> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/4.3-bsd-unix-cao-zuo-xi-tong-she-ji-yu-shi-xian/di-yi-bu-fen-gai-lan/2.13.-xi-tong-yun-xing.md).

# 2.13 系统运行

系统靠自举机制启动运行。首先，UNIX 内核必须装入处理器的主存。装入之后，内核要经过一个初始化阶段，把硬件设置到已知状态。接着，内核必须做自动配置——一个发现并配置接在处理器上的外设的过程。系统先以单用户方式开始运行，由一个启动脚本检查磁盘，并启动记账和配额检查。最后，启动脚本启动通用系统服务，把系统带入完整的多用户运行。

多用户运行期间，进程在为用户访问配置的终端线路和网络端口上等待登录请求。检测到登录请求时，产生一个登录进程并做用户验证。登录验证成功后，创建一个登录 shell，用户可以从它运行更多进程。

## 习题

2.1 用户进程如何向内核请求服务？

2.2 数据怎样在进程与内核之间传输？有哪些可选方案？

2.3 进程如何访问一个 I/O 流？列出三种 I/O 流。

2.4 进程生命周期的四个步骤是什么？

2.5 4.3BSD 为什么要提供进程组？

2.6 内核有哪些与机器相关的功能？

2.7 描述绝对路径名与相对路径名的区别。

2.8 在添加 `mkdir` 系统调用之前，在当前目录下创建一个新目录 **foo** 需要哪三个系统调用？给出 `mkdir` 系统调用加入 4.2BSD 的三条理由。

2.9 定义分散/聚集 I/O。它为什么有用？

2.10 块设备与字符设备有什么区别？

2.11 列出终端驱动提供的五种功能。

2.12 管道与套接字有什么区别？

2.13 描述如何创建管道线中的一组进程。

\*2.14 解释进程间通信与联网的区别。

## 参考文献

Accetta et al., 1986. M. Accetta, R. Baron, D. Golub, R. Rashid, A. Tevanian, & M. Young, “Mach: A New Kernel Foundation for UNIX Development,” Technical Report, Carnegie Mellon University, Pittsburgh, PA (August 1986).

Cheriton, 1988. D. R. Cheriton, “The V Distributed System,” *Comm ACM* **31**(3), pp. 314–333 (March 1988).

Ewens et al., 1985. P. Ewens, D. R. Blythe, M. Funkenhauser, & R. C. Holt, “Tunis: A Distributed Multiprocessor Operating System,” *USENIX Association Conference Proceedings*, pp. 247–254 (June 1985).

Fitzgerald & Rashid, 1986. R. Fitzgerald & R. F. Rashid, “The Integration of Virtual Memory Management and Interprocess Communication in Accent,” *ACM Transactions on Computer Systems* **4**(2), pp. 147–177 (May 1986).

Gingell et al., 1987. R. A. Gingell, J. P. Moran, & W. A. Shannon, “Virtual Memory Architecture in SunOS,” *USENIX Association Conference Proceedings*, pp. 81–94 (June 1987).

Joy et al., 1986. W. N. Joy, R. S. Fabry, S. J. Leffler, M. K. McKusick, & M. J. Karels, “Berkeley Software Architecture Manual, 4.3BSD Edition,” pp. 6:1–43 in *UNIX Programmer's Supplementary Documents, Volume I, 4.3 Berkeley Software Distribution, Virtual VAX-11 Version*, USENIX Association, Berkeley, CA (1986).

Kernighan & Pike, 1984. B. W. Kernighan & R. Pike, *The UNIX Programming Environment*, Prentice-Hall, Englewood Cliffs, NJ (1984).

McKusick et al., 1985. M. K. McKusick, M. Karels, & S. Leffler, “Performance Improvements and Functional Enhancements in 4.3BSD,” *USENIX Association Conference Proceedings*, pp. 519–531 (June 1985).

McKusick & Karels, 1988. M. K. McKusick & M. J. Karels, “Design of a General Purpose Memory Allocator for the 4.3BSD UNIX Kernel,” *USENIX Association Conference Proceedings*, pp. 295–304 (June 1988).

Ritchie, 1988. D. M. Ritchie, “Early Kernel Design,” private communication (March 1988).


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