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ansible/docs/docsite/rst/reference_appendices/interpreter_discovery.rst
Matt Davis 4d3a6123d5
Python interpreter discovery (#50163) 
* Python interpreter discovery

* No longer blindly default to only `/usr/bin/python`
* `ansible_python_interpreter` defaults to `auto_legacy`, which will discover the platform Python interpreter on some platforms (but still favor `/usr/bin/python` if present for backward compatibility). Use `auto` to always use the discovered interpreter, append `_silent` to either value to suppress warnings.
* includes new doc utility method `get_versioned_doclink` to generate a major.minor versioned doclink against docs.ansible.com (or some other config-overridden URL)

* docs revisions for python interpreter discovery

(cherry picked from commit 5b53c0012ab7212304c28fdd24cb33fd8ff755c2)

* verify output on some distros, cleanup
2019-02-27 23:52:02 -08:00

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Interpreter Discovery

Most Ansible modules that execute under a POSIX environment require a Python interpreter on the target host. Unless configured otherwise, Ansible will attempt to discover a suitable Python interpreter on each target host the first time a Python module is executed for that host.

To control the discovery behavior:

  • for individual hosts and groups, use the ansible_python_interpreter inventory variable
  • globally, use the interpreter_python key in the [defaults] section of ansible.cfg

Use one of the following values:

auto_legacy : (default in 2.8)

Detects the target OS platform, distribution, and version, then consults a table listing the correct Python interpreter and path for each platform/distribution/version. If an entry is found, and /usr/bin/python is absent, uses the discovered interpreter (and path). If an entry is found, and /usr/bin/python is present, uses /usr/bin/python and issues a warning. This exception provides temporary compatibility with previous versions of Ansible that always defaulted to /usr/bin/python, so if you have installed Python and other dependencies at usr/bin/python on some hosts, Ansible will find and use them with this setting. If no entry is found, or the listed Python is not present on the target host, searches a list of common Python interpreter paths and uses the first one found; also issues a warning that future installation of another Python interpreter could alter the one chosen.

auto : (future default in 2.12)

Detects the target OS platform, distribution, and version, then consults a table listing the correct Python interpreter and path for each platform/distribution/version. If an entry is found, uses the discovered interpreter. If no entry is found, or the listed Python is not present on the target host, searches a list of common Python interpreter paths and uses the first one found; also issues a warning that future installation of another Python interpreter could alter the one chosen.

auto_legacy_silent

Same as auto_legacy, but does not issue warnings.

auto_silent

Same as auto, but does not issue warnings.

You can still set ansible_python_interpreter to a specific path at any variable level (for example, in host_vars, in vars files, in playbooks, etc.). Setting a specific path completely disables automatic interpreter discovery; Ansible always uses the path specified.