While you can write ansible modules in any language, most ansible modules are written in Python, and some of these
are important core ones.
By default Ansible assumes it can find a /usr/bin/python on your remote system that is a 2.X version of Python, specifically
2.4 or higher.
Setting of an inventory variable 'ansible_python_interpreter' on any host will allow Ansible to auto-replace the interpreter
used when executing python modules. Thus, you can point to any python you want on the system if /usr/bin/python on your
system does not point to a Python 2.X interpreter.
Some Linux operating systems, such as Arch, may only have Python 3 installed by default. This is not sufficient and you will
get syntax errors trying to run modules with Python 3. Python 3 is essentially not the same
language as Python 2. Ansible modules currently need to support older Pythons for users that still have Enterprise Linux 5 deployed, so they are not yet ported to run under Python 3.0. This is not a problem though as you can just install Python 2 also on a managed host.
Python 3.0 support will likely be addressed at a later point in time when usage becomes more mainstream.
Do not replace the shebang lines of your python modules. Ansible will do this for you automatically at deploy time.
Ansible by default gathers "facts" about the machines under management, and these facts can be accessed in Playbooks and in templates. To see a list of all of the facts that are available about a machine, you can run the "setup" module as an ad-hoc action::
ansible -m setup hostname
This will print out a dictionary of all of the facts that are available for that particular host.
A pretty common pattern is to iterate over a list of hosts inside of a host group, perhaps to populate a template configuration
file with a list of servers. To do this, you can just access the "$groups" dictionary in your template, like this::
{% for host in groups['db_servers'] %}
{{ host }}
{% endfor %}
If you need to access facts about these hosts, for instance, the IP address of each hostname, you need to make sure that the facts have been populated. For example, make sure you have a play that talks to db_servers::
- hosts: db_servers
tasks:
- # doesn't matter what you do, just that they were talked to previously.
Then you can use the facts inside your template, like this::
The "copy" module doesn't handle recursive copies of directories. A common solution to do this is to use a local action to call 'rsync' to recursively copy files to the managed servers.
Here is an example::
---
# ...
tasks:
- name: recursively copy files from management server to target
local_action: command rsync -a /path/to/files $inventory_hostname:/path/to/target/
Note that you'll need passphrase-less SSH or ssh-agent set up to let rsync copy without prompting for a passphase or password.
Great question! Documentation for Ansible is kept in the main project git repository, and complete instructions for contributing can be found in the docs README `viewable on GitHub <https://github.com/ansible/ansible/tree/devel/docsite/latest#readme>`_. Thanks!
