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The return of BSD

What are the BSD flavors and why might you use them?

By Greg Lehey
SunWorld
January  1999
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Abstract
The spotlight is on Linux these days, but what about the other freely available operating systems? In this overview of BSD variants, Greg Lehey runs down the history of the different BSD projects, describes their characteristics, and considers why you might run BSD on your Sun machine or even choose BSD over Linux. (3,000 words)


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It's been a long while, but finally people are coming to accept Solaris, the System V-based operating system that replaced SunOS 4. Still, six years is a long time, and it would have taken much longer if Sun had continued to maintain SunOS 4. Why such loyalty? They are, after all, both versions of Unix.

The last thing I want to do here is revive the SunOS vs. Solaris debate, but I will draw attention to the biggest single difference between SunOS 4 and SunOS 5, the operating system component of today's Solaris: SunOS 4 is based on 4.2 BSD, the version of Unix developed at the University of California at Berkeley and the first operating system with support for TCP/IP. By contrast, SunOS 5 (commonly called Solaris, though that's not quite accurate) is based on AT&T's Unix System V.4. BSD is different enough from System V that six years after the "death" of SunOS 4, it still has a large number of supporters. It's just a pity it doesn't run on modern hardware.

While SunOS 4 doesn't run on modern hardware, other BSD versions do. What's more, they're free. Recent publicity for Linux has tended to obscure the fact that other free operating systems are available. As far back as 1991, before the Linux effort got underway, people at Berkeley were working to release a free version of 4.3 BSD on the Intel platform. In addition, Berkeley Software Design Inc. (BSDI) was working on a commercial version. These efforts were significantly hampered when Unix System Laboratories (USL) filed a lawsuit against BSDI, alleging abuse of AT&T source code.

The lawsuit was resolved in 1994. Only one condition of the settlement was revealed: BSDI pledged to move its codebase to 4.4 BSD Lite, the last version of the BSD line, released just before Berkeley's Computer Sciences Research Group closed down. This version, AT&T agreed, contained none of its code. As such, the free BSD projects also moved to the 4.4 BSD-Lite base.

A modern BSD
One of the main reasons people stopped using SunOS 4 is because it's out of date. In particular, it doesn't support modern hardware. What about the derivatives of 4.4 BSD? Each has its own focus:

BSD/OS
BSD/OS is BSDI's product. It currently runs only on Intel, although attempts have been made to port it to the SPARC architecture. It would appear that BSDI has decided that the SPARC port isn't worthwhile -- more on that later. As the only commercially sold BSD variant, it offers superior vendor support.

FreeBSD
FreeBSD is currently the most widespread of the BSD variants. More than the others, it aims for ease of installation and ease of use for end users. It was originally targeted solely at Intel platforms, but a port for the Compaq/DEC Alpha architecture was recently released. Other projects include a port to UltraSPARC, which hasn't yet made significant headway.

NetBSD
NetBSD takes a different approach: from the beginning, it was intended to support as many hardware platforms as possible. At the time of this writing, it supports just about any platform you can think of, including just about all Sun hardware since the Sun 3, though some support is limited. For example, at the time of this writing the UltraSPARC port doesn't support PCI-based motherboards or multiple processors, though it's likely that support for this hardware will be added in the near future.

OpenBSD
OpenBSD diverged from NetBSD in 1995. Here, more emphasis is placed on security aspects than in the other projects. Like NetBSD, it supports a large number of platforms, though not as many as NetBSD. For example, there is currently no UltraSPARC support.

Why so many?
Looking at this list of operating systems, you may wonder why there are so many similar operating systems. Isn't one enough?

Historically, each project was founded after differences of opinion about what constituted a good operating system. Since the software is free, any group of people can decide to custom build their own operating system. If it doesn't work, they can just stop building. In fact, all current BSD varieties, including BSDI, stem from Bill Jolitz's 386 BSD project, which faded into oblivion in 1994.

On the face of it, this doesn't seem to be a good approach: why not bite the bullet and compromise? In practice, the system shows remarkable self-regulating tendencies: 386 BSD is the only project that has closed up shop, and its descendents are all doing well and actively cross-pollinating. The fact that each version has a different kernel means survival of the fittest applies to kernel code as well, whereas in Linux it applies only to user code. For example, the fledgling FreeBSD SPARC port didn't start from scratch: it started from the NetBSD implementation and immediately raised the question, What can we do better? This process automatically raises the standard necessary for success. As a result, many such attempts fail, but the ones that don't create world-class code.

When choosing a BSD version, you should first consider the platform. In many cases, the platform will determine the choice of operating system. On platforms like the PC, which all BSDs support, the choice may be more difficult, but there isn't really a wrong choice.

What do they taste like?
The biggest difference between the BSDs has nothing to do with the system, but the way in which you use it. Nowadays all workstations use some form of graphical user interface (GUI). All the BSDs include XFree86, the implementation of X11 that is also supplied with Linux. On the one hand, this interface has a strong unifying effect: it's difficult to tell by looking at the screen whether the system is running one of the BSDs, Linux, or even Solaris. On the other hand, the extensive choice of PC hardware makes it relatively difficult to set up X reliably, and it can be worthwhile to spend some time choosing the display hardware for XFree86.

In addition to the choice of hardware, XFree86 offers a bewildering choice of software, in particular display and desktop managers, which makes guessing the underlying platform from the appearance of the screen even more difficult. For further information on window managers, see the Open Directory Project. You can even make it look like OpenWindows with the OpenLook Window Manager.

In many cases, though, you won't want to use a GUI. BSD systems are a particularly good choice for name servers, Web servers, mail servers, news servers -- you name it. This kind of system doesn't require a graphical interface. In fact, it may not even require a display.

What do you get?
All free BSDs are available on CD-ROM, including complete source code and utilities. Many of the utilities are based on the same GNU tools that Linux uses, though a number are also based on older BSD utilities. All include complete software development tools, which again center around the GNU tools. As mentioned, they also include the XFree86 implementation of X11, and most platforms will execute Linux and SCO executables.

In addition, the BSDs come with a large amount of third-party software. We'll look at that below.

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What's it good for?
At first, it would seem that BSD/OS and FreeBSD aren't as interesting as NetBSD and OpenBSD because they don't run on SPARC hardware. In fact, the ability to run on SPARC hardware may be a little overrated. This is probably why BSDI decided to discontinue its SPARC port. There is already one well-maintained operating system for SPARC, Solaris, on which Sun has bet the farm. Although NetBSD and OpenBSD do some things much better than Solaris, it's difficult to compete across the board, and the current state of UltraSPARC support shows a few weaknesses. In particular, PCI support is still under development, and the implementation still doesn't support multiple processors.

In fact, much of the interest of the BSD flavors comes from the low price of PC hardware. If you want to build, say, a large FTP server, you have approximately four choices:

  • Buy a Sun SPARC machine with Solaris 7. It's expensive, but it works, and you won't have much trouble.

  • Buy a PC and install Microsoft software on it. For a large server, you'll need Windows NT. In this particular application, you only need the base NT server software, which at $809 is relatively cheap. Microsoft has a solutions and best practices Web page (see Resources below) that states that you can expect to move about 6 gigabytes (GB) a day from three Compaq ProLiant 5000s or 5500s with four Pentium Pro processors and 512 megabytes (MB) of memory each. In order to maintain availability, Microsoft recommends that you install multiple systems with failover.

  • Buy a PC and install FreeBSD on it. The hardware would appear to cost the same, but you don't pay anything for the software. In fact, as the hardware configuration for wcarchive.cdrom.com shows, this is misleading. wcarchive is only a single system with a single CPU, also a Pentium Pro. In contrast to Microsoft's 6 GB of downloads per day, however, it routinely transfers more than 700 GB of data a day for to up to 3,600 concurrent users. This is over 100 times the performance of three larger Windows NT machines combined. On December 2, 1998, wcarchive transferred 820,097,694,368 bytes of data, making it the busiest FTP server in the world.

  • Buy a PC and install a commercial Unix on it. In many ways, the arguments for FreeBSD also apply to this alternative. But commercial Unix implementations do cost money, and much evidence suggests they can't match the performance BSD supplies.

    wcarchive isn't the only success story for BSD. Another prominent user is Yahoo!, which uses FreeBSD for nearly everything. In addition, at least two of the Internet root name servers run BSD, and most ISPs use BSD for at least some functions.

    In addition to these high-profile applications, NetBSD and OpenBSD are good choices for older Sun hardware, including early SPARC hardware on which Solaris 2 and 7 are too heavy, and Sun 3 systems. The level of support is variable: both NetBSD and OpenBSD contain code for Sun 3, but OpenBSD states that the code isn't actively maintained. Both systems actively support Sun 4, Sun 4c, and Sun 4m systems.

    Why run BSD on a Sun machine? In many cases, the old hardware is more than adequate for a number of functions; you could easily use an old Sun 3 or SPARCstation I as a mail server or a name server. It's also possible to do this with SunOS, but the age of the kernel shows in some aspects of the network stack, and you would have to port all the modern versions of the network clients, which could easily take a multiple of the time it takes to install one of the BSDs with its up-to-date software clients. Ironically, this rejuvenation is most impressive with old PC hardware. Often enough, an old 386 that didn't have enough power to run a single Microsoft desktop suddenly comes back to life as an Internet gateway, mail server, name server and Web server combined.

    Ported software
    Did I say porting? Porting has been a way of life for Unix system administrators for decades, but in the past it was never easy. The FreeBSD Ports Collection (see Resources), which has been adopted by OpenBSD, changes all that. Want to install, say, xarchie, on your system? It's simple: 

    # cd /usr/ports/net/xarchie
# make install

    OK, you'll say, that's easy enough when you have the source installed on your machine. It's not until you discover that the directory hierarchy /usr/ports/net/xarchie contains only six files -- the largest of them 691 bytes long -- that you realize something truly sophisticated must be going on here.

    The FreeBSD Ports Collection currently contains nearly 2,000 ported software products. In each case, it doesn't contain the software itself, just a description of how to obtain the software, how to build it, and how to install it. This gives BSD users easy access to the largest quantity of installable software available for any platform, all at the cost of two commands and a slight delay as the software is loaded from the Internet.

    It's easy to underestimate the advantages of this system. Which version of Sendmail are you running? Chances are it's the version supplied with your system, maybe version 8.8.8 if you upgraded your system recently. The current version, 8.9.1, contains a number of improvements designed to stop mail abuse, in particular by stopping illegal relaying and blocking specific domains. But porting Sendmail has always been a pain, even on the BSD platforms for which it was designed. Use the Ports Collection, on the other hand, and there's nothing to it.

    How about named? A few months back, CERT released an advisory showing that named, the name daemon, was susceptible to various vulnerabilities that affected most Unix systems. By the time the advisory came out, the BSD projects had already produced fixes that addressed the problems; Sun had announced future patches to specific operating system releases only.

    Why BSD and not Linux?
    Linux is much more well known than BSD. Assuming you're going to install a free Unix, why not go with the tide and use Linux?

    There's not really a good answer to that question. Linux is suitable for many of the same functions for which the BSD varieties are suitable. Some people claim BSD is more stable than Linux -- that it's more suited towards server applications, whereas Linux is more suited to the desktop. FreeBSD employs the slogan The Power To Serve.

    Others point to BSD's genuine Unix ancestry, claiming this makes it automatically more mature than Johnny-come-lately Linux. Or they point out that the BSD developers include well-known names from the CSRG in Berkeley, thus implying that the codebase must be better.

    But that's only part of the story, and it's on shaky foundations. The truth is, Linux is a good operating system as well. Like other operating systems, it has its weaknesses and its strengths. Some make the argument that Linux's weaknesses include its virtual memory system, which they claim is a strength of FreeBSD and NetBSD, but no conclusive performance comparisons have been made.

    One difference between the BSDs and Linux is standpoint. Linux started as a grassroots development, just like the BSDs, but in the last year or two it has become increasingly commercial. One of the reasons you hear so much about Linux is because people are making money selling it. The BSDs are less focused on commercial sales.

    So why BSD? Well, for one thing, it comes from the same codebase that's running on your Solaris machines, so it's likely to feel more familiar. And, while there's no hard evidence that BSD is more reliable or performs better than Linux, there are surprisingly few claims to the contrary from the Linux camp.

    Getting BSD
    FreeBSD, NetBSD, and OpenBSD are freely redistributable, and you can download them via the Internet. This may not be the best alternative, though, because the distributions are large, and network problems can make this form of installation less than straightforward. All three operating systems are available on CD-ROM, and the FreeBSD distribution is available with a book The Complete FreeBSD, which covers all aspects of installation and system administration by which FreeBSD differs from other Unix variants.

    What about support?
    The big argument against using free operating systems in commercial environments is support. Who do you call if something goes wrong? In this respect, the free BSDs don't differ greatly from Linux. Some commercial support is available, and more is becoming available. One difference, though, is that there is also a commercial BSD: BSD/OS comes with support options comparable to those of other Unix flavors.

    Traditionally, free operating systems have been tech-supported via mailing lists in which volunteers answer questions, usually correctly. The problem here is with the word usually. How can you tell if the advice you're given is correct? The alternative is to enlist the aid of commercial support organizations, reachable via the Web sites of the individual projects.

    That's a wrap; now go check out the BSDs for yourselves!


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    Greg Lehey's photo About the author
    Greg Lehey is an independent computer consultant and author specializing in BSD Unix. Based in Adelaide, Australia, he is the author of Porting Unix Software (O'Reilly and Associates, 1995), Installing and Running FreeBSD (Walnut Creek, 1996), and The Complete FreeBSD (Walnut Creek, 1997 and 1998). Reach Greg at greg.lehey@sunworld.com.

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