Rushing the available light

Every so often I need to convert an entire system of some kind to another kind. For example, Debian to Ubuntu, or Ubuntu to Debian, or i386 to amd64. Prior to the existence of either Ubuntu or amd64, this type of thing was much, much easier. The main problems are that apt and dpkg trust the contents of /var/lib/dpkg/available, and so do the postinst scripts and whatnot.

So as we get more and more sources of .deb files and as postinst files make more and more assumptions based on the version passed as previously installed, opportunities for error increase, whether or not you're editing the available file to facilitate some sort of conversion.

I've been complaining about this sort of thing since the dawn of time, but everyone always says, « That's not supported, so fuck off. » This is it will be difficult if not impossible to install simultaneously multiple MTA packages for the foreseeable future.

So if the udev package preinst checks the previous version to determine whether or not to perform certain actions, and you happen to have a udev package created by someone other than the Debian maintainer, you may find yourself facing completely unexpected behavior because this other package did not meet the expectations of the Debian package.

Of course, the udev package can't possibly attempt to know about all the other potential udev packages that anyone might build.

There's no telling whom the angry owl will attack.