.. -*- mode: rst -*-

.. _client-tools-augeas:

========
 Augeas
========

The Augeas tool provides a way to use `Augeas
<http://www.augeas.net>`_ to edit files that may not be completely
managed.

In the simplest case, you simply tell Augeas which path to edit, and
give it a sequence of commands:

.. code-block:: xml

    <Path type="augeas" name="/etc/hosts" owner="root" group="root"
          mode="0644">
      <Set path="01/ipaddr" value="192.168.0.1"/>
      <Set path="01/canonical" value="pigiron.example.com"/>
      <Set path="01/alias[1]" value="pigiron"/>
      <Set path="01/alias[2]" value="piggy"/>
    </Path>

The commands are run in document order.  There's no need to do an
explicit ``save`` at the end.

These commands will be run if any of the paths do not already
have the given setting.  In other words, if any command has not
already been run, they will all be run.

So, if the first host already has all of the specified settings, then
that Path will verify successfully and nothing will be changed.  But
suppose the first host looks like this::

    192.168.0.1 pigiron.example.com pigiron

All that is missing is the second alias, ``piggy``.  The entire Augeas
script will be run in this case.  It's important, then, to ensure that
all commands you use are idempotent.  (For instance, the ``Move`` and
``Insert`` commands are unlikely to be useful.)

The Augeas paths are all relative to ``/files/etc/hosts``.

The Augeas tool understands a subset of ``augtool`` commands.  Valid
tags are: ``Remove``, ``Move``, ``Set``, ``Clear``, ``SetMulti``, and
``Insert``.  Refer to the official Augeas docs or the `Schema`_ below
for details on the commands.

The Augeas tool also supports one additional directive, ``Initial``,
for setting initial file content when a file does not exist.  For
instance, the ``Xml`` lens fails to parse a file that does not exist,
and, as a result, you cannot add content to it.  You can use
``Initial`` to circumvent this issue:

.. code-block:: xml

    <Path type="augeas" name="/etc/test.xml" lens="Xml"
          owner="root" group="root" mode="0640">
      <Initial>&lt;Test/&gt;</Initial>
      <Set path="Test/#text" value="text content"/>
    </Path>

Editing files outside the default load path
===========================================

If you're using Augeas to edit files outside of its default load path,
you must manually specify the lens.  For instance:

.. code-block:: xml

    <Path type="augeas" name="/opt/jenkins/home/config.xml" lens="Xml"
          owner="jenkins" group="jenkins" mode="0640">
      <Set path="hudson/systemMessage/#text"
           value="This is a Jenkins server."/>
    </Path>

Note that there's no need to manually modify the load path by setting
``/augeas/load/<lens>/incl``, nor do you have to call ``load``
explicitly.

Schema
======

.. xml:group:: augeasCommands


Performance
===========

The Augeas tool is quite slow to initialize.  For each ``<Path
type="augeas" ... >`` entry you have, it creates a new Augeas object
internally, which can take several seconds.  It's thus important to
use this tool sparingly.