From 12450ef32d8b7a349f3b973cd8adef46bcf40b31 Mon Sep 17 00:00:00 2001 From: Nik Clayton Date: Wed, 14 Mar 2001 18:10:08 +0000 Subject: [PATCH] Add "Explaining BSD", an article by Greg Lehey. --- .../articles/explaining-bsd/Makefile | 23 + .../articles/explaining-bsd/article.sgml | 542 ++++++++++++++++++ .../articles/explaining-bsd/Makefile | 23 + .../articles/explaining-bsd/article.sgml | 542 ++++++++++++++++++ 4 files changed, 1130 insertions(+) create mode 100644 en_US.ISO8859-1/articles/explaining-bsd/Makefile create mode 100644 en_US.ISO8859-1/articles/explaining-bsd/article.sgml create mode 100644 en_US.ISO_8859-1/articles/explaining-bsd/Makefile create mode 100644 en_US.ISO_8859-1/articles/explaining-bsd/article.sgml diff --git a/en_US.ISO8859-1/articles/explaining-bsd/Makefile b/en_US.ISO8859-1/articles/explaining-bsd/Makefile new file mode 100644 index 0000000000..3893643f3e --- /dev/null +++ b/en_US.ISO8859-1/articles/explaining-bsd/Makefile @@ -0,0 +1,23 @@ +# +# $FreeBSD: doc/en_US.ISO_8859-1/articles/freebsd-questions/Makefile,v 1.1 2001/02/16 00:22:33 nik Exp $ +# + +MAINTAINER=grog@FreeBSD.org + +DOC?= article + +FORMATS?= html + +INSTALL_COMPRESSED?= gz +INSTALL_ONLY_COMPRESSED?= + +# +# SRCS lists the individual SGML files that make up the document. Changes +# to any of these files will force a rebuild +# + +# SGML content +SRCS= article.sgml + +DOC_PREFIX?= ${.CURDIR}/../../.. +.include "${DOC_PREFIX}/share/mk/doc.project.mk" diff --git a/en_US.ISO8859-1/articles/explaining-bsd/article.sgml b/en_US.ISO8859-1/articles/explaining-bsd/article.sgml new file mode 100644 index 0000000000..ad1ba6cec5 --- /dev/null +++ b/en_US.ISO8859-1/articles/explaining-bsd/article.sgml @@ -0,0 +1,542 @@ + +%man; +]> + +
+ + Explaining BSD + + + Greg + Lehey + + +
grog@FreeBSD.org
+ + + + + In the open source world, the word Linux is almost + synonymous with Operating System, but it's not the only + open source UNIX operating system. According + to the Internet + Operating System Counter, as of April 1999 31.3% of the + world's network connected machines run Linux. 14.6% run BSD UNIX. + Some of the world's largest web operations, such as Yahoo!, run BSD. The world's + busiest ftp server, ftp.cdrom.com, uses BSD to + transfer 1.4 TB of data a day. Clearly this is not a niche + market: BSD is a well-kept secret. + + So what's the secret? Why isn't BSD better known? This white + paper addresses these and other questions. + + Throughout this paper, differences between BSD and Linux will be + noted like this. + + + + + What is BSD? + + BSD stands for Berkeley Software Distribution. It is + the name of distributions of source code from the University of + California, Berkeley, which were originally extensions to AT&T's + Research UNIX operating system. Several open source operating system + projects are based on a release of this source code known as + 4.4BSD-Lite. In addition, they comprise a number of packages from other + Open Source projects, including notably the GNU project. The overall + operating system comprises: + + + + The BSD kernel, which handles process scheduling, memory + management, symmetric multi-processing (SMP), device drivers, + etc. + + Unlike the Linux kernel, there are several different + BSD kernels with differing capabilities. + + + + The C library, the base API for the system. + + The BSD C library is based on code from Berkeley, not + the GNU project. + + + + Utilities such as shells, file utilities, compilers and + linkers. + + Some of the utilities are derived from the GNU + project, others are not. + + + + The X Window system, which handles graphical display. + + The X Window system used in most versions of BSD is maintained + by a separate project, the + XFree86 project. + This is the same code as Linux uses. BSD does not normally + specify a graphical desktop such as GNOME or KDE, + though these are available. + + + + Many other programs and utilities. + + + + + + What, a real UNIX? + + The BSD operating systems are not clones, but open source + derivatives of AT&T's Research UNIX operating system, which is also + the ancestor of the modern UNIX System V. This may surprise you. How + could that happen when AT&T has never released its code as open + source? + + It's true that AT&T UNIX is not open source, and in a copyright + sense BSD is very definitely not UNIX, but on the + other hand, AT&T has imported sources from other projects, + noticeably the Computer Sciences Research Group of the University of + California in Berkeley, CA. Starting in 1976, the CSRG started + releasing tapes of their software, calling them Berkeley + Software Distribution or BSD. + + Initial BSD releases consisted mainly of user programs, but that + changed dramatically when the CSRG landed a contract with the Defense + Advanced Projects Research Agency (DARPA) to upgrade the communications + protocols on their network, ARPANET. The new protocols were known as + the Internet Protocols, later + TCP/IP after the most important protocols. The + first widely distributed implementation was part of 4.2BSD, in + 1982. + + In the course of the 1980s, a number of new workstation companies + sprang up. Many preferred to license UNIX rather than developing + operating systems for themselves. In particular, Sun Microsystems + licensed UNIX and implemented a version of 4.2BSD, which they called + SunOS. When AT&T themselves were allowed to sell UNIX commercially, + they started with a somewhat bare-bones implementation called System + III, to be quickly followed by System V. The System V code base did not + include networking, so all implementions included additional software + from the BSD, including the TCP/IP software, but also utilities such as + the csh shell and the vi + editor. Collectively, these enhancements were known as the + Berkeley Extensions. + + The BSD tapes contained AT&T source code and thus required a + UNIX source license. By 1990, the CSRG's funding was running out, and + it faced closure. Some members of the group decided to release the BSD + code, which was Open Source, without the AT&T proprietary code. + This finally happened with the Networking Tape 2, + usually known as Net/2. Net/2 was not a complete + operating system: about 20% of the kernel code was missing. One of the + CSRG members, William F. Jolitz, wrote the remaining code and released + it in early 1992 as 386BSD. At the same time, + another group of ex-CSRG members formed a commercial company called + Berkeley Software Design Inc. + and released a beta version of an operating system called + BSD/386, which was based on + the same sources. The name of the operating system has since changed + to BSD/OS. + + 386BSD never became a stable operating system. Instead, two other + projects split off from it in 1993: + NetBSD and + FreeBSD. The two projects + originally diverged due to differences in patience waiting for + improvements to 386BSD: the NetBSD people started early in the year, + and the first version of FreeBSD wasn't ready until the end of the + year. In the meantime, the code base had diverged sufficiently to + make it difficult to merge. In addition, the projects had different + aims, as we'll see below. In 1996, a further project, + OpenBSD, split off from + NetBSD. + + + + Why isn't BSD better known? + + For a number of reasons, BSD is relatively unknown: + + + + The BSD developers are often more interested in polishing their + code than marketing it. + + + + Much of Linux's popularity is due to factors external to the + Linux projects, such as the press, and to companies formed to + provide Linux services. Until recently, the open source BSDs had no + such proponents. + + + + BSD developers tend to be more experienced than Linux + developers, and have less interest in making the system easy to use. + Newcomers tend to feel more comfortable with Linux. + + + + In 1992, AT&T sued + BSDI, + the vendor of BSD/386, alleging that the product contained + AT&T-copyrighted code. The case was settled out of court in + 1994, but the spectre of the litigation continues to haunt people. + As recently as March 2000 an article published on the web claimed + that the court case had been recently settled. + + One detail that the lawsuit did clarify is the naming: in the + 1980s, BSD was known as BSD UNIX. With the + elimination of the last vestige of AT&T code from BSD, it + also lost the right to the name UNIX. Thus you will see + references in book titles to the 4.3BSD UNIX operating + system and the 4.4BSD operating + system. + + + + There is a perception that the BSD projects are fragmented and + belligerent. The + Wall Street + Journal spoke of balkanization of the + BSD projects. Like the law suit, this perception bases mainly + on ancient history. + + + + + + Comparing BSD and Linux + + So what's really the difference between, say, Debian Linux and + FreeBSD? For the average user, the difference is surprisingly small: + Both are UNIX-like operating systems. Both are developed by + non-commercial projects (this doesn't apply to many other Linux + distributions, of course). In the following section, we'll look at BSD + and compare it to Linux. The description applies most closely to + FreeBSD, which accounts for an estimated 80% of the BSD installations, + but the differences from NetBSD and OpenBSD are small. + + + Who owns BSD? + + No one person or corporation owns BSD. It is created and + distributed by a community of highly technical and committed + contributors all over the world. Some of the components of BSD are + Open Source projects managed by a different project maintainer. + + + + How is BSD developed and updated? + + The BSD kernels are developed and updated following the Open + Source development model. Each project maintains a publicly + accessible source tree under the + Concurrent Versions + System (CVS), which contains all source files for the + project, including documentation and other incidental files. CVS + allows users to check out (in other words, to + extract a copy of) any desired version of the system. + + A large number of developers worldwide contribute to improvements + to BSD. They are divided into three kinds: + + + + Contributors write code or documentation. + They are not permitted to commit (add code) directly to the source + tree. In order for their code to be included in the system, it + must be reviewed and checked in by a registered developer, known + as a committer. + + + + Committers are developers with write + access to the source tree. In order to become a committer, an + individual must show ability in the area in which he is + active. + + + It is at the individual committer's discretion whether he should + obtain authority before committing changes to the source tree. In + general, an experienced committer may make changes which are + obviously correct without obtaining consensus. For example, a + documentation project committer may correct typographical or + grammatical errors without review. On the other hand, developers + making far-reaching or complicated changes are expected to submit + their changes for review before committing them. In extreme + cases, a core team member with a function such as Principal + Architect may order that changes be removed from the tree, a + process known as backing out. All committers + receive mail describing each individual commit, so it is not + possible to commit secretly. + + + + Core team In addition, FreeBSD + and NetBSD each have a core team which manages the project. The + core teams developed in the course of the projects, and their role + is not always well-defined. It is not necessary to be a developer + in order to be a core team member, though it is normal. The rules + for the core team vary from one project to the other, but in + general they have more say in the direction of the project than + non-core team members have. + + + + This arrangement differs from Linux in a number of ways: + + + + No one person controls the content of the system. In + practice, this difference is overrated, since the Chief Architect + can require that code be backed out, and even in the Linux project + several people are permitted to make changes. + + + + On the other hand, there is a central + repository, a single place where you can find the entire operating + system sources, including all older versions. + + + + BSD projects maintain the entire Operating + System, not only the kernel. This distinction is only + marginally useful: neither BSD nor Linux is useful without + applications. The applications used under BSD are frequently the + same as the applications used under Linux. + + + + As a result of the formalized maintenance of a single CVS + source tree, BSD development is clear, and it is possible to + access any version of the system by release number or by date. + CVS also allows incremental updates to the system: for example, + the FreeBSD repository is updated about 100 times a day. Most of + these changes are small. + + + + + + BSD releases + + Each BSD project provides the system in three different + releases. As with Linux, releases are assigned a + number such as 1.4.1 or 3.5. In addition, the version number has a + suffix indicating its purpose: + + + + The development version of the system is called + CURRENT. FreeBSD assigns a number to + CURRENT, for example FreeBSD 5.0-CURRENT. NetBSD uses a slightly + different naming scheme and appends a single-letter suffix which + indicates changes in the internal interfaces, for example NetBSD + 1.4.3G. OpenBSD does not assign a number ("OpenBSD-current"). + All new development on the system goes into this branch. + + + + At regular intervals, between two and four times a year, the + projects bring out a RELEASE version of the + system, which is available on CD-ROM and for free download from + ftp sites, for example OpenBSD 2.6-RELEASE or NetBSD 1.4-RELEASE. + The RELEASE version is intended for end users and is the normal + version of the system. NetBSD also provides patch + releases with a third digit, for example NetBSD + 1.4.2. + + + + As bugs are found in a RELEASE version, they are fixed, and + the fixes are added to the CVS tree. In FreeBSD, the resultant + version is called the STABLE version, while in NetBSD and OpenBSD + it continues to be called the RELEASE version. Smaller new + features can also be added to this branch after a period of test + in the CURRENT branch. + + + + By contrast, Linux maintains two separate code trees: + the stable version and the development version. Stable versions + have an even minor version number, such as 2.0, 2.2 or 2.4. + Development versions have an odd minor version number, such as 2.1, + 2.3 or 2.5. In each case, the number is followed by a further + number designating the exact release. In addition, each vendor adds + their own userland programs and utilities, so the name of the + distribution is also important. Each distribution vendor also + assigns version numbers to the distribution, so a complete + description might be something like TurboLinux 6.0 with kernel + 2.2.14 + + + + What versions of BSD are available? + + In contrast to the numerous Linux distributions, there are only + three open source BSDs. Each BSD project maintains its own source + tree and its own kernel. In practice, though, there appear to be + fewer divergences between the userland code of the projects than there + is in Linux. + + It's difficult to categorize the goals of each project: the + differences are very subjective. Basically, + + + + FreeBSD aims for high performance and ease of use by + end users, and is a favourite of web content providers. It runs + on PCs and Compaq's Alpha processors. The FreeBSD project has + significantly more users than the other projects. + + + + NetBSD aims for maximum portability: of course it runs + NetBSD. It runs on machines from palmtops to large + servers, and has even been used on NASA space missions. It is a + particularly good choice for running on old non-Intel + hardware. + + + + OpenBSD aims for security and code purity: it uses a + combination of the open source concept and rigorous code reviews + to create a system which is demonstrably correct, making it the + choice of security-conscious organizations such as banks, stock + exchanges and US Government departments. Like NetBSD, it runs on + a number of platforms. + + + + There are also two additional BSD operating systems which are not + open source, BSD/OS and Apple's Mac OS X: + + + + BSD/OS is the oldest of the 4.4BSD derivatives. It + is not open source, though source code licenses are available at + relatively low cost. It resembles FreeBSD in many ways. + + + + Mac OS + X is the latest version of the operating system for + Apple Computer Inc.'s + Macintosh line. Unlike the rest of the operating system, the + kernel is open source. As part of this development, key Apple + developers have commit access to the FreeBSD source tree. + + + + + + How does the BSD license differ from the GNU Public + license? + + Linux is available under the + GNU General Public + License (GPL), which is designed to eliminate closed + source software. In particular, any derivative work of a product + released under the GPL must also be supplied with source code if + requested. By contrast, the + BSD + license is less restrictive: binary-only distributions are + allowed. This is particularly attractive for embedded + applications. + + + + What else should I know? + + Since fewer applications are available for BSD than Linux, the BSD + developers created a Linux compatibility package, which allows Linux + programs to run under BSD. The package includes both kernel + modifications, in order to correctly perform Linux system calls, and + Linux compatibility files such as the C library. There is no + noticeable difference in execution speed between a Linux application + running on a Linux machine and a Linux application running on a BSD + machine of the same speed. + + The all from one supplier nature of BSD means that + upgrades are much easier to handle than is frequently the case with + Linux. BSD handles library version upgrades by providing + compatibility modules for earlier library versions, so it is possible + to run binaries which are several years old with no problems. + + + + Which should I use, BSD or Linux? + + What does this all mean in practice? Who should use BSD, who + should use Linux? + + This is a very difficult question to answer. Here are some + guidelines: + + + + If it ain't broke, don't fix it: If you already + use an open source operating system, and you are happy with it, + there's probably no good reason to change. + + + + BSD systems, in particular FreeBSD, can have notably higher + performance than Linux. But this isn't across the board. In many + cases, there is little or no difference in performance. In some + cases, Linux may perform better than FreeBSD. + + + + In general, BSD systems have a better reputation for + reliability, mainly as a result of the more mature code + base. + + + + The BSD license may be more attractive than the GPL. + + + + BSD can execute Linux code, while Linux can't execute BSD + code. As a result, more software is available for BSD than for + Linux. + + + + + + Who provides support, service, and training for BSD? + + BSDi have always supported BSD/OS, and they have recently + announced support contracts for FreeBSD. + + In addition, each of the projects has a list of consultants for + hire: + FreeBSD, + NetBSD, + and OpenBSD. + + +
+ + diff --git a/en_US.ISO_8859-1/articles/explaining-bsd/Makefile b/en_US.ISO_8859-1/articles/explaining-bsd/Makefile new file mode 100644 index 0000000000..3893643f3e --- /dev/null +++ b/en_US.ISO_8859-1/articles/explaining-bsd/Makefile @@ -0,0 +1,23 @@ +# +# $FreeBSD: doc/en_US.ISO_8859-1/articles/freebsd-questions/Makefile,v 1.1 2001/02/16 00:22:33 nik Exp $ +# + +MAINTAINER=grog@FreeBSD.org + +DOC?= article + +FORMATS?= html + +INSTALL_COMPRESSED?= gz +INSTALL_ONLY_COMPRESSED?= + +# +# SRCS lists the individual SGML files that make up the document. Changes +# to any of these files will force a rebuild +# + +# SGML content +SRCS= article.sgml + +DOC_PREFIX?= ${.CURDIR}/../../.. +.include "${DOC_PREFIX}/share/mk/doc.project.mk" diff --git a/en_US.ISO_8859-1/articles/explaining-bsd/article.sgml b/en_US.ISO_8859-1/articles/explaining-bsd/article.sgml new file mode 100644 index 0000000000..ad1ba6cec5 --- /dev/null +++ b/en_US.ISO_8859-1/articles/explaining-bsd/article.sgml @@ -0,0 +1,542 @@ + +%man; +]> + +
+ + Explaining BSD + + + Greg + Lehey + + +
grog@FreeBSD.org
+ + + + + In the open source world, the word Linux is almost + synonymous with Operating System, but it's not the only + open source UNIX operating system. According + to the Internet + Operating System Counter, as of April 1999 31.3% of the + world's network connected machines run Linux. 14.6% run BSD UNIX. + Some of the world's largest web operations, such as Yahoo!, run BSD. The world's + busiest ftp server, ftp.cdrom.com, uses BSD to + transfer 1.4 TB of data a day. Clearly this is not a niche + market: BSD is a well-kept secret. + + So what's the secret? Why isn't BSD better known? This white + paper addresses these and other questions. + + Throughout this paper, differences between BSD and Linux will be + noted like this. + + + + + What is BSD? + + BSD stands for Berkeley Software Distribution. It is + the name of distributions of source code from the University of + California, Berkeley, which were originally extensions to AT&T's + Research UNIX operating system. Several open source operating system + projects are based on a release of this source code known as + 4.4BSD-Lite. In addition, they comprise a number of packages from other + Open Source projects, including notably the GNU project. The overall + operating system comprises: + + + + The BSD kernel, which handles process scheduling, memory + management, symmetric multi-processing (SMP), device drivers, + etc. + + Unlike the Linux kernel, there are several different + BSD kernels with differing capabilities. + + + + The C library, the base API for the system. + + The BSD C library is based on code from Berkeley, not + the GNU project. + + + + Utilities such as shells, file utilities, compilers and + linkers. + + Some of the utilities are derived from the GNU + project, others are not. + + + + The X Window system, which handles graphical display. + + The X Window system used in most versions of BSD is maintained + by a separate project, the + XFree86 project. + This is the same code as Linux uses. BSD does not normally + specify a graphical desktop such as GNOME or KDE, + though these are available. + + + + Many other programs and utilities. + + + + + + What, a real UNIX? + + The BSD operating systems are not clones, but open source + derivatives of AT&T's Research UNIX operating system, which is also + the ancestor of the modern UNIX System V. This may surprise you. How + could that happen when AT&T has never released its code as open + source? + + It's true that AT&T UNIX is not open source, and in a copyright + sense BSD is very definitely not UNIX, but on the + other hand, AT&T has imported sources from other projects, + noticeably the Computer Sciences Research Group of the University of + California in Berkeley, CA. Starting in 1976, the CSRG started + releasing tapes of their software, calling them Berkeley + Software Distribution or BSD. + + Initial BSD releases consisted mainly of user programs, but that + changed dramatically when the CSRG landed a contract with the Defense + Advanced Projects Research Agency (DARPA) to upgrade the communications + protocols on their network, ARPANET. The new protocols were known as + the Internet Protocols, later + TCP/IP after the most important protocols. The + first widely distributed implementation was part of 4.2BSD, in + 1982. + + In the course of the 1980s, a number of new workstation companies + sprang up. Many preferred to license UNIX rather than developing + operating systems for themselves. In particular, Sun Microsystems + licensed UNIX and implemented a version of 4.2BSD, which they called + SunOS. When AT&T themselves were allowed to sell UNIX commercially, + they started with a somewhat bare-bones implementation called System + III, to be quickly followed by System V. The System V code base did not + include networking, so all implementions included additional software + from the BSD, including the TCP/IP software, but also utilities such as + the csh shell and the vi + editor. Collectively, these enhancements were known as the + Berkeley Extensions. + + The BSD tapes contained AT&T source code and thus required a + UNIX source license. By 1990, the CSRG's funding was running out, and + it faced closure. Some members of the group decided to release the BSD + code, which was Open Source, without the AT&T proprietary code. + This finally happened with the Networking Tape 2, + usually known as Net/2. Net/2 was not a complete + operating system: about 20% of the kernel code was missing. One of the + CSRG members, William F. Jolitz, wrote the remaining code and released + it in early 1992 as 386BSD. At the same time, + another group of ex-CSRG members formed a commercial company called + Berkeley Software Design Inc. + and released a beta version of an operating system called + BSD/386, which was based on + the same sources. The name of the operating system has since changed + to BSD/OS. + + 386BSD never became a stable operating system. Instead, two other + projects split off from it in 1993: + NetBSD and + FreeBSD. The two projects + originally diverged due to differences in patience waiting for + improvements to 386BSD: the NetBSD people started early in the year, + and the first version of FreeBSD wasn't ready until the end of the + year. In the meantime, the code base had diverged sufficiently to + make it difficult to merge. In addition, the projects had different + aims, as we'll see below. In 1996, a further project, + OpenBSD, split off from + NetBSD. + + + + Why isn't BSD better known? + + For a number of reasons, BSD is relatively unknown: + + + + The BSD developers are often more interested in polishing their + code than marketing it. + + + + Much of Linux's popularity is due to factors external to the + Linux projects, such as the press, and to companies formed to + provide Linux services. Until recently, the open source BSDs had no + such proponents. + + + + BSD developers tend to be more experienced than Linux + developers, and have less interest in making the system easy to use. + Newcomers tend to feel more comfortable with Linux. + + + + In 1992, AT&T sued + BSDI, + the vendor of BSD/386, alleging that the product contained + AT&T-copyrighted code. The case was settled out of court in + 1994, but the spectre of the litigation continues to haunt people. + As recently as March 2000 an article published on the web claimed + that the court case had been recently settled. + + One detail that the lawsuit did clarify is the naming: in the + 1980s, BSD was known as BSD UNIX. With the + elimination of the last vestige of AT&T code from BSD, it + also lost the right to the name UNIX. Thus you will see + references in book titles to the 4.3BSD UNIX operating + system and the 4.4BSD operating + system. + + + + There is a perception that the BSD projects are fragmented and + belligerent. The + Wall Street + Journal spoke of balkanization of the + BSD projects. Like the law suit, this perception bases mainly + on ancient history. + + + + + + Comparing BSD and Linux + + So what's really the difference between, say, Debian Linux and + FreeBSD? For the average user, the difference is surprisingly small: + Both are UNIX-like operating systems. Both are developed by + non-commercial projects (this doesn't apply to many other Linux + distributions, of course). In the following section, we'll look at BSD + and compare it to Linux. The description applies most closely to + FreeBSD, which accounts for an estimated 80% of the BSD installations, + but the differences from NetBSD and OpenBSD are small. + + + Who owns BSD? + + No one person or corporation owns BSD. It is created and + distributed by a community of highly technical and committed + contributors all over the world. Some of the components of BSD are + Open Source projects managed by a different project maintainer. + + + + How is BSD developed and updated? + + The BSD kernels are developed and updated following the Open + Source development model. Each project maintains a publicly + accessible source tree under the + Concurrent Versions + System (CVS), which contains all source files for the + project, including documentation and other incidental files. CVS + allows users to check out (in other words, to + extract a copy of) any desired version of the system. + + A large number of developers worldwide contribute to improvements + to BSD. They are divided into three kinds: + + + + Contributors write code or documentation. + They are not permitted to commit (add code) directly to the source + tree. In order for their code to be included in the system, it + must be reviewed and checked in by a registered developer, known + as a committer. + + + + Committers are developers with write + access to the source tree. In order to become a committer, an + individual must show ability in the area in which he is + active. + + + It is at the individual committer's discretion whether he should + obtain authority before committing changes to the source tree. In + general, an experienced committer may make changes which are + obviously correct without obtaining consensus. For example, a + documentation project committer may correct typographical or + grammatical errors without review. On the other hand, developers + making far-reaching or complicated changes are expected to submit + their changes for review before committing them. In extreme + cases, a core team member with a function such as Principal + Architect may order that changes be removed from the tree, a + process known as backing out. All committers + receive mail describing each individual commit, so it is not + possible to commit secretly. + + + + Core team In addition, FreeBSD + and NetBSD each have a core team which manages the project. The + core teams developed in the course of the projects, and their role + is not always well-defined. It is not necessary to be a developer + in order to be a core team member, though it is normal. The rules + for the core team vary from one project to the other, but in + general they have more say in the direction of the project than + non-core team members have. + + + + This arrangement differs from Linux in a number of ways: + + + + No one person controls the content of the system. In + practice, this difference is overrated, since the Chief Architect + can require that code be backed out, and even in the Linux project + several people are permitted to make changes. + + + + On the other hand, there is a central + repository, a single place where you can find the entire operating + system sources, including all older versions. + + + + BSD projects maintain the entire Operating + System, not only the kernel. This distinction is only + marginally useful: neither BSD nor Linux is useful without + applications. The applications used under BSD are frequently the + same as the applications used under Linux. + + + + As a result of the formalized maintenance of a single CVS + source tree, BSD development is clear, and it is possible to + access any version of the system by release number or by date. + CVS also allows incremental updates to the system: for example, + the FreeBSD repository is updated about 100 times a day. Most of + these changes are small. + + + + + + BSD releases + + Each BSD project provides the system in three different + releases. As with Linux, releases are assigned a + number such as 1.4.1 or 3.5. In addition, the version number has a + suffix indicating its purpose: + + + + The development version of the system is called + CURRENT. FreeBSD assigns a number to + CURRENT, for example FreeBSD 5.0-CURRENT. NetBSD uses a slightly + different naming scheme and appends a single-letter suffix which + indicates changes in the internal interfaces, for example NetBSD + 1.4.3G. OpenBSD does not assign a number ("OpenBSD-current"). + All new development on the system goes into this branch. + + + + At regular intervals, between two and four times a year, the + projects bring out a RELEASE version of the + system, which is available on CD-ROM and for free download from + ftp sites, for example OpenBSD 2.6-RELEASE or NetBSD 1.4-RELEASE. + The RELEASE version is intended for end users and is the normal + version of the system. NetBSD also provides patch + releases with a third digit, for example NetBSD + 1.4.2. + + + + As bugs are found in a RELEASE version, they are fixed, and + the fixes are added to the CVS tree. In FreeBSD, the resultant + version is called the STABLE version, while in NetBSD and OpenBSD + it continues to be called the RELEASE version. Smaller new + features can also be added to this branch after a period of test + in the CURRENT branch. + + + + By contrast, Linux maintains two separate code trees: + the stable version and the development version. Stable versions + have an even minor version number, such as 2.0, 2.2 or 2.4. + Development versions have an odd minor version number, such as 2.1, + 2.3 or 2.5. In each case, the number is followed by a further + number designating the exact release. In addition, each vendor adds + their own userland programs and utilities, so the name of the + distribution is also important. Each distribution vendor also + assigns version numbers to the distribution, so a complete + description might be something like TurboLinux 6.0 with kernel + 2.2.14 + + + + What versions of BSD are available? + + In contrast to the numerous Linux distributions, there are only + three open source BSDs. Each BSD project maintains its own source + tree and its own kernel. In practice, though, there appear to be + fewer divergences between the userland code of the projects than there + is in Linux. + + It's difficult to categorize the goals of each project: the + differences are very subjective. Basically, + + + + FreeBSD aims for high performance and ease of use by + end users, and is a favourite of web content providers. It runs + on PCs and Compaq's Alpha processors. The FreeBSD project has + significantly more users than the other projects. + + + + NetBSD aims for maximum portability: of course it runs + NetBSD. It runs on machines from palmtops to large + servers, and has even been used on NASA space missions. It is a + particularly good choice for running on old non-Intel + hardware. + + + + OpenBSD aims for security and code purity: it uses a + combination of the open source concept and rigorous code reviews + to create a system which is demonstrably correct, making it the + choice of security-conscious organizations such as banks, stock + exchanges and US Government departments. Like NetBSD, it runs on + a number of platforms. + + + + There are also two additional BSD operating systems which are not + open source, BSD/OS and Apple's Mac OS X: + + + + BSD/OS is the oldest of the 4.4BSD derivatives. It + is not open source, though source code licenses are available at + relatively low cost. It resembles FreeBSD in many ways. + + + + Mac OS + X is the latest version of the operating system for + Apple Computer Inc.'s + Macintosh line. Unlike the rest of the operating system, the + kernel is open source. As part of this development, key Apple + developers have commit access to the FreeBSD source tree. + + + + + + How does the BSD license differ from the GNU Public + license? + + Linux is available under the + GNU General Public + License (GPL), which is designed to eliminate closed + source software. In particular, any derivative work of a product + released under the GPL must also be supplied with source code if + requested. By contrast, the + BSD + license is less restrictive: binary-only distributions are + allowed. This is particularly attractive for embedded + applications. + + + + What else should I know? + + Since fewer applications are available for BSD than Linux, the BSD + developers created a Linux compatibility package, which allows Linux + programs to run under BSD. The package includes both kernel + modifications, in order to correctly perform Linux system calls, and + Linux compatibility files such as the C library. There is no + noticeable difference in execution speed between a Linux application + running on a Linux machine and a Linux application running on a BSD + machine of the same speed. + + The all from one supplier nature of BSD means that + upgrades are much easier to handle than is frequently the case with + Linux. BSD handles library version upgrades by providing + compatibility modules for earlier library versions, so it is possible + to run binaries which are several years old with no problems. + + + + Which should I use, BSD or Linux? + + What does this all mean in practice? Who should use BSD, who + should use Linux? + + This is a very difficult question to answer. Here are some + guidelines: + + + + If it ain't broke, don't fix it: If you already + use an open source operating system, and you are happy with it, + there's probably no good reason to change. + + + + BSD systems, in particular FreeBSD, can have notably higher + performance than Linux. But this isn't across the board. In many + cases, there is little or no difference in performance. In some + cases, Linux may perform better than FreeBSD. + + + + In general, BSD systems have a better reputation for + reliability, mainly as a result of the more mature code + base. + + + + The BSD license may be more attractive than the GPL. + + + + BSD can execute Linux code, while Linux can't execute BSD + code. As a result, more software is available for BSD than for + Linux. + + + + + + Who provides support, service, and training for BSD? + + BSDi have always supported BSD/OS, and they have recently + announced support contracts for FreeBSD. + + In addition, each of the projects has a list of consultants for + hire: + FreeBSD, + NetBSD, + and OpenBSD. + + +
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