DynConf

DynConf is a small program to apply recipes to configuration files. This can be used to dynamically alter a configuration without diverging from the defaults: When there is an update you simply re-run DynConf to produce a new configuration file. In this case the recipes describe which lines should be deleted, replaced, or appended.

The executable expects one of the following subcommands:

• apply takes a recipe, produces a configuration file and writes the result. (You might need to run this subcommand as root to modify files in /etc/.)
• check validates the given recipe.
• show produces a configuration file, but outputs the result for inspection.

Recipes are written in YAML and look like this:

file: "/etc/test.conf"

delete:
  -
    context:
      begin: "begin"
      end: "end"
    search: "remove"
    checkCount: 1

replace:
  -
    context:
      begin: "begin"
      end: "end"
    search: "pattern"
    replace: "substitution"
    checkCount: 1

append: "last line"

delete and replace are arrays and their search key is interpreted as regular expression.

context is optional and allows to restrict delete and replace to a subset of the file. begin and end are interpreted as regular expressions and matched to input file before deleting a line or replacing its contents. If begin or end is omitted, the context begins in the first line or ends at the last. begin and end do not match the same substring, ie. end can only match from the position where the match of begin ended. However, if begin and end still match at the same line the context will not be enabled.

checkCount is also optional and denotes how often a delete or replace is expected to be applied. If the expectation does not hold, DynConf will print an error and not apply the recipe.

file names the configuration file that should be produced. The unmodified input is taken from (in this order):

1. An updated configuration file installed by the distribution's package manager. For example, on Arch Linux these are called .pacnew, rpm calls them .rmpnew.
2. A saved copy of the unmodified configuration file, suffixed with .orig.
3. If all else fails DynConf will modify the configuration file itself.

To ensure idempotence DynConf will create an unmodified copy and suffix it with .orig. As seen in the previous paragraph, updates have higher priority and an invocation of apply will work with the new configuration file. In addition, DynConf will update the .orig file and remove the new file installed by the package manager.

License

The code is released under the GNU General Public License v3:

Copyright (C) 2018 - 2019  Jonas Hahnfeld

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

Individual files contain the following tag instead of the full license text.

SPDX-License-Identifier:	GPL-3.0-or-later

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