FreeBSD Introduction from "FreeBSD Using Daquan" Wang Bo is in the computer field, UNIX has always been as a high-end platform. A few years ago, only in the special equipment room of large agencies can be exposed to them, even a slightly small institutions are not affordable to buy UNIX workstations. Only few users have the opportunity to contact and use UNIX, computer professionals who can manage and maintain UNIX systems, which makes Unix always covers a mysterious veil, in front of ordinary users, UNIX It belongs to an operating system that is difficult to use and very expensive. However, this situation has changed after the free Unix system running on a personal computer appears. In fact, today's UNIX can't be said to be a single operating system, which includes a lot of types, high-end HP, Sun servers, and unix systems running on the Intel platform. UNIX is no longer an operating system that ordinary users is expensive. Everyone who loves UNIX can install a set of UNIX systems in their own PCs, learn it, use it. SMEs can also use the PC server to run the UNIX system to make full use of the powerful processing power of the UNIX system. FreeBSD is a UNIX system running freely on the Intel platform, which can be available free of charge on the Internet. It has an extremely excellent performance, making it recognized by computer researchers and network professionals. Therefore, not only professional researchers use it as a UNIX workstation, many companies, especially ISP (Internet Service Providers), but use high-end PC servers running FreeBSD to provide network services for their many users. FreeBSD's origins have created UNIX since the 1969 AT & T Bell Laboratory, UNIX has continued to develop and gradually become a mainstream operating system. Although the current Windows series has occupied the field of desktop computers, the Windows NT server is also recognized by some users in the network server, but in the field of high-end workstations and servers, UNIX still has an irreplaceable role. Especially in terms of use as Internet servers, UNIX's high performance, high reliability, and highly scalable capabilities remain instead of other operating systems. Although UNIX creates by AT & T, it is so popular but does not completely attributes AT & T's own credits. Modern UNIX is not a manufacturer's alone product, which has formed a variety of different versions during its long-term development. However, it is rich and diverse, so that UNIX has powerful vitality. FreeBSD is a quite excellent branch in many branches in UNIX. Its development history is also quite a long. It is a successor of the famous BSD UNIX. Therefore, we must understand the history of FreeBSD development. First, we must understand the process of UNIX development. UNIX's historical development
The Historical Rossing of the UNIX operating system, its first version is 1969 by Ken Thompson in the AT & T Bel laboratory, running on a DEC PDP-7 computer. This system is very rough, far from modern Unix, which has only some of the most basic features of the operating system. Later, Ken Thompson and Dennis Ritchie were processed and written throughout the system using the C language, making UNIX to easily transplant to other hardware computers. Since then, UNIX systems have started remarkable development. Since At this time, AT & T has not made Unix as its official item, the researchers are only used in the laboratory and perfect it. It is because UNIX is a computer researcher as a research project, other research institutions and universities, I hope to get this system for their own research. AT & T takes only a small fee for UNIX, union, and the research institutions to obtain UNIX source code for UNIX. The Source code of UNIX is distributed into each university. On the other hand, the researchers can improve the system as needed, or in other hardware environments, on the other hand, there is a large number of students who understand UNIX usage and programming, which makes Unix has a wide range of popularity. Since the development of the operating system is quite difficult, only a small number of computer vendors, such as IBM, Digital and other large companies have their own operating systems, while other many manufacturing hardware vendors use others to develop operating systems. Because Unix doesn't need too much cost, many vendors have chosen UNIX as the operating system used by the computer they produce. They transplanted UNIX in their hardware environment without having to develop an operating system from the head. By the end of the 1970s, after UNIX developed to version 6, AT & T realized the value of UNIX, established UNIX System Lab, USL, continued to develop UNIX. Therefore, the AT & T side continues to develop the internal Unix version 7 on the other side, and on the one hand, the USL is developed from the officially released UNIX version, while AT & T also announces ownership to UNIX products. Almost at the same time, California University Berkeley Branch Computer System Research Group (CSRG) uses UNIX to study the operating system, so their research results are reflected in the UNIX they use. They have considerable improvements in UNIX, adding a lot of advanced features, including better memory management, fast and robust file systems, etc., most original source code has been rereaded to support these new features. . Many other UNIX users, including other universities and business, I hope to get CSRG improved UNIX systems. Therefore, researchers in CSRG constitute their UNIX system -BSD UNIX (Berkeley Software Distribution), released outward. BSD UNIX has considerable influence in the historical development of UNIX, which is adopted by many commercial manufacturers, and has become a lot of commercial UNIX, and the impact of AT & T's UNIX version is much smaller. At the same time, many research projects are also based on BSD UNIX for research systems, such as US Department of Defense, Aarpanet, ARPANET developed today into the Internet, and TCP / IP in BSD UNIX, which enables Internet and UNIX to closely combine.
And AT & T's UNIX system laboratory is also constantly improving their commercial UNIX version until they absorb all kinds of advanced features in BSD UNIX, and combined with their own characteristics, the Unix System V version is launched, Only change. Since then, BSD UNIX and UNIX SYSTEM V form two mainstreams of UNIX, and most of the modern Unix version is the two versions of derivatives. The version number of UNIX is complicated. Various Unix versions have their own version identity, such as the earliest AT & T developed internal UNIX to identify the version, from V 1 to V 7. BSD uses the main version to add the version of the method identifier, such as 4.2BSD, 4.3BSD, derived version on the basis of the original version, these versions usually have their own name, such as 4.3BSD-Net / 1,4.3BSD-NET / 2. AT & T uses Rome numbers to identify their foreign release UNIX version, with Release to represent a subset. For example, System V Release 4 identifies the fourth release of the Unix System V of AT & T of Unix System V. Other commercial companies' UNIX uses their own version identity, such as SUN Solaris 2.6, IBM AIX 4.0, etc. Although AT & T's UNIX System V is also very excellent UNIX version, BSD UNIX has a greater impact in UNIX. AT & T 's UNIX System Lab has been focused on the development of BSD. In 1992, UNIX system laboratory accused BSDI - a company that issued a commercial BSD UNIX company, violating AT & T's permissions, posted your own UNIX version, and further accused Berkeley Computer System Research Group leaked UNIX's commercial confidentiality (at this point in 4.3BSD from AT & T UNIX code is less than 10%). This lawsuit affected a lot of UNIX vendors, so they had to turn from BSD UNIX to UNIX System V to avoid legal issues. So most commercial UNIX versions today are based on UNIX System V. This case for UNIX copyright until UNIX system lab was sold to Novell by AT & T, Novell did not intend to fall into such legal disputes, so it used a relatively friendly approach. Berkeley's CSRG is allowed to freely release BSD, but the code from AT & T must be completely deleted. Therefore, CSRG has modified their latest 4.4BSD to delete source code from AT & T, released a 4.4 BSD Lite version (this system is incomplete, especially for computer systems for Intel 386). Since this version does not have legal issues, 4.4bsd Lite has become the foundation of the modern BSD system. Novell's relatively friendly approach not to BSD, he renamed his UNIX to Unixware, and gave the UNIX trademark to the Union of the Unix manufacturers, so that all members in this alliance can be used. UNIX trademark. Since then, UNIX is no longer a proprietary product. Later, Novell sold UnixWare to SCO due to their own business problems. At the same time, since the BSD system has been very mature, the goal of research on the operating system has been achieved, the Berkeley Computer System Research Group (CSRG) is dissolved after 4.4bsd-lite2, and the team's researchers have entered UNIX business. Companies, some continue to study other computer sectors.
At this point, Unix System v and BSD UNIX in strict sense have no longer exist, existed is just their various subsequent versions. Review UNIX's development, you can notice that UNIX is different from other commercial operating systems to its openness. The needs of various users are considered when the system starts design, so UNIX is designed to have a large scalable system. Since its source code is distributed to the university, there is a great impact in the education community and academic circles, which in turn affects the business sector. College students and researchers conduct a variety of development on UNIX for scientific research purposes or individual interest, and they are not allowed to disclose these source code, sharing each other, which greatly enriches Unix itself. Many scientists and technicians in computer areas have developed thousands of free software, including FreeBSD. Because of this, today's Internet is so rich, and it is different from other commercial networks to become a real global network. Open is the soul of UNIX and the soul of the Internet. Due to the openness of UNIX, there is a number of different UNIX versions on the other hand. Since different UNIX uses a slightly different file, a directory structure, providing a slightly different system calls, there is a certain difficulty for system management, and developing portable applications developing portable applications for UNIX. Many system calls such as System V and BSD are different. There is also a fully uniform effort in UNIX, such as the POSIX specification is a set of basic system calls that are negotiated by each UNIX manufacturer. However, due to the existence of multiple UNIX systems, the opinions of each manufacturer are very unfile, so the POSIX specification is very loose, and there is even a POSIX subsystem in Windows NT. In fact, as long as there is a coordinated development between the various UNIXs, it is not intentionally for commercial purposes, and it is possible to maintain the difference between the various UNIXs, and maintain the diversity of UNIX systems than only a unique UNIX system. More able to promote advancement and development of technology, attempted people's unified unix ideas can only be a unix manufacturer's wish. Sometimes, in order to avoid legal disputes, it shows that your program code is completely rewritten, and a software vendor deliberately declares some of the other functions of the other system, such as the order of different function parameters or change the function parameters. . Many system calls in UNIX System V are hereby here. These differences have caused the difference in source procedures for different systems. FreeBSD's origin and development of UNIX is not only the power of its functions, but also its excellent scalability, which provides advanced language C and various interpretation languages available for writing programs. With the tools provided by these systems, users can expand their original systems in their own needs and meet the needs of considerable computer researchers and users, so UNIX has more powerful capabilities to complete a variety of complexities. task. Once the Unix is used, it will experience the powerful function of UNIX, the user wants to use it all the time, not only other computer systems with limited capabilities. Enterprises also hopes to use the powerful processing capabilities of UNIX systems under the conditions they can withstand. Since UNIX is a multi-user operating system, the general user of the system can only use the limited functionality provided, and only UNIX system administrators can make full use of all its capabilities. Therefore, it is also a desire to have a general unix user. But at those time, the computer that meets these desires is not everyone can afford. Expensive hardware, and UNIX gradually commercial trend, making your own UNIX is just a good wish to most people, while using UNIX is mainly a high scientific research and large and medium-sized company agencies.
By the 1980s, the emergence of a personal computer made the price of hardware can be accepted by individuals and small businesses, bringing a first-line dawn to a wishes with a UNIX system. However, the personal computer capacity using the 8086 chip is relatively poor, and the multi-user system that is really working is not enabled. After entering the 1990s, Intel's 80386 chip has greatly improved the computing capacity of the personal computer, and building a Unix that can truly use on a personal computer has also become possible. In fact, Unix can run on the X86 platform is quite limited, and Mircosoft's xienx is a kind of (later developed into sco unix), but it is not expected to be free, free to use this commercial system. To port UNIX to the PC platform, you need UNIX source code, which is limited by AT & T's permissions, and UNIX code cannot be freely obtained (but 4.4 BSD Lite after the BSD and AT & T's legal disputes is no longer this Limited, it can be freely used under the BSD license). Many computer enthusiasts do not only work hard to achieve a freely used operating system. The purpose of the GNU program of the Free Software Foundation is to intend to create a free, similar to UNIX, in order to achieve this, GNU has developed a lot of very effective tools, including compilers and many system commands, but GNU plans Operating system kernel - Hurd, slow progress, and unable to build a complete operating system. Soon, computer enthusiasts have begun to consider building a UNIX kernel on a personal computer platform. Finland a computer graduate LINUS Torvalds started this, he built a Linux kernel on the X86 platform by learning Minix - a simple UNIX system for teaching purposes, and built a Linux kernel on the X86 platform. This kernel and GNU system tools combine it. Big success is a very popular GNU / Linux system. Compared with these efforts, the Action of BSD researchers is relatively slow. One reason is that UNIX technology is quite mature, most members of the computer system research group have turned their attention to other research projects, additional AT & T and BSD Legal disputes have also hindered BSD development. But there are still two development work that transplant BSD to 80386 platforms, one is the BSD / 386 group, and their findings are commercial versions of BSD / OS, belonging to commercial companies BSDI. The other is a 386BSD program, which is later developed into freebsd. The CSRG researchers have a superior condition, with enough UNIX systems, so the UNIX system on the personal computer platform is not too eager to require. 386BSD plans to be initiated by researchers such as Bill Jolitz, port 4.3BSD NET / 2 to the 80386 platform, and published using 386BSD names. However, the graft work is a complex task until the 386BSD version 0.5 version, there is still a considerable issue in the system that there is no solution. So in 1993, other researchers decided to join this plan, intend to correct the problems existing in the system together with Bill Jolitz. But at this time, the organizer Bill Jolitz suddenly decided to exit, making the 386BSD plan to stop the danger. Bill Jolitz as a planned initiator and the person in charge did not give specific advice after the plan, so the 386BSD program continued to develop, depending on other developers' decisions.
Fortunately, the other three participants of the project Nate Williams, Rod Grimes, and Jordan K. Hubbard decided to continue this very meaningful job, they used the name freebsd created by David Green Man as a new name of the system, from now on A UNIX operating system that is free to use - FreeBSD. BSD UNIX uses a myth's elf as its mascot, this mascot mark is continued by FreeBSD, but NetBSD, but the elves of different BSD systems are slightly different, and the picture is the BSD wizard of FreeBSD. When a user browses the Internet, this cute wizard sign is seen on a lot of website related to FreeBSD.
In December 1993, it is very important for FreeBSD, and the FreeBSD version 1.0 is officially released this month. This freeBSD developer finds a publisher Walnet Creek to support freebsd disc and provide high-speed Internet network services, so that anyone can freely obtain the FreeBSD system by purchasing a CD or through the Internet Download, make FreeBSD It has achieved great success. Walnet Creek also used FreeBSD to built the largest, busiest anonymous file server on the Internet - FTP.cdrom.com. Although FreeBSD can be freely obtained, BSD and AT & T legal disputes still threaten the legality of the FreeBSD system. When FreeBSD was very popular, the UNIX system laboratory (at this time, it has been sold to Novell) has conclusions with the legal disputes of the Berkeley Computer System Research Group. Although it is not necessary to compensate, the source code from AT & T must be removed in the BSD UNIX system. Berkeley Computer System Research Group removes these less than 10% source code, released 4.4BSD Lite, other BSD-based UNIX, including FreeBSD, is required to be converted to 4.4 BSD LITE. This is a quite serious blow to FreeBSD, although 4.4 BSD Lite only deletes a small piece of code, but especially for Intel 80386 platform, the system lacks these code, the system cannot work properly. The FreeBSD team must solve two tasks, first to migrate FreeBS D from the original 4.3BSD to 4.4BSD, and then rewrite the deleted source code. These tasks are equivalent to re-transplanting 4.4bsd lite on 80386, so this costs a lot of effort. So until January 1995 they released FreeBSD 2.0, this time is a completely 4.4BSD Lite system. However, in about one year, FreeBSD cannot improve and introduce new versions on the original 1.0 basis, and this period is the stage of Internet further development, FreeBSD missed a well-developed good time. And its competitors, such as Linux, have achieved great success. Next, FreeBSD speeds up the development rhythm, 2.1, 2.2, 3.0 successively, this system is more and more applications on the Internet, especially for high performance, high-reliability network server systems, FreeBSD provides a pole Temptic choice. Since the UNIX trademark belongs to the X / Open organization, FreeBSD is just a free operating system, and FreeBSD cannot be called Unix from the legal perspective (not using UNIX). However, based on the history of UNIX itself, FreeBSD can be the most original Unix, in some aspects, it is more traditional - or says the BSD UNIX college characteristics. Currently, UNIX trademarks actually have symbolic meaning, no one minds those systems are members of X / Open, which can be called Unix, those are not. UNIX has become a broad concept, as long as it is developed in accordance with UNIX, all applications are compatible with other UNIXs and other UNIXs, and are also recognized by all users as UNIX systems. Therefore, Unix here includes various systems including BSD and System V, including compatible systems like Linux. The current version of FreeBSD is very concerned about the performance and stability of FreeBSD, while FreeBSD is very active and is very open.
Therefore, in system development, it supports multiple versions of FreeBSD systems in parallel, some versions are used to provide a most stable operating system, and others have gradually integrated into a new feature, so that FreeBSD is constantly evolving. The currently used FreeBSD has three branches: Freebsd2.2.x-stable: This branch is the FreeBSD version used on most network servers on the Internet, and has a high stability feature. However, since the 3.0 version has been officially released, FreeBSD's developers have decided to stop this version in January 1999. The branch version of this FreeBSD enters the maintenance state, which will only patch some of the possible system vulnerabilities. Therefore, unless an existing FreeBSD system, or for special purpose, some 2.2.x-developed special software should be used, the newly installed FreeBSD system should use the FreeBSD-3.x version. The last officially released disc version of this series is FreeBSD 2.2.8-Release. Freebsd3.x-stable: The first official version of this version 3.0-release, which was officially released in October 1998, and then became a stable version. It adds support for many new hardware compared to 2.2, and further improves performance. This version should be selected for installing a new FreeBSD system. FreeBSD 3.2-Release has been released. FreeBSD4.0-CURRENT: Generated in January 1999, and the FreeBSD 3.x-Current branch transitions to FreeBSD 3.x-Stable branch. There is currently no formal release, you need to get the source code through the Internet. It can be seen that freebsd is modified with a Current or Stable suffix, where using stable modified version is a stable version, it is not the latest version of FreeBSD, the main concern of the system, the continuity of the system, the same Stable branch The next version is mainly revised system issues, so the Stable branch is welcomed by many commercial users. Current means this version is a version being developed, is not mature, it is more concerned about new features, each possible feature is tried to join FreeBSD, but not guaranteed all feature, Some features will be inadvertent because they are not mature or to most users, even if they have been added or may be removed from official versions. Usually FreeBSD enthusiasts and developers use this branch, or some users who need some FreeBSD, you must use this branch. FreeBSD uses current and stable to modify FreeBSD is not only because FreeBSD is a system that is constantly developing, updated, and FreeBSD is also a system that is involved in users on the Internet, using Internet Exchange development. This is different from business software, and the development of commercial software is within the company, and the outside world cannot access the version being developed. It is not possible to make comments and proposals for software to develop. And freeBSD, anyone can access the source code of FreeBSD as long as you pass through the Internet, and FreeBSD developers encourage others to access the current source of origin, encourage suggestions and conduct their own FreeBSD development plan, if this plan is really good, Then this developer can be invited to enter the FreeBSD development group, and his plan can be merged into official FreeBSD development. However, if a system is always developing process, there is no stable version, which is clearly not conducive to the ordinary users who want to use FreeBSD to use the daily business handling task.
