.. -*- mode: rst -*- .. _server-plugins-generators-tgenshi-index: ======= TGenshi ======= .. warning:: The TGenshi plugin is deprecated. You should instead use :ref:`server-plugins-generators-cfg-genshi` in the Cfg plugin. 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 `_ 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, 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 `_ 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 ` * **metadata.Properties** is an xml document of unstructured data (only available when used in conjunction with the :ref:`server-plugins-connectors-properties` plugin) * **name** is the path name specified in bcfg * **path** is the path to the TGenshi template. It starts with a leading slash, and is relative to the Bcfg2 specification root. E.g., ``/Cfg/etc/foo.conf/foo.conf.genshi`` or ``/TGenshi/etc/foo.conf/template.newtxt.H_foo.example.com`` See the genshi `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 client is ypbound workstation client is a desktop, but not an ubuntu desktop This flexibility provides the ability to build much more compact and succinct definitions of configuration contents than Cfg can. Troubleshooting =============== When developing a template, you can see what the template would generate on a client with :ref:`bcfg2-info `:: bcfg2-info buildfile E.g.:: bcfg2-info buildfile /etc/foo.conf foo.example.com To generate a file with an altsrc attribute, you can run:: bcfg2-info buildfile /etc/foo/foo.conf --altsrc=/etc/foo.conf \ foo.example.com Sometimes, it's useful to be able to do more in-depth troubleshooting by running the template manually. To do this, run ``bcfg2-info debug``, and, once in the Python interpreter, run:: metadata = self.build_metadata("") path = "" ``path`` should be set to the path to the template file with a leading slash, relative to the Bcfg2 specification root. See `Inside of Templates`_ for examples. Then, run:: import os, Bcfg2.Options from genshi.template import TemplateLoader, NewTextTemplate name = os.path.dirname(path[path.find('/', 1):]) setup = Bcfg2.Options.OptionParser({'repo': Bcfg2.Options.SERVER_REPOSITORY}) setup.parse('--') template = TemplateLoader().load(setup['repo'] + path, cls=NewTextTemplate) print template.generate(metadata=metadata, path=path, name=name).render() This gives you more fine-grained control over how your template is rendered. You can also use this approach to render templates that depend on :ref:`altsrc ` tags by setting ``path`` to the path to the template, and setting ``name`` to the path to the file to be generated, e.g.:: metadata = self.build_metadata("foo.example.com") path = "/Cfg/etc/sysconfig/network-scripts/ifcfg-template/ifcfg-template.genshi" name = "/etc/sysconfig/network-scripts/ifcfg-bond0" 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 arise 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 `_ and `#283: Allow for redefinition of template syntax per-file `_. Examples ======== .. toctree:: :glob: :maxdepth: 1 examples/genshi/*