bionic (7) elektra-related.7.gz
NAME
elektra-related - related configuration systems
Settings and preferences are ubiquitous in every software. For this reason, a vast amount of software has
emerged on this topic. Most of the other projects, however, do not devote their work exclusively to
configuration.
Configuration Libraries
We have already mentioned that Elektra provides the features of a configuration library. There are
countless libraries out there that parse and some even generate configuration files. But there is a big
catch: These libraries do not provide an abstract view of configuration. They require programmers to open
the files themselves or at least to remember the path to them. Such information is itself configuration
and inherently operating system dependent. Therefore, it is not possible to give default values that just
work.
Another feature mostly missing in these libraries is cascading. It is not difficult to implement, but
disturbing if it is not available at all or does not work correctly.
Augeas
Augeas is not intended for applications themselves, so it only creates a new view to configuration files
which is not necessarily the same as applications see it. Additionally, Augeas has a rather poor level of
abstraction and many syntactical details must be reflected in the configuration tree. Nevertheless,
Elektra provides an /src/plugins/augeas/ augeas%20plugin which allows parts of Elektra´s global
configuration tree to be implemented using lenses. Lenses are a promising technology, which allow mapping
from and to configuration files to be specified with a single program.
Uniconf
A project that shares some of the goals with Elektra, but uses a different approach is Uniconf. Besides a
stand-alone library it supports a daemon mode. With the daemon running, it has the disadvantage of
protocol overhead and a single point of failure. On the other hand, Uniconf can also notify applications
when configuration files change and can work in a distributed mode. The project does not solve the
problem of how to configure the configuration system. So we still have to pass a so-called moniker string
that contains the knowledge where to find the configuration. The plugin system is flexible, but does not
depend on the key name. So it is not possible to use different plugins for different applications and
still have a global key database.
Debconf
Debconf is a set of Debian-tools that separates user interaction from the configuration process for the
system´s configuration when packages are installed or upgraded. Debconf itself does not change the
configuration files. Instead, the administrator is asked questions depending on template files using
different front ends. These answers are then cached. The configuration changes themselves are applied by
post-install scripts of the particular package. Exactly for this last step Elektra could yield much
better results, because it can compare configuration on a per-key basis and thus handle conflicts in a
much more fine-grained way.
Freedesktop.org
The freedesktop.org initiative unifies different desktops using the X Window System in various ways. The
main focus, however, lies in KDE and Gnome integration. One of the most disturbing and still unresolved
problems is configuration. Elektra intends to fill this gap in the future.
Already available is the so-called XDG Base Directory Specification. Perhaps it will define file formats
in the future, but currently only the paths are specified. To do so, it introduces some environment
variables that help to find the actual configuration. Only if they are unset or empty, a built-in
fallback should be used. If desired, elektrified applications behave in a XDG conforming way. (See the
configuration x for the resolver /src/plugins/resolver/).
July 2017 ELEKTRA-RELATED()