ansible, but maintained by the community

Modules Categories

Cloud	Clustering	Commands
Database	Files	Inventory
Messaging	Monitoring	Network
Notification	Packaging	Source Control
System	Utilities	Web Infra
Windows

Ansible Module Index

Module documentation:

ansible-doc file

Files Module: copy

The [copy] module copies a file on the local box to remote locations. Use the [fetch] module to copy files from remote locations to the local box. If you need variable interpolation in copied files, use the [template] module.

# Simple file copy
- copy: src=/srv/myfiles/foo.conf
        dest=/etc/foo.conf
        owner=foo
        group=foo
        mode=0644

# Copy a new "sudoers" file into place, after passing validation
# with visudo
- copy: src=/mine/sudoers
        dest=/etc/sudoers
        validate='visudo -cf %s'

Source Control Module: git

Manage 'git' checkouts of repositories to deploy files or software.

- git: repo=git://foosball.example.org/path/to/repo.git
       dest=/srv/checkout
       version=release-0.22

Facts

Facts is a core module that gathers useful variables about remote hosts
All Ansible facts are prefixed with ansible_
If factor (Puppet) or ohai (Chef) is installed, Ansible will gather those folks too and prefix them respectively

# Display facts from all hosts and store them indexed by I(hostname) at C(/tmp/facts).
ansible all -m setup --tree /tmp/facts

# Display only facts regarding memory found by ansible on all hosts and output them.
ansible all -m setup -a 'filter=ansible_*_mb'

# Display only facts returned by facter.
ansible all -m setup -a 'filter=facter_*'

# Display only facts about certain interfaces.
ansible all -m setup -a 'filter=ansible_eth[0-2]'

Inventory

Contains all the hosts known to Ansible
Also contains variables
Can be flat files or dynamic via scripts
Default location /etc/ansible/hosts

mail.example.com

[webservers]
foo.example.com
bar.example.com

[dbservers]
one.example.com
two.example.com
three.example.com

Inventory communication variables

Variable	Description
`ansible_user`	The default ssh user name to use
`ansible_host`	The name or IP of the host to connect to, if different from the alias you wish to give to it.
`ansible_port`	The ssh port number, if not 22

wordpress-server ansible_host=140.211.168.106 ansible_user=centos

List of other parameters

Inventory Examples

# Range of hosts using patterns
[webservers]
www[01:50].example.com

# Host variables
[atlanta]
host1 http_port=80 maxRequestsPerChild=808
host2 http_port=303 maxRequestsPerChild=909

# Group Variables
[atlanta]
host1
host2

[atlanta:vars]
ntp_server=ntp.atlanta.example.com
proxy=proxy.atlanta.example.com

Groups of groups, and group variables

Using the :children suffix allows for groups of groups.

[atlanta]
host1
host2

[raleigh]
host2
host3

[southeast:children]
atlanta
raleigh

[southeast:vars]
some_server=foo.southeast.example.com
halon_system_timeout=30
self_destruct_countdown=60
escape_pods=2

[usa:children]
southeast
northeast
southwest
northwest

Patterns

Patterns in Ansible decide which hosts to manage

All hosts in the inventory: all or *
Specific host or group: host1, webservers
Wildcard: 192.168.1.*
OR: host1:host2, webservers:dbservers
NOT: webservers:dbservers:!production
AND: webservers:dbservers:&staging
REGEX: ~(web|db).*\.example\.com

Pattern Examples

# Run this on the webservers group
ansible webservers -m service -a "name=httpd state=restarted"

# Target all hosts
all
*

# Target specific host or a set of hosts
one.example.com
one.example.com:two.example.com
192.168.1.50
192.168.1.*

# Target groups or one or more groups. Colon indicates OR
webservers
webservers:dbservers

# Exclude groups
webservers:!phoenix

# Intersection of two groups. Hosts would need to be in both groups
# to run.
webservers:&staging

# Combo!
# All machines in the groups ‘webservers’ and ‘dbservers’ are to be
# managed if they are in the group ‘staging’ also, but the machines
# are not to be managed if they are in the group ‘phoenix
webservers:dbservers:&staging:!phoenix

Dynamic Inventory

Using external databases or APIs to manage your Ansible infrastructure
Cloud provider, LDAP, Cobbler, or another CM Database

Openstack Example

wget https://raw.githubusercontent.com/ansible/ansible/devel/contrib/inventory/openstack.py
chmod +x openstack.py
ansible -i openstack.py all -m ping

See the Ansible OpenStack Example for more information.

Ansible CLI

# Usage: ansible host-pattern -m [module] \
#   -a [module-options] [command-flags]

# Ping all hosts with one line output
ansible all -m ping -o
# Run setup module gathering facts from the host
ansible demo -m setup
# Run an ad-hoc reboot command
ansible foo.example.com -a “/usr/sbin/reboot”
# Copy a file using the file module
ansible demo -m file -a "dest=/srv/foo/a.txt mode=600" -o
# Install httpd using the yum module
ansible demo-one -m yum -a "name=httpd state=installed"
# Start httpd using the service module
ansible demo-one -m service -a "name=httpd state=started"

Playbooks

Expressed in YAML
Usually composed of one or more "plays" in a list
Allows for multi-machine deployment orchestration
Lists tasks to execute
Tasks are usually one module
Include variables and handlers
Idempotent

Playbook Example

- hosts: http
  remote_user: user
  sudo: yes
  vars:
   in_ports:
   - 80
 tasks:
   - name: install httpd
     action: yum name=httpd state=latest

   - name: copy httpd.conf
     action: template
        src=httpd.conf.j2
        dest=/etc/httpd/conf/httpd.conf
        owner=root
        group=root
        mode=0644
        seuser="system_u"
        setype="httpd_config_t"
        backup=yes
     notify:
     - restart httpd

Handlers

Basic event system that can be triggered from tasks
Events can only be triggered once
Handlers usually be used to restart services

- name: template configuration file
  template: src=template.j2 dest=/etc/foo.conf
  notify:
     - restart memcached
     - restart apache

# Handlers
- name: restart memcached
  service: name=memcached state=restarted
- name: restart apache
  service: name=apache state=restarted

Roles

Reusable list of tasks
Usually has a single goal (i.e. deploy apache)
Reusable

- hosts: demo
  gather_facts: False
  connection: local
  serial: 1
  vars:
   in_ports:
   - 80
  roles:
  - httpd
  - mysql
  - iptables

Templates

Jinja2 templating engine
Use of variables
Loops, conditionals, filters, etc

# Build an apache Proxy config
< Proxy balancer://{{ balancer_name }}>
{% for host in groups['demo-web'] %}
  BalancerMember http://{{ hostvars[host].ansible_eth1.ipv4.address }}
{% endfor %}
  Order allow,deny
  Allow from all
< /Proxy>

`ansible-playbook`

Execute a playbook
Setting up a whole environment or set of hosts

Usage: ansible-playbook playbook.yml -i inventory

Best Practices

production      # inventory file for production servers
stage           # inventory file for stage environment

group_vars/
   group1       # here we assign variables to particular groups
   group2       # ""
host_vars/
   hostname1    # if systems need specific variables, put them here
   hostname2    # ""

site.yml        # master playbook
webservers.yml  # playbook for webserver tier
dbservers.yml   # playbook for dbserver tier

roles/
    common/             # this hierarchy represents a "role"
        tasks/          #
            main.yml    #  <-- tasks file can include smaller files if warranted
        handlers/       #
            main.yml    #  <-- handlers file
        templates/      #  <-- files for use with the template
                        #      resource
            ntp.conf.j2 #  <------- templates end in .j2
        files/          #
            bar.txt     #  <-- files for use with the copy resource
            foo.sh      #  <-- script files for use with the script
                        #      resource
        vars/           #
            main.yml    #  <-- variables associated with this role

    webtier/            # same kind of structure as "common" was
                        # above, done for the webtier role
    monitoring/         # ""
    fooapp/             # ""

Variables

Variables allow you to deal with differences between systems
Valid names should be letters, numbers, and underscores and always start with a letter

playbook.yml
- hosts: webservers
  template: src=foo.cfg.j2 dest={{ remote_install_path }}/foo.cfg
  vars:
    http_port: 80

Templates

My amp goes to {{ max_amp_value }}

YAML Gotchas

Sometimes YAML is quirky so read up on the YAML Syntax

For example, this won't work:

- hosts: app_servers
  vars:
      app_path: {{ base_path }}/22

However this will work fine:

- hosts: app_servers
  vars:
       app_path: "{{ base_path }}/22"

Installing Ansible

# EPEL repo
yum install ansible

# Available through a PPA
apt-get install ansible

# Also available via pip
pip install ansible

What is Ansible?

Ansible Commands

Ansible Components

Modules

Modules Categories

Files Module: copy

Source Control Module: git

Facts

Inventory

Inventory communication variables

Inventory Examples

Groups of groups, and group variables

Patterns

Pattern Examples

Dynamic Inventory

Ansible CLI

Playbooks

Playbook Example

Handlers

Roles

Templates

ansible-playbook

Best Practices

Variables

YAML Gotchas

Installing Ansible

Resources

`ansible-playbook`