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.. -*- mode: rst -*-
.. _server-plugins-generators-tgenshi-index:
=======
TGenshi
=======
This page documents the TGenshi plugin. This plugin works with version
0.4 and newer of the genshi library.
The TGenshi plugin allows you to use the `Genshi
<http://genshi.edgewall.org>`_ templating system to create files,
instead of the various diff-based methods offered by the Cfg
plugin. It also allows you to include the results of probes executed
on the client in the created files.
To begin, you will need to download and install the Genshi templating engine.
To install on CentOS or RHEL 5, run::
sudo yum install python-genshi
Once it is installed, you can enable it by adding ``TGenshi`` to the
generators line in ``/etc/bcfg2.conf`` on your Bcfg server. For example::
plugins = Base,Bundler,Cfg,...,TGenshi
The TGenshi plugin makes use of a Cfg-like directory structure
located in in a TGenshi subdirectory of your repository, usually
``/var/lib/bcfg2/TGenshi``. Each file has a directory containing two file
types, template and info. Templates are named according to the genshi
format used; template.txt uses the genshi text format, and template.xml
uses the XML format.
If used with Genshi 0.5 or later the plugin also supports the `new
style
<http://genshi.edgewall.org/wiki/Documentation/0.5.x/text-templates.html>`_
text template format for files named template.newtxt. One of the
advantages of the new format is that it does not use # as a command
delimiter, making it easier to utilize for configuration files that
use # as a comment character.
Only one template format may be used per file served. Info files are
identical to those used in ``Cfg``, and ``info.xml`` files are
supported.
Inside of templates
===================
* **metadata** is the client's :ref:`metadata <server-plugins-grouping-metadata-clientmetadata>`
* **properties.properties** is an xml document of unstructured data
* **name** is the path name specified in bcfg
* **path** is the path to the TGenshi template
See the genshi `documentation
<http://genshi.edgewall.org/wiki/Documentation>`_ for examples of
Genshi syntax.
Examples: Old Genshi Syntax
---------------------------
Genshi's web pages recommend against using this syntax, as it may
disappear from future releases.
Group Negation
^^^^^^^^^^^^^^
Templates are also useful for cases where more sophisticated boolean
operations than those supported by Cfg are needed. For example, the
template::
#if "ypbound" in metadata.groups and "workstation" in metadata.groups
client is ypbound workstation
#end
#if "ubuntu" not in metadata.groups and "desktop" in metadata.groups
client is a desktop, but not an ubuntu desktop
#end
Produces:
.. code-block:: xml
<Path type="file" name="/bar.conf" owner="root" perms="0644" group="root">client is ypbound workstation
client is a desktop, but not an ubuntu desktop
</Path>
This flexibility provides the ability to build much more compact and
succinct definitions of configuration contents than Cfg can.
File permissions
================
File permissions for entries handled by TGenshi are controlled via the
use of :ref:`server-info` files. Note that you **cannot** use both a
Permissions entry and a Path entry to handle the same file.
Error handling
================
Situations may arrise where a templated file cannot be generated due to
missing or incomplete information. A TemplateError can be raised to
force a bind failure and prevent sending an incomplete file to the client.
For example, this template::
{% python
from genshi.template import TemplateError
grp = None
for g in metadata.groups:
if g.startswith('ganglia-gmond-'):
grp = g
break
else:
raise TemplateError, "Missing group"
%}\
will fail to bind if the client is not a member of a group starting with
"ganglia-gmond-". The syslogs on the server will contain this message::
bcfg2-server[5957]: Genshi template error: Missing group
bcfg2-server[5957]: Failed to bind entry: Path /etc/ganglia/gmond.conf
indicating the bind failure and message raised with the TemplateError.
FAQs
====
**Question**
How do I escape the $ (dollar sign) in a TGenshi text template? For
example, if I want to include SVN (subversion) keywords like $Id$ or
$HeadURL$ in TGenshi-generated files, or am templating a bourne shell
(sh/bash) script or Makefile (make).
**Answer**
Use $$ (double dollar sign) to output a literal $ (dollarsign)
in a TGenshi text template. So instead of $Id$, you'd use
$$Id$$. See also Genshi tickets `#282: Document $$ escape
convention <http://genshi.edgewall.org/ticket/282>`_ and
`#283: Allow for redefinition of template syntax per-file
<http://genshi.edgewall.org/ticket/283>`_.
Examples
========
.. toctree::
:maxdepth: 1
bcfg2-cron
clientsxml
ganglia
grubconf
hosts
iptables
motd
mycnf
test
|
