bionic (3) md_src_plugins_augeas_README.3elektra.gz

NAME

       md_src_plugins_augeas_READMEREADME
        -

       • infos = Information about augeas plugin is in keys below

       • infos/author = Felix Berlakovich elektra@berlakovich.net

       • infos/licence = BSD

       • infos/needs =

       • infos/provides = storage

       • infos/recommends = glob keytometa

       • infos/placements = getstorage setstorage

       • infos/description = reading and writing configurations via libaugeas

       This is a plugin for reading and writing configuration files with help from Augeas. The plugin should be
       able to read all configuration files for which an Augeas lens exists. However, not all stock lenses of
       Augeas have been tested yet. A detailed description of the lens language and a tutorial on how to write
       new lenses" can be found at http://augeas.net/

   DEPENDENCIES
       • libaugeas-dev #note: You need version 0.16 or higher which is not in debian wheezy

   INSTALLATION
       If you have installed Augeas manually, it may be neccessary to update the ld configuration. This is
       especially true if an older version of Augeas is installed also. Such a situation may lead to an error
       similar to this:

       /usr/lib/libaugeas.so.0: version `AUGEAS_0.16.0' not found (required by kdb)

       This is because ld tries to link /usr/lib/libaugeas.so.0 which is an older version of Augeas. Simply add
       the path to the newer library to your ld search paths (consult your system documentation on how to do
       this)

   MOUNTING AND CONFIGURATION
       In order to mount the hosts file with the augeas plugin, issue the following command:

           kdb mount /etc/hosts system/hosts augeas lens=Hosts.lns

       The value of the plugin configuration option 'lens' should be the module name of the lens (Hosts in the
       example) with a '.lns' suffix. Depending on your distribution and kind of installation, lenses can be
       found at /usr/share/augeas/lenses/dist, /usr/local/share/augeas/lenses/dist, or something similar. The
       lens module name is equal to the filename without extension in pascal notation. For example, the lens
       /usr/share/augeas/lenses/dist/hosts.aug contains the module Hosts.

       Note that, without configuring the plugin to use a lens, the plugin would bail out an error on the first
       usage:

           kdb ls system/hosts
           The command ls terminated unsuccessfully with the info: Error (#85) occurred!
           Description: an Augeas error occurred
           Ingroup: plugin
           Module: storage
           At: /path/augeas.c:166
           Reason: Lens not found

       because the plugin would not know which lens to use to read and write the configuration. For that reason,
       the lens configuration option was supplied together with the mount command.

   RESTRICTIONS
   Inner node values
       Currently no Augeas lens supports values for inner nodes. Unfortunately no validation plugin exists yet
       that would prevent such modifications early:

           kdb set system/hosts/1 somevalue
           The command set terminated unsuccessfully with the info: Error (#85) occurred!
           Description: an Augeas error occurred
           Ingroup: plugin
           Module: storage
           At: /path/augeas.c:166
           Reason: Malformed child node '1'

       The operation simply fails with an undescriptive error.

   Leaky abstraction of order
       Most Augeas lenses require subtrees to be in a specific order. For example the hosts lens requires the
       ipaddr node of an entry to precede the canonical node. Unfortunately the Augeas storage plugin has no
       knowledge about this required order. Therefore the correct order must be ensured via order meta keys.
       Otherwise saving the KeySet may fail. As an example consider the following kdb shell script:

           kdbGet system/hosts
           keySetName system/hosts/6
           ksAppendKey
           keySetName system/hosts/6/ipaddr
           keySetString 14.14.14.14
           ksAppendKey
           keySetName system/hosts/6/canonical
           keySetString newhost
           ksAppendKey
           kdbSet system/hosts

       This fails with an error similar to this

           Description: an Augeas error occurred
           Ingroup: plugin
           Module: storage
           At: /path/augeas.c:179
           Reason: Failed to match
           some augeas match expression
           with tree
           {

       Wheras the following script succeeds due to the correct order

           kdbGet system/hosts
           keySetName system/hosts/6
           ksAppendKey
           keySetName system/hosts/6/ipaddr
           keySetString 14.14.14.14
           keySetMeta order 100
           ksAppendKey
           keySetName system/hosts/6/canonical
           keySetString newhost
           keySetMeta order 110
           ksAppendKey
           kdbSet system/hosts

   PLANNED IMPROVEMENTS
       • a validation plugin preventing inner node values,