NAME

       md_doc_help_elektra-namespaces - elektra-namespaces(7) -- namespaces Every key in Elektra
       has a unique name. Sometimes, multiple keys denote the same configuration item from
       different sources, e.g.:

       • by a commandline argument

       • by a configuration file found below the home directory

       • by a configuration file found below /etc

       To allow such keys to exist in parallel, Elektra uses namespaces.

       A namespace has following properties:

       • in-memory Keys can start with this name

       • these keys stem from a specific configuration source

       • ksLookup() uses namespaces in a specific default order unless specified otherwise

       Following parts of Elektra are affected by namespaces:

       • the key name validation in keySetName()

       • keyGetNamespace() which enumerates all namespaces

       • _Backend and split.c for correct distribution to plugins (note that not all namespaces
         actually are distributed to configuration files)

       • mount.c for cascading and root backends

       • and of course many unit tests

       In the rest of this document all currently available namespaces in the default order are
       described.

   spec
       Unlike the other namespaces, the specification namespace does not contain values of the
       keys, but instead meta data as described in [METADATA.ini].

       When a key is looked up, keys from the spec-namespace are the first to be searched. When a
       spec-key is found, the rest of the lookup will be done as specified, probably in a
       different order than the namespaces enlisted here.

       Usually, the spec-keys do not directly contribute to the value, with one notable
       exception: the default value (meta data default, see in cascading below) might be used if
       every other way as specified in the spec-key failed.

       Spec-keys typically include a explanation and description for the key itself (but not
       comments which are specific for individual keys).

       The spec configuration files are below CMAKE_INSTALL_PREFIX/KDB_DB_SPEC.

       spec is not part of cascading mounts, because the specifications often are written in
       different syntax than the configuration files.

   proc
       Derived from the process (e.g. by parsing /proc/self or by arguments passed from the main
       method):

       • program name

       • arguments

       • environment

       Keys in the namespace proc can not be stored by their nature. They might be different for
       every invocation of an application.

   dir
       Keys from the namespace dir are derived from a directory special to the user
       starting/using the application, e.g.:

       • the current working directory for project specific settings, e.g. .git

       • the directory a server wants to present to the user, e.g. .htaccess

       Note that Elektra only supports a single special directory per KDB instance. Start a new
       KDB instance if you need different special directories for different parts of your
       application. How to change the directory may be different dependent on the resolver, e.g.
       by using chdir or by setting the environment variable PWD

   user
       On multi-user operating systems obviously every user wants her/his own configuration. The
       user configuration is located in the users home directory typically below the folder
       KDB_DB_USER. Other pathes below the home directory are possible too (absolute path for
       resolver).

       Note that Elektra only supports a user directory per KDB instance. Start a new KDB
       instance if you need different user configuration for different parts of your application.
       How to change the user may be different dependent on the resolver, e.g. by seteuid() or by
       environment variables like HOME, USER

   system
       The system configuration is the same for every chroot.

       The configuration is typically located below KDB_DB_SYSTEM. Other absolut pathes, e.g.
       below /opt or /usr/local/etc are possible too.

   cascading
       Keys that are not in a namespace (i.e. start with an /) are called cascading keys.
       Cascading keys do not stem from a configuration source, but are used by applications to
       lookup a key in different namespaces. So, multiple keys can contribute to each cascading
       key name.

       Cascading is the same as a name resolution and provides a namespace unification as
       described in Versatility and Unix semantics in namespace unification.

       Keys without a namespace can not be stored by their nature. So they are transient: after a
       restart they are forgotten.

       Keys of that namespace are only used by ksLookup when no other suitable key was found. So
       they have the lowest possible priority, even fallback keys are preferred.

       Read more about cascading.