Monday, 27 September 2010

Configuration files: an important assumption debian takes

It took me more than expected (and in fact someone found it for me) to explain why a file installed by a debian package and not listed inside debian/conffiles was handled as a standard configuration file.

The file is installed in a subdirectory of /etc/, so intuitively you may assume it must be considered as a configuration file, although this wasn't clearly stated in a document until I read this from Debian New Maintainer's Guide , chapter 5:

Since debhelper V3, dh_installdeb(1) will automatically flag any files under the /etc directory as conffiles, so if your program only has conffiles there you do not need to specify them in this file. For most package types, the only place there is (and should be conffiles) is under /etc and so this file doesn't need to exist.

The conclusion is that if you install a file in a subfolder of /etc/, you don't need to list it inside debian/conffiles.


Saturday, 25 September 2010

Order of Ignorance

This is a concept that I've always found interesting.

This evening I recalled it and found a blog article with other classifications of order of ignorance.

This is the version I already knew:

0OI: I have Zeroth Order Ignorance (0OI) when I know something and can demonstrate my lack of ignorance in some tangible form, such as by building a system that satisfies the user.

1OI: Lack of Knowledge. I have First Order Ignorance (1OI) when I don’t know something and I can readily identify that fact.

2OI: Lack of Awareness. I have Second Order Ignorance (2OI) when I don’t know that I don’t know something. That is to say, not only am I ignorant of something (I have 1OI), I am unaware of that fact.

3OI: Lack of Process. I have Third Order Ignorance (3OI) when I don’t know of a suitably efficient way to find out that I don’t know that I don’t know something. So I am unable to resolve my 2OI.


In my words:
Level 0: I know the problem and I can solve it because I've already done it before.
Level 1: I know the problem but I don't know how to solve it.
Level 2: I don't know I have a problem.
Level 3: I don't know how to identify if I have a problem.


Variation is where assigned cause has been eliminated and only chance cause exists within a known and understood system.

Foreseen Uncertainty is where there are identifiable risks and understood issues which affect the delivery of the project but the basic market for the deliverable is understood and the business model or go-to-market strategy is understood. However, there is sufficient uncertainty that assignable cause variation will be observed and must be dealt with through aggressive issue log management.

Unforeseen Uncertainty will feel out of control most of the time and what gets delivered won't be exactly what the customer wanted or when they wanted it. This could be because the software development is happening with a new paradigm of tools or method - when teams start using MDA or DSLs for example - but it may also occur in new markets where the business model is not understood and the degree of variation cannot be predicted. The answer is to iterate frequently and plan adaptively. It is primarily this class of project which Doug DeCarlo addresses with his Extreme Project Management method.

Finally, there is Chaos, the land where we don't know what we don't know and we are trying to find out - neither the market, the business model, the customer base, the product features, or the technology are understood. It's the land of research projects.

In my words:
Variation: No uncertainty. You know the market and what to push on it.
Foreseen uncertainty: You know what problems can arise and you're ready to face them.
Unforseen uncertainty: What you deliver is different than what you've planned because uncertainties moved your scope.
Chaos: You don't know what to do and how to do it.

If I could decide, I'd choose to work in a scenario where I have Order of Ignorance 1 (I know the problem but I need to learn how to solve it) and Forseen Uncertainty, as I find it the most interesting to be in.

I know what your question might be at this point: "It's Staurday night and the most exciting thing you can do is... write this post?".
Well, you can classify your plans for a Saturday night in 4 different categories...