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Improve documentation for image creation

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Add the tree-like vs complete digraph configuration
for images. This is a partial refactor from
I3600c6a3d663c697b59d91bd3fbb5e408af345e4

Change-Id: Ia7a8321e63d59771fe47d8e262b9aacffd60d8d9
Co-Authored-By: Andreas Florath <andreas@florath.net>
This commit is contained in:
Yolanda Robla 2017-05-01 12:19:26 +02:00 committed by yolanda.robla
parent 629b81bc9b
commit 340451ea00
1 changed files with 49 additions and 0 deletions
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doc/source/user_guide/building_an_image.rst
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@ -86,6 +86,55 @@ The default is:
In general each module that depends on another module has a `base`
element that points to the depending base.
Tree-Like vs. Complete Digraph Configuration
++++++++++++++++++++++++++++++++++++++++++++
The configuration is specified as a digraph_. Each module is a
node; a edge is the relation of the current element to its `base`.
Because the general digraph_ approach is somewhat complex when it comes
to write it down, the configuration can also be given as a tree_.
.. _digraph: https://en.wikipedia.org/wiki/Directed_graph
.. _tree: https://en.wikipedia.org/wiki/Tree_(graph_theory)
Example: The tree like notation
.. code-block:: yaml
mkfs:
name: root_fs
base: root_part
mount:
mount_point: /
is exactly the same as writing
.. code-block:: yaml
mkfs:
name: root_fs
base: root_part
mount:
name: mount_root_fs
base: root_fs
mount_point: /
Non existing `name` and `base` entries in the tree notation are
automatically generated: the `name` is the name of the base module
prepended by the type-name of the module itself; the `base` element is
automatically set to the parent node in the tree.
In mostly all cases the much simpler tree notation can be used.
Nevertheless there are some use cases when the more general digraph
notation is needed. Example: when there is the need to combine two or
more modules into one new, like combining a couple of physical volumes
into one volume group.
Tree and digraph notations can be mixed as needed in a configuration.
Limitations
+++++++++++
The appropriate functionality to use multiple partitions and even LVMs