There are a fair number of open source Unixes around and over time I've wound up with some jaundiced perceptions of what their various ecological niches are. Today I feel like writing them up, with the disclaimer that this is not just in my own view but that it is my view of what perceptions of these Unixes are, not necessarily the reality.

Linux

Everyone knows this one. Linux's niche is as the popular and widely used open source Unix, and as a result it's the one that almost everyone makes sure their programs run on and writes software to. On its primary hardware platforms, Linux's hardware support is basically unmatched; if there's a driver for something, Linux was probably the first target. Linux is what you use by default or if you don't want to take any risks.

(For example, notice that mozilla.org provides Firefox builds for Linux but not for other open source Unixes.)

FreeBSD

FreeBSD's niche is being the non-Linux. It's what you run if you want a well done free Unix that is not Linux. It doesn't get the love (and the software) that Linux does, but it's popular enough to mostly keep up in most settings. The developers of open source programs (at least ones that aren't intended to be Linux specific) will probably not laugh at you if you report 'fails to work properly on FreeBSD' bugs to them.

OpenBSD

OpenBSD has determinedly created a niche as the firewall and networking Unix and as what you run if you care much more about (remote) security than anything else. Note that this is not quite the same as 'the secure one'. Because of its focus on security and the accompanying minimalism OpenBSD is generally behind the times in terms of features, software versions, and so on (the abrasive personalities involved don't help either). The developers of most open source programs may just look at you bemusedly if you report 'fails to work properly on OpenBSD' bugs.

NetBSD

To the extent that this has an ecological niche, it's running on CPU architectures and hardware platforms that are too obscure or old for Linux (or anything else). The motto on their website really summarizes it well: "Of course it runs NetBSD". The flipside of this is that NetBSD is not something you run if you have a choice.

The remaining open source Unixes are either effectively in very specialized niches (regardless of what they wish to be seen as), lack clear niches where they are the leading choice, or both. For example, DragonFlyBSD would probably like to be in FreeBSD's ecological niche but is too obscure.

(You may also want to see my entry on where the Unix community wound up.)