update-conf.d script for flexible /etc/<conf>.d configuration

Origin

In January 2008 I wrote a very simple shell script to manage fstab entries in the way like environment variables in /etc/env.d are managed. For this I created separated fstab files in /etc/fstab.d and wrote a shell script called update-fstab.

I then released it in 2010 on the Gentoo Forum in the hope that it would be useful to anyone.

Since then a few people have made enhancements, and the shell script is now even able to handle any <conf>.d directory in the same way. It is now called update-conf.d.

In October 2011 I created this Git repository. If you want to contribute: every improvement, fix, patch is welcome!

2012-01-05, Atha

Debian 6/7 libmount

WARNING

"update-conf.d fstab" is incompatible with Debian bug #663623 which adds /etc/fstab.d support in libmount, part of util-linux. Adding support to the mount command was discussed by certain developers on the LKML, but not yet implemented. On a Debian 6 "Squeeze" and 7 "Wheezy" system /etc/fstab.d already exists and is probably used by libmount. Hence, be very very careful when you use update-conf.d with /etc/fstab on a Debian 6/7 based distribution!

In Debian 8 "Jessie" (2015) this libmount behaviour was removed.

Installation

There are two versions: simple and complex.

First, clean previously built versions:

make clean

Then, to build the complex version:

make complex
make install

The simple version may be preferred when size and speed is a concern. It has less options, but is much simpler, allowing easier modification to the shell script itself, should it be needed.

To build the simple version:

make simple
make install

It basically does the same as the complex version, so the usage should be almost exactly the same.

You will then have to manage /etc/update-conf.d.conf right after the installation, or update-conf.d will have no function. Read the man page for further details.

To uninstall, run make again.

make uninstall

This will remove /usr/local/sbin/update-conf.d.

You can set the PREFIX variable in the Makefile if you want to install it into anything other than /.

Gentoo Linux

It's very easy to install update-conf.d on Gentoo Linux. The following example assumes /usr/local/portage as your local portage directory (see Gentoo Wiki pages Ebuild repository and /etc/portage/repos.conf for more information):

mkdir -p /usr/local/portage/app-admin/update-confd
wget -O /usr/local/portage/app-admin/update-confd/update-confd-9999.ebuild https://raw.githubusercontent.com/Atha/update-conf.d/master/update-confd-9999.ebuild

The update-conf.d script will then be available for installation via portage:

emerge -a app-admin/update-confd

Usage

Please read the man page for options included in the complex version. The following will work also for the simple version:

<conf> is any configuration file you like to make .d'ed, i.e. split into snippets. When reading this, simply substitute <conf> by the name of the configuration file you want to process. Examples: fstab, hosts

• Copy existing configuration

  Copy it to a (newly created) .d'ed directory:

    cd /etc
    mkdir <conf>.d
    cp <conf> <conf>.d/00original
  

  Example: If your <conf> is fstab, you will now have /etc/fstab.d/00original

• Add .d'ed directory to /etc/update-conf.d.conf

    echo <conf> >> /etc/update-conf.d.conf
  

  You may use your favorite text editor to add/delete entries and manage /etc/update-conf.d.conf.

• Test

  This will take all files in /etc/<conf>.d/ that start with two digits (^[0-9][0-9]), leave out empty lines and comments ^[#] and make a new /etc/<conf> with this information.

    update-conf.d <conf>
  

  Example:

    update-conf.d fstab
  

• Configure snippets

  Now take your existing 00original apart and split it up into snippets that suit your needs. If you need examples for snippets and filenames, look at your /etc/env.d directory. The original configuration file 00original can then be deleted or renamed, like A0original or .00original or even <conf>-backup, so it won't be included by the update-conf.d script. Now re-run update-conf.d <conf> to update /etc/<conf>.

Concept

1. Why would you want to split a configuration file into snippets?
   • For one, you may like a modular configuration basis. You can have individually columned configuration files that would normally only make your single (original) configuration file harder to read.
     Take fstab for example. Lines for proc, sysfs, tmpfs, swap will have different column sizes than UUID based partitions or partitions assigned by path in /dev/disk/by-path/, which require different columns than partitions assigned like /dev/sda1. Now you can have seperate files for that, each with an individual # comment line for the columns, making each file very easy to read and edit.
   • You can use different sources for each snippet. For example, you could share a snippet over the network, to have multiple installations updated at the same time. All you have to do is make sure the update-conf.d script is run after syncronizing it, and you're done.
2. What other positive effects can I expect?
   • Your /etc/<conf> is now reproducable by running the update-conf.d script. Accidentally deleting it or altering its contents doesn't destroy your whole configuration.
   • You can experiment with <conf> by changing it, which will only be temporary until you re-run update-conf.d.
   • You can easily disable a snippet by renaming it to not start with two digets. The shell script will then ignore it and thus it will not be included in /etc/<conf> when you run update-conf.d.
   • Applications or self written scripts cannot harm your <conf> file by destroying it (accidentally).
3. Are there any negative effects?
   • Yes.
   • If you rely on applications to update your /etc/<conf>, you must manually add this update to your /etc/<conf>.d/00something snippet. Otherwise it will be lost the next time you run update-conf.d. Some Linux distributions update /etc/fstab and /etc/hosts (and possibly others) when the system configuration is changed.
   • On some systems, other utilities may already use a .d'ed directory in /etc, which makes it impossible to use update-conf.d without a PREFIX. One example is Debian's libmount (since around 2011, until 2015) which uses /etc/fstab.d. As a sane precaution you should not create a .d-ed directory for this shell script when there already is one!

Versioning

No version numbers are used, instead the date in the ISO format (2008-01-20) is used as the version identification.

The original script update-fstab is depricated and only included for completeness and historical nostalgia. Don't use it.

Adaptation

If you require such a shell script for a very specific task, you may want to modify it to what is needed for this very task. For that you may find the simple version of the update-conf.d script or even the depricated update-fstab script more convenient, since both are certainly simpler and easier to adapt than the complex version. If you do consider modification to the complex version, be advised that the main function is update_confd ().

Contribution

Please, feel free to point out any error. Improvements, fixes and patched are highly appreciated!

Copyright and license

Copyright © 2015 Mic92 (fixes)
Copyright © 2013 javeree
Copyright © 2011 Nicolas Bercher
Copyright © 2010 truc (on improvements)
Copyright © 2008-2023 Atha

This shell script is released under the terms of the GNU GENERAL PUBLIC LICENSE Version 2 or (at your option) any later version. It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY.