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Written by Oleksandr Gavenko (AKA gavenkoa), compiled on 2020-11-21 from rev ebbf146d86c1+.

Ansible

Debugging Ansible

Pass -vvv to Ansible utilities:

ansible -vvv ...
ansible-playbook -vvv ...

To debug connection use -vvvv:

ansible -vvvv ...

Print variable value with task debug:

- debug: var=ansible_host
- debug:
    var: ansible_host
- debug:
    msg: "host is {{ ansible_host }}"

To debug Python modules set ANSIBLE_KEEP_REMOTE_FILES to 1 (it causes Ansible to leave the exact copy of the Python scripts it executed on the target machine):

ANSIBLE_KEEP_REMOTE_FILES=1  ansible ...

There is debugger keyword that triggers debugger, see Ansible Debugger

To activate debugger on task:

- name: Execute a command
  command: false
  debugger: on_failed

To activate debugger in ansible.cfg:

[defaults]
enable_task_debugger = True

To activate debugger via env var:

ANSIBLE_ENABLE_TASK_DEBUGGER=True ansible-playbook -i hosts site.yml

Use ansible-lint:

$ sudo apt install ansible-lint
$ ansible-lint site.yml
https://docs.ansible.com/ansible/latest/network/user_guide/network_debug_troubleshooting.html
Network Debug and Troubleshooting Guide.
https://stackoverflow.com/questions/42417079/how-to-debug-ansible-issues
How to debug Ansible issues?

Bash completion

https://github.com/ansible/ansible/issues/36397
Provide bash-completion script for ansible commands.
https://docs.ansible.com/ansible/devel/installation_guide/intro_installation.html#shell-completion
As of Ansible 2.9 shell completion of the ansible command line utilities is available and provided through an optional dependency called argcomplete.

Ansible language

https://docs.ansible.com/ansible/latest/user_guide/playbooks_module_defaults.html
Module defaults.
https://docs.ansible.com/ansible/latest/reference_appendices/playbooks_keywords.html
Reserved keywords.
https://docs.ansible.com/ansible/latest/user_guide/intro_patterns.html
Patterns: targeting hosts and groups.
https://docs.ansible.com/ansible/latest/network/getting_started/first_inventory.html
Using aliases & groups for hosts.
https://docs.ansible.com/ansible/latest/user_guide/playbooks_error_handling.html
Error handling in playbooks

Variables:

https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html
Using Variables. Precedence.
https://docs.ansible.com/ansible/latest/reference_appendices/config.html
Ansible Configuration Settings.
https://docs.ansible.com/ansible/latest/reference_appendices/special_variables.html
Magic variables.
https://docs.ansible.com/ansible/latest/user_guide/playbooks_vars_facts.html
Discovering variables: facts and magic variables.
https://docs.ansible.com/ansible/latest/collections/ansible/builtin/set_fact_module.html
ansible.builtin.set_fact – Set host facts from a task.

Inventory:

https://docs.ansible.com/ansible/latest/collections/ansible/builtin/generator_inventory.html
Uses Jinja2 to construct hosts and groups from patterns.

Collections:

https://docs.ansible.com/ansible/latest/user_guide/collections_using.html
Using collections.
https://docs.ansible.com/ansible/2.10/collections/index.html
Collection Index.

Inclusion:

https://docs.ansible.com/ansible/latest/collections/ansible/builtin/include_module.html
Include a play or task list.

Filters:

https://jinja.palletsprojects.com/en/master/templates/
Jinja template language. List of Builtin Filters.
https://docs.ansible.com/ansible/latest/user_guide/playbooks_filters.html
Using filters to manipulate data.

Execution:

https://docs.ansible.com/ansible/latest/user_guide/playbooks_strategies.html
Controlling playbook execution: strategies and more.
https://docs.ansible.com/ansible/latest/plugins/strategy.html
Strategy Plugins.
https://docs.ansible.com/ansible/latest/user_guide/playbooks_delegation.html
Controlling where tasks run: delegation and local actions.
https://docs.ansible.com/ansible/latest/reference_appendices/general_precedence.html
Controlling how Ansible behaves: precedence rules.
https://docs.ansible.com/ansible/latest/user_guide/playbooks_handlers.html
Handlers: running operations on change.
https://docs.ansible.com/ansible/latest/collections/ansible/builtin/setup_module.html
ansible.builtin.setup – Gathers facts about remote hosts.

Search path

Files, templates, variables definitions are looked in files, templates, vars role / play directories first, then in the base directory for role / play.

https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html
You can also add group_vars/ and host_vars/ directories to your playbook directory. The ansible-playbook command looks for these directories in the current working directory by default. Other Ansible commands (for example, ansible, ansible-console, and so on) will only look for group_vars/ and host_vars/ in the inventory directory. If you want other commands to load group and host variables from a playbook directory, you must provide the --playbook-dir option on the command line. If you load inventory files from both the playbook directory and the inventory directory, variables in the playbook directory will override variables set in the inventory directory.
https://docs.ansible.com/ansible/latest/user_guide/playbook_pathing.html
Search paths in Ansible.

Templates

https://docs.ansible.com/ansible/latest/user_guide/playbooks_templating.html
Templating (Jinja2).

Execution

-f option controls forking: how many executors are started to perform tasks.

The way tasks are processed depends on strategy and serial.

strategy * serial can be defined on each hosts in a play:

- hosts: web
  strategy: free
  serial: 50%
- hosts: db
  strategy: linear
  serial: 1

Special variables

You can dump any variable by debug task in a playbook or using mudule:

ansible $host -m debug -a var=groups

Blocks

To avoid repetitive checks or to handle failures use block:

block:
- shell: echo do 1
- shell: echo do 2
when: not db_started
become: true
become_user: dba
rescue:
- shell: echo rollback
always:
- shell: echo notify

Collections

https://docs.ansible.com/ansible/latest/user_guide/collections_using.html
Using collections.

To install specific version use a colon and conditions with operators: ==, !=, >, >=, <, <= separated by comma:

ansible-galaxy collection install 'my_namespace.my_collection:>=1.0.0,<2.0.0'

Only one version of collection can be installed, if you want to update with different version use --force:

ansible-galaxy collection install google.cloud:=0.0.1
ansible-galaxy collection install --force google.cloud:=1.0.1