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BSD For Linux Users
noackjr writes "Matt Fuller posted among his rants a great introduction and explanation of BSD For Linux Users: 'It's been my impression that the BSD communit{y,ies}, in general, understand Linux far better than the Linux communit{y,ies} understand BSD. I have a few theories on why that is, but that's not really relevant. I think a lot of Linux people get turned off BSD because they don't really understand how and why it's put together. Thus, this rant; as a BSD person, I want to try to explain how BSD works in a way that Linux people can absorb.'"
Who are the characters?
Meet the players
I'll give here a quick introduction to and discussion of the systems I'll be talking about. Note that the histories presented are not comprehensive or authoritative, and no attempt has been made to make them that way. Deal.
Unix
Unix isn't (precisely) an operating system.
Well, it is, and it isn't.
In specific usage, Unix is an operating system originally developed in the late 60's at Bell Labs by Ken Thompson and Dennis Ritchie. Over the years since then it's been developed and distributed as a commercial operating system, and a research operating system, by Bell Labs and USG and USDL and ATTIS and USL and Novell and SCO and anybody else who could come up with an acronym.
It's probably not too much exaggeration to say that Unix is the single most influential operating system in modern computing. Every general-purpose computing device you'll find, and a lot of specific-purpose computing devices, will be using ideas and concepts and often code from something in the Unix family tree.
When we use the word 'Unix', then, we far more often mean the general form, than the specific OS that carries the name Unix(TM). The general form means "Any operating system which, in design and execution and interface and general taste, is substantially similar to the Unix system." That means all the BSDs, Linuxen, SunOS, Tru64, SCO, Irix, AIX, HP/UX, and a cast of hundreds or thousands of others.
I'm not interested in getting into semantic discussions about how many angels can dance on a head of split hair. Let it suffice that when I use phrases like "Unix systems", I mean exactly what you think of when I use the phrase. Pedantry City is ---> that way.
Linux
Linux also means several things. It's a kernel, originally written by Linus Torvalds when he was a student in Finland. Since then it's been beat up, punched around, tweaked, poked, prodded, manged, digested, spit out, stomped on, chewed up, tossed out, brought in, and otherwise manipulated (not necessarily in that order, of course) by more other people than you could easily count.
Linux is also the term for a family of operating systems. While there are fascinating metaphysical discussions taking place in dozens of places around the world at this very second (I guarantee it) about how "Linux isn't really an operating system, it's just a kernel", or "It should be called 'GNU/Linux'", or similar topics, I'm also going to neatly avoid that semantic cesspool. When I say "Linux", I mean Red Hat. I mean Slackware. I mean Mandrake. I mean Debian. I mean SuSe. I mean Gentoo. I mean every one of the 2 kadzillion distributions out there, based around a Linux kernel with substantially similar userlands, mostly based on GNU tools, that are floating around the ether.
BSD
BSD stands for "Berkeley Software Distribution". Originally, it was a set of patches and extra add-on utilities for the official Bell Unix system that were developed by the CSRG at the University of California, Berkeley. Over time, it evolved to change and/or replace more and more of the system, until at some undefined point it became basically its own OS that merely happened to share chunks of code with Bell's Unix system.
Of course, it still required that you have a Bell license to use the system, since a lot of it was still Bell's code. All of the code written by Berkeley, however, was released under what's come to be known as the BSD license, which basically translates to "Do whatever the hell you want with the code, just give us credit for writing it". And a lot of the BSD code ended up working its way back into the "official" Unix system too, in System III and System V. And, a lot of both strains worked their way into the various commercial forks of Unix.
After the CSRG (mostly) dissolved and stopped developing the BSD system, several groups went off different ways with the code. One of these was the 386BSD project, which took the BSD code and made it run on the Intel i386 platform.
Help Brendan pay off his student loans
The BSDs all keep the system under revision control; all the free BSDs use CVS. Revision control (in extremely brief) is a process by which editing a program means checking out a file or group of files, making the changes, then checking in the new versions, along with a message describing the change. A full history of all changes is kept in the revision control system, so you can view a history of the changes, check out an old version, look at the differences between arbitrary versions, etc.
All the BSDs provide public access to their CVS repositories in one way or another; generally through anonymous CVS, or CVSup checkout or mirroring, or often both. That means that, as a user, you can see exactly what changes happened when, who did them, and why they did them. You can also always get your hands on the latest changes (within a few hours, anyway, depending on mirroring strategies). All of the free BSDs have mailing lists that you can subscribe to and see the changes as they're made. In fact, they all have web frontends as well; you can poke around FreeBSD's entire source tree online at http://cvsweb.freebsd.org/src/, and see all the history of every file.
Linux, historically, hasn't used any version control for the kernel. I don't have exact data at my fingertips here, but I believe it was somewhere in mid-2.4 days that the kernel began being kept in a public BitKeeper repository. Many of the other utilities use revision control, but since they're all developed separately, there isn't any central place you can go to to look through the changes. So it's sometimes hard to get a historic picture of even any one part; to so do for a whole distribution is practically impossible.
This leads to a lot of differences. In a very real sense, BSD systems are constantly developed; I can always update my system to the absolute latest code, irrespective of "releases". In Linux, that doesn't really have as much meaning, because the release process is very different. I think the most appropriate verb for a Linux release is "assembled". A Linux release is assembled from version A.B of this program, plus version C.D of this program, plus version E.F of this program... all together with version X.Y.Z of the Linux kernel. In BSD, however, since the pieces are all developed together, the verb "cut" makes a lot more sense; a release is "cut" at a certain time.
Linux releases kernels in two parallel lines (well, often more than 2, but we're simplifying); a version with an odd minor release number, as a "development" version, and a version with an even minor release number, as a "production" version. The BSDs also have "development" and "production" tracks, but they're handled rather differently.
CVS, like most version control systems, has the concept of "branches". It's easy to understand, but somewhat difficult to explain. Basically, when you "branch" a file or a set of files (or a whole directory tree), you create a new version of the file which exists in parallel with the primary version. When you make changes to the primary version, it doesn't affect the branched version. And you can make changes to the branched version without affecting the primary.
In FreeBSD, there's usually 2 active development lines; one called "-CURRENT", which is the development version, and the other called "-STABLE", which is the production version. Both, of course, are under development, and both have some attempt to be made to keep them usable. -STABLE, as a rule, gets bug and security fixes, but only gets new features and such that are well tested, usually by a stint in -CURRENT first. -CURRENT gets new features, big architectural changes, and all those sorts of new development stuff. It should be noted that the naming of the branches doesn't necessarily mean what it seems to; while -STABLE usually is "stable" as in
The Ports System
Then, there's the second category; those programs which are add-on packages. In the BSD world, this is usually called the "ports system". That name is chosen for a specific reason.
Traditionally, when you wanted to run a package on your system, the first thing you had to do was compile it. And often before you could compile it, you'd have to fiddle with it. Your system would require different header files. Sometimes, manifest constants would be different. Sometimes, you'd even need to rewrite parts of it from scratch, because of basic assumption that didn't hold on your system.
Or, in other words, you'd have to "port" it to your OS, and/or to your specific system. The basic intent of the ports system is to do all that "porting" stuff for you. That it also automates building and installing, and provides packaging services (for things like 'uninstall') isn't as well reflected in the name.
But as with many things, it grew past its name into the beast it is today. The current FreeBSD ports collection has close to 10,000 packages in it (this number will, of course, be outdated quickly, but that's the nature of development). The most obvious feature of ports is that it builds things from source all the time, rather than just install pre-build binaries. This, it seems, is another one of those blatant differences that trip people up when trying to look at BSD from a Linux perspective. That it builds from source is just a side effect, it's not the primary purpose or difference. Binary packages are also available; in fact, binary packages are built from the ports tree!
Now, it's true that most Linux users install binary packages, and most BSD users install by building from source. Partly, that's a result of the tools; the ports system is designed around the concept of building from source, with the ability to make and install binary packages being something of an afterthought, while Linux packaging like RPM and dpkg and such are designed around the concept of installing a binary package, with building from source as an afterthought. Some of this is historical; binary packaging historically isn't a predominant theme in Unix systems, as I mentioned earlier. For that matter, packaging itself is a more recent thing. Traditionally, you'd deal with uninstalling and such manually.
Now, there are advantages to pre-compiled binaries; mostly time (as in much less), and usually it'll take a lot less space to install a pre-compiled package, than it would to compile the package. There's also advantages to building from source, like avoiding all sorts of library versioning ugliness (my personal pet peeve with binary packages). You can install binary packages on Linux or BSD; you can build from source on Linux or BSD. But the users seem to be biased differently, because the systems are biased differently, because the users are biased differently... it all dovetails.
I guess what's important here is to realize that the difference between ports and RPM's isn't just that ports compile and RPM's just install. Ports are designed to cover the full range of bits and pieces of installing stuff; encoding and tracking and installing dependancies, packaging, installing and deinstalling, local changes necessary to build on your system, compile-time configuration tweaks... all those things. An RPM is just a binary package. If you want to auto-install dependancies, you have to have a higher-level tool like urpmi or apt-get to do it. And, since it's binary, you have to deal with library versioning conflicts, or missing compile options, or any of the other limitations you incur by not building it on your own system.
And further, ports, like the rest of the BSD systems, are centralized. The "ports tree" is really just a big directory tree with a bunch of categorized directories, each containing a Makefile with some variable definitions, a checksum file, a packing list, and various other possible things. Each of those directories represents a single program, which is described by th
Did you know that "FTW" ("for the win") is a direct translation of "Sieg Heil"?