Configuration Files

Just a short story as a starter:

I went to a Covid19 test and a colleague asked the very legitimate question, why I am doing a test in spite of being vaccinated twice.

This has a lot to do with configuration of software.

There are configuration files, that are the rules that local, regional, national or EU government impose. They typically prepare rules, publish them and activate them on a given date, but sometimes they become active immediately. The first case is a like using a more or less clean process for managing configurations and the second case is like adhoc editing with vi. Both have their place, but the second case should be understood as a rare exception that is needed to keep the system running and there should be steps to follow afterwards to document this change and to feed it into the process afterwards.

So the rules by governents confingure for example border controls and controls at airports. At each border and at each airport or port there are natural checkpoints where a person can be stopped. When travelling by train, by bicycle, by car or by motorcycle, there are usually only the border controls.

Now these configurations change freqently and there are a lot of complex rules. Like configuration files of software in real life.

So it can happen, that somewhere they ask for a test even if the person has benn vaccinated. Or in other situations the vaccination is enough. Or the proof of vaccination has to be given in a certain format, that is maybe still impossible to get. Or the vaccination only counts if it has been done using a certain vaccine. Now it is advisable to equip oneself in such a way that it is possible to pass absolutely all checkpoints of the whole trip.

Now there can be errors in the system. For example the persons who run a checkpoint might not know the rules valid at that particular day correctly and stop someone who actually complies with the rules.

It is said that it has been known 2000 years ago that the configuration of customs control have been falsified in an ad hoc manner. Not only by mistake, but actually voluntarily.

I think that this describes quite well the challenges and complexities of managing software configuration.

So almost every software has some configuration that comes with it.

This can be flat files, that are more or less specific to configuration.

It can be stored in a database. This can be a classical SQL database or a NoSQL-database or some kind of lightweight database that is accessed only via a library.

Configuration can be prepared in advance.

Or it is edited on the server.

Or it is edited using settings of the software via its GUI.

Now for a seriously managed software installation, it is a good idea to have well defined installation artifacts, which includes the configuration. But less technical configuration can actually be changed by sophisticated end users and this can be actually the right way to do it.

It is a good idea to keep some understanding of the configuration of the software. A way to do this is to have it in git, possibly using tags and or branches. I do not recommend to actually have git on all the machines directly, but rather to have some configuration master server on which the files are edited, prepared and pushed into git. Then they can be pushed to the servers by some mechanism, via tools like ansible or via simple scripts…

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