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Clarify grains precedence

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Resolves #8107.
This commit is contained in:
Erik Johnson 2013-11-03 13:31:01 -06:00
parent 5ea0ca12b1
commit 3e7f48dd2c
1 changed files with 23 additions and 10 deletions
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33
doc/topics/targeting/grains.rst
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@ -102,15 +102,9 @@ same way as in the above example, only without a top-level ``grains:`` key:
cabinet: 13
cab_u: 14-15
.. admonition:: Precedece of Custom Static Grains
Be careful when defining grains both in ``/etc/salt/grains`` and within the
minion config file. If a grain is defined in both places, the value in the
minion config file takes precedence, and will always be used over its
counterpart in ``/etc/salt/grains``.
Grains in Top file
==================
Matching Grains in the Top File
===============================
With correctly setup grains on the Minion, the Top file used in Pillar or during Highstate can be made really efficient. Like for example, you could do:
@ -168,8 +162,27 @@ grains need to be static data. If the data is something that is likely to
change, consider using :doc:`Pillar <../pillar/index>` instead.
Precedence
==========
Core grains can be overriden by custom grains. As there are several ways of
defining custom grains, there is an order of precedence which should be kept in
mind when defining them. The order of evaluation is as follows:
1. Core grains.
2. Custom grains in ``/etc/salt/grains``.
3. Custom grains in ``/etc/salt/minion``.
4. Custom grain modules in ``_grains`` directory, synced to minions.
Each successive evaluation overrides the previous ones, so any grains defined
in ``/etc/salt/grains`` that have the same name as a core grain will override
that core grain. Similarly, ``/etc/salt/minion`` overrides both core grains and
grains set in ``/etc/salt/grains``, and custom grain modules will override
*any* grains of the same name.
Examples of Grains
------------------
==================
The core module in the grains package is where the main grains are loaded by
the Salt minion and provides the principal example of how to write grains:
@ -178,7 +191,7 @@ the Salt minion and provides the principal example of how to write grains:
Syncing Grains
--------------
==============
Syncing grains can be done a number of ways, they are automatically synced when
:mod:`state.highstate <salt.modules.state.highstate>` is called, or (as noted