playbooks
Chapter 5
Learning to write Infrastructure as a Code
concepts
-
YAML PRIMER
-
ANATOMY OF A PLAYBOOK
-
Creating our first playbook
-
Adding Tasks and plays
even though ansible allows us to run ad hoc commands and modules on remote nodes, the real magic starts with the Playbooks
playbooks
Playbooks allow one to describe the state of the infrastructure and the sequence in which it is achieved ....
playbooks
as Infrastructure Code
which can then be version controlled and reused many times for many different environments
playbooks
playbook
Ansible
YAML
Playbooks are written in
YAML
with intention of being both
Human Readable
as well as
machine Readable
YAML primer
-
Begin/END Tags
-
Lists
-
Dictionaries
-
Indentation
-
Line Foldings
begin tag
All YAML files to begin with three dashes ---
---
# This is a YAML Document
- list item 1
- list item 2
...and end with three dots ...
even though its not a must, its a good coding practice to follow this
lists
Ansible plays contain list of items e.g. tasks, hosts, options
---
- name
hosts
become
tasks
- package
- file
- user
...lists and dictionaries
Ansible plays contain list of items e.g. tasks, hosts, options
---
- name: configure app hosts
hosts: app
become: true
tasks
- package: name=apache state=present
- copy: name=ntp.conf src=files/ntp.conf dest=/etc/ntp.conf
- user: name=dojo state=present
...with key value pairs commonly known as hashes or dictionaries
all members of the list are at the same indentation level
Style 1
---
- name: configure app hosts
hosts: app
become: true
tasks
- package: name=apache state=present
- copy: >
name=ntp.conf
src=files/ntp.conf
dest=/etc/ntp.conf
- user: |
name=dojo
uid=5001
home=/home/dojo
state=present
...> |
---
- name: configure app hosts
hosts: app
become: true
tasks
- package: name=apache state=present
- copy:
name: ntp.conf
src: files/ntp.conf
dest: /etc/ntp.conf
- user:
name: dojo
uid: 5001
home: /home/dojo
state: present
...style 2
:
YAML LINTER
http://www.yamllint.com/
EXERCISE
Read about yaml: https://en.wikipedia.org/wiki/YAML
Create a yaml file
src: http://www.india.com/buzz/this-precise-grocery-shopping-list-of-an-indian-wife-for-her-husband-will-make-you-laugh-like-crazy-2496164/
Anatomy of a playbook
plays
WHICH hosts
do WHAT
describe
TASKS
inventory
modules
hosts, vars, become
plays
name
hosts
become
vars
tasks
plays
name
hosts
become
vars
tasks
- name: App Server Configurations
hosts: app
become: true
become_user: admin
become_method: sudo
vars:
apache_port = 8080
max_conections = 4000
ntp_conf = /etc/ntp.conf
tasks:
- name: create app user
user: name=app state=present uid=5002
- name: install git
yum: name=tree state=present
become
think of sudo
used to run tasks as a different user / become another user
introduced in version 1.9 and supercedes sudo / su
supports sudo, su, pfexec, doas, pbrun, dzdo, ksu and others
tasks
Components of Plays which define the desired state of / action taken on a system entity
there is a 1-1 mapping between the task and the system entity managed
tasks invoke modules which are encapsulated procedures to take actions.
modules are also called as task plugins
task styles
- name: install ntp package yum: name=ntp state=present
- yum: name=ntp state=present
multi line tasks
- name: create dojo user user: > name=dojo uid=5001 home=/home/dojo state=present
- name: create dojo user user: | name=dojo uid=5001 home=/home/dojo state=present
- name: create dojo user user: name: dojo uid: 5001 home: /home/dojo state: present
playbook example
---
- name: Base Configurations for ALL hosts
hosts: all
become: true
tasks:
- name: create admin user
user:
name: admin
state: present
uid: 5001
- name: remove dojo
user:
name: dojo
state: absent
- name: install tree
yum:
name: tree
state: present
- name: install ntp
yum:
name: ntp
state: present
- name: start ntp service
service:
name: ntpd
state: started
enabled: yes
- name: App Server Configurations
hosts: app
become: true
tasks:
- name: create deploy user
user:
name: deploy
state: present
uid: 5003
- name: install git
yum:
name: git
state: present
play1
play2
GE
Writing our first Playbook
cd ansible-bootcamp-code/chap5
ansible all -m pingswitch to chap5 code and validate
You have to create a playbook for base systems configuration. Common configurations for all hosts are,
GE
-
admin user should be present with uid 5001
-
user dojo should not have an account on any host
-
install tree utility
-
install ntp
Problem Statement
on all systems which belong to prod group in the inventory
Lets now create systems.yml file and start adding our first play
---
- name: Base Configurations for ALL hosts
hosts: all
become: true
tasks:
- name: create admin user
user:
name: admin
state: present
uid: 5001
- name: remove dojo
user:
name: dojo
state: absent
- name: install tree
package:
name: tree
state: present
- name: install ntp
package:
name: ntp
state: present
file: systems.yml
GE
GE
validate yaml
ansible-playbook systems.yml --syntax-checkSyntax Check
Exercise: Break the syntax, run playbook with --syntax check again, and learn how it works.
GE
http://www.yamllint.com
validate yaml
Another way to validate syntax
ansible playbook utility
# ansible-playbook --help
Usage: ansible-playbook playbook.yml
Options:
--ask-vault-pass ask for vault password
-C, --check don't make any changes; instead, try to predict some
of the changes that may occur
-D, --diff when changing (small) files and templates, show the
differences in those files; works great with --check
-e EXTRA_VARS, --extra-vars=EXTRA_VARS
set additional variables as key=value or YAML/JSON
--flush-cache clear the fact cache
--force-handlers run handlers even if a task fails
-f FORKS, --forks=FORKS
specify number of parallel processes to use
(default=5)
-h, --help show this help message and exit
-i INVENTORY, --inventory-file=INVENTORY
specify inventory host path (default=myhosts.ini) or
comma separated host list.
-l SUBSET, --limit=SUBSET
further limit selected hosts to an additional pattern
--list-hosts outputs a list of matching hosts; does not execute
anything else
--list-tags list all available tags
--list-tasks list all tasks that would be executedansible-playbook --help
listing hosts and tasks
GE
ansible-playbook systems.yml --list-tasksList Hosts to which this playbook applies
ansible-playbook systems.yml --list-hostsList Tasks
ansible-playbook systems.yml --list-tagsList Tags
Apply
root@control:/workspace/ansible-bootcamp-code/chap5# ansible-playbook systems.yaml
[WARNING]: Found both group and host with same name: db
[WARNING]: Found both group and host with same name: lb
PLAY [Base Configurations for ALL hosts] **************************************************************************************
TASK [Gathering Facts] ********************************************************************************************************
ok: [db]
ok: [lb]
ok: [app1]
ok: [app2]
[DEPRECATION WARNING]: Distribution Ubuntu 18.04 on host localhost should use /usr/bin/python3, but is using /usr/bin/python
for backward compatibility with prior Ansible releases. A future Ansible release will default to using the discovered platform
python for this host. See https://docs.ansible.com/ansible/2.9/reference_appendices/interpreter_discovery.html for more
information. This feature will be removed in version 2.12. Deprecation warnings can be disabled by setting
deprecation_warnings=False in ansible.cfg.
ok: [localhost]
TASK [create admin user] ******************************************************************************************************
changed: [app1]
changed: [app2]
changed: [lb]
changed: [db]
changed: [localhost]
TASK [remove dojo] ************************************************************************************************************
ok: [localhost]
ok: [app1]
ok: [lb]
ok: [app2]
ok: [db]
TASK [install tree] ***********************************************************************************************************
changed: [app2]
changed: [db]
changed: [app1]
changed: [lb]
[WARNING]: Updating cache and auto-installing missing dependency: python-apt
changed: [localhost]
TASK [install ntp] ************************************************************************************************************
ok: [app1]
ok: [app2]
changed: [lb]
changed: [db]
changed: [localhost]
PLAY RECAP ********************************************************************************************************************
app1 : ok=5 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
app2 : ok=5 changed=2 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
db : ok=5 changed=3 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
lb : ok=5 changed=3 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
localhost : ok=5 changed=3 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0
root@control:/workspace/ansible-bootcamp-code/chap5# ansible-playbook systems.yamladding a new task
GE
Lets now add a new task to systems.yml to
-
start ntpd service
---
- name: Base Configurations for ALL hosts
hosts: all
become: true
tasks:
- name: create admin user
user:
name: admin
state: present
uid: 5001
- name: remove dojo
user:
name: dojo
state: absent
- name: install tree
package:
name: tree
state: present
- name: install ntp
package:
name: ntp
state: present
- name: start ntp service
service:
name: ntpd
state: started
enabled: yes
File: systems.yml
adding a new task
GE
TASK [start ntp service] ******************************************************************************************************
fatal: [localhost]: FAILED! => {"changed": false, "msg": "Could not find the requested service ntpd: host"}
fatal: [lb]: FAILED! => {"changed": false, "msg": "Could not find the requested service ntpd: host"}
fatal: [db]: FAILED! => {"changed": false, "msg": "Could not find the requested service ntpd: host"}
fatal: [app1]: FAILED! => {"changed": false, "msg": "Could not find the requested service ntpd: host"}
fatal: [app2]: FAILED! => {"changed": false, "msg": "Could not find the requested service ntpd: host"}
error handling
ansible-playbook systems.yml
status = failed
GE
root@control:/workspace/chap5# ansible-playbook systems.yml --step
PLAY [Base Configurations for ALL hosts] ***************************************
Perform task: TASK: setup (N)o/(y)es/(c)ontinue: y
TASK [setup] *******************************************************************
y
ok: [app1]
ok: [db]
ok: [app2]
ok: [lb]
Perform task: TASK: create admin user (N)o/(y)es/(c)ontinue:
TASK [create admin user] *******************************************************
yok: [app2]
ok: [app1]
ok: [db]
ok: [lb]
Perform task: TASK: install tree (N)o/(y)es/(c)ontinue: y
TASK [install tree] ************************************************************
ok: [app2]
ok: [lb]
ok: [app1]
ok: [db] Step by step execution
ansible-playbook systems.yml --step
GE
You could also do step by step execution of tasks by using --step option
fixing error
GE
service : ntpd => ntp
TASK [install ntpd] ************************************************************************************************************
fatal: [app1]: FAILED! => {"changed": false, "failures": ["No package ntpd available."], "msg": "Failed to install some of the specified packages", "rc": 1, "results": []}
fatal: [lb]: FAILED! => {"changed": false, "failures": ["No package ntpd available."], "msg": "Failed to install some of the specified packages", "rc": 1, "results": []}
fatal: [app2]: FAILED! => {"changed": false, "failures": ["No package ntpd available."], "msg": "Failed to install some of the specified packages", "rc": 1, "results": []}
fatal: [db]: FAILED! => {"changed": false, "failures": ["No package ntpd available."], "msg": "Failed to install some of the specified packages", "rc": 1, "results": []}
fatal: [localhost]: FAILED! => {"ansible_facts": {"pkg_mgr": "apt"}, "changed": false, "msg": "value of state must be one of: absent, build-dep, fixed, latest, present, got: installed"}
PLAY Root Cause : NTP service name is ntp and not ntpd on Ubuntu
---
- name: Base Configurations for ALL Hosts
hosts: all
become: true
tasks:
- name: create admin user
user:
name: admin
state: present
uid: 5001
- name: remove dojo
user:
name: dojo
state: absent
- name: install tree
apt:
name: tree
state: present
- name: install ntp
apt:
name: ntp
state: present
- name: start ntp service
service:
name: ntp
state: started
File: systems.yml
fixing error
GE
ntpd => ntp
adding second play
GE
Add a new play to existing playbook which will,
-
create a deploy user with uid 5003
-
install git
Problem Statement
on all app servers in the inventory
Setup app Servers
---
- name: Base Configurations for ALL hosts
hosts: all
become: true
tasks:
- name: create admin user
user:
name: admin
state: present
uid: 5001
- name: remove dojo
user:
name: dojo
state: absent
- name: install tree
package:
name: tree
state: present
- name: install ntp
package:
name: ntp
state: present
- name: start ntp service
service:
name: ntp
state: started
enabled: yes
- name: App Server Configurations
hosts: app
become: true
tasks:
- name: create deploy user
user:
name: deploy
state: present
uid: 5003
- name: install git
yum:
name: git
state: present
adding second play
File: systems.yml
play1
play2
GE
PLAY [Base Configurations for ALL hosts] ***************************************
TASK [setup] *******************************************************************
ok: [localhost]
ok: [192.168.61.14]
ok: [192.168.61.13]
ok: [192.168.61.12]
ok: [192.168.61.11]
TASK [create admin user] *******************************************************
ok: [192.168.61.14]
ok: [localhost]
ok: [192.168.61.13]
ok: [192.168.61.12]
ok: [192.168.61.11]
TASK [remove dojo] *************************************************************
ok: [192.168.61.14]
ok: [192.168.61.12]
ok: [192.168.61.11]
ok: [localhost]
ok: [192.168.61.13]
TASK [install tree] ************************************************************
ok: [192.168.61.11]
ok: [192.168.61.12]
ok: [localhost]
ok: [192.168.61.13]
ok: [192.168.61.14]
TASK [install ntp] *************************************************************
ok: [192.168.61.12]
ok: [192.168.61.13]
ok: [192.168.61.14]
ok: [192.168.61.11]
ok: [localhost]
TASK [start ntp service] *******************************************************
ok: [192.168.61.13]
ok: [192.168.61.14]
ok: [localhost]
ok: [192.168.61.11]
ok: [192.168.61.12]
PLAY [App Server Configurations] ***********************************************
TASK [setup] *******************************************************************
ok: [192.168.61.13]
ok: [192.168.61.12]
TASK [create app user] *********************************************************
changed: [192.168.61.12]
changed: [192.168.61.13]
TASK [install git] *************************************************************
ok: [192.168.61.13]
ok: [192.168.61.12]
PLAY RECAP *********************************************************************
192.168.61.11 : ok=6 changed=0 unreachable=0 failed=0
192.168.61.12 : ok=9 changed=1 unreachable=0 failed=0
192.168.61.13 : ok=9 changed=1 unreachable=0 failed=0
192.168.61.14 : ok=6 changed=0 unreachable=0 failed=0
localhost : ok=6 changed=0 unreachable=0 failed=0apply Playbook
ansible-playbook systems.yml
GE
GE
You have to limit execution of the tasks
-
only to app servers
Problem Statement
irrespective of host groups playbook defines
PLAY [Base Configurations for ALL hosts] ***************************************
TASK [setup] *******************************************************************
ok: [localhost]
ok: [192.168.61.14]
ok: [192.168.61.13]
ok: [192.168.61.12]
ok: [192.168.61.11]
TASK [create admin user] *******************************************************
ok: [192.168.61.14]
ok: [localhost]
ok: [192.168.61.13]
ok: [192.168.61.12]
ok: [192.168.61.11]
TASK [remove dojo] *************************************************************
ok: [192.168.61.14]
ok: [192.168.61.12]
ok: [192.168.61.11]
ok: [localhost]
ok: [192.168.61.13]
TASK [install tree] ************************************************************
ok: [192.168.61.11]
ok: [192.168.61.12]
ok: [localhost]
ok: [192.168.61.13]
ok: [192.168.61.14]
TASK [install ntp] *************************************************************
ok: [192.168.61.12]
ok: [192.168.61.13]
ok: [192.168.61.14]
ok: [192.168.61.11]
ok: [localhost]
TASK [start ntp service] *******************************************************
ok: [192.168.61.13]
ok: [192.168.61.14]
ok: [localhost]
ok: [192.168.61.11]
ok: [192.168.61.12]
PLAY [App Server Configurations] ***********************************************
TASK [setup] *******************************************************************
ok: [192.168.61.13]
ok: [192.168.61.12]
TASK [create app user] *********************************************************
changed: [192.168.61.12]
changed: [192.168.61.13]
TASK [install git] *************************************************************
ok: [192.168.61.13]
ok: [192.168.61.12]
PLAY RECAP *********************************************************************
192.168.61.11 : ok=6 changed=0 unreachable=0 failed=0
192.168.61.12 : ok=9 changed=1 unreachable=0 failed=0
192.168.61.13 : ok=9 changed=1 unreachable=0 failed=0
192.168.61.14 : ok=6 changed=0 unreachable=0 failed=0
localhost : ok=6 changed=0 unreachable=0 failed=0limiting execution
ansible-playbook systems.yml --limit app
GE
https://github.com/schoolofdevops/html-sample-app.gitLab Exercise 2: Disable Facts Gathering
-
Run ansible playbook and observe the output
-
Add the following configuration parameter to ansible.cfg gathering = explicit
-
Launch ansible playbook run again, observe the output and compare it with the previous run.
Lab Exercise 3:
While running playbook, execution should start at the following task onwards. Find out and use option applicable to ansible-playbook which will achieve this.
-
Task Name: "install ntp"