0201549794.Addison-Wesley Professional.The Design and Implementation of the 4.4 BSD ...

326 Pages·2005·22.05 MB·English

Contents
Part 1 Overview
1
Chapter 1 History and Goals 3
1.1 History of the UNIX System 3
Origins 3
Research UNIX 4
AT&T UNIX System III and System V
Other Organizations 8
Berkeley Software Distributions 8
UNIX in the World 10
1.2 BSD and Other Systems 10
The Influence of the User Community 11
1.3 Design Goals of 4BSD 12
4.2BSD Design Goals 13
4.3BSD Design Goals 14
4.4BSD Design Goals 15
1.4 Release Engineering 16
References 17
Chapter 2 Design Overview of 4.4BSD 21
2.1 4.4BSD Facilities and the Kernel 21
The Kernel 22
2.2 Kernel Organization 23
2.3 Kernel Services 25
2.4 Process Management 26
Signals 27
Process Groups and Sessions 28
2.5 Memory Management 29
BSD Memory-Management Design Decisions 29
xvii
Resource Limits 70
13 lenreK eht edisnI tnemeganaM yromeM
Filesystem Quotas 70
2.6 I/O System 31 3.9 System-Operation Services 71
Descriptors and I/O 32
Accounting 71
Descriptor Management 33
Exercises 72
Devices 34
References 73
Socket IPC 35
Scatter/Gather I/O 35
Multiple Filesystem Support 36
75
2.7 Filesystems 36 Part 2 Processes
2.8 Filestores 40
2.9 Network Filesystem 41 tnemeganaM ssecorP 4 retpahC 77
2.10 Terminals 42
4. 1 Introduction to Process Management 77
2.11 Interprocess Communication 43
Multiprogramming 78
2.12 Network Communication 44
Scheduling 79
2.13 Network Implementation 44
08 etatS ss4e.c2orP
54 noitarepO metsyS 41.2
The Process Structure 8 1
Exercises 45
58 erutcurtS resU ehT
References 46
78 gnihctiwS txetno4.3C
78 etatS ssecorP
Chapter 3 Kernel Services 49 Low-Level Context Switching 88
94 noitazinagrO lenreK 1.3 Voluntary Context Switching 88
Synchronization 91
System Processes 49
05 yrtnE metsyS 4.4 Process Scheduling 92
05 noitazinagrO emiT-nuR Calculations of Process Priority 93
25 lenreK eht ot yrtnE Process-Priority Routines 95
96
Process Run Queues and Context Switching
Return from the Kernel 53
3.2 System Calls 53 4.5 Process Creation 98
Result Handling 54 4.6 Process Termination 99
45 llaC metsyS a morf gninruteR 4.7 Signals 100
3.3 Traps and Interrupts 55 Comparison with POSIX Signals 103
Traps 55 401 langiS a fo gnitsoP
55 stpurretnI eciveD O/I 601 langiS a gnirevileD
Software Interrupts 56 snoisseS dna spuorG4 .ss8ecorP 107
75 stpurretnI kcolC 4.3 Sessions 109
85 gniludehcS ssecorP dna scitsitatS Job Control 110
Timeouts 58 4.9 Process Debugging 112
06 secivreS tnemeganaM-yromeM 5.3 Exercises 114
36 secivreS gnimiT 6.3 References 116
Real Time 63
117
Adjustment of the Time 63 tnemeganaM yromeM 5 retpahC
External Representation 64
5.1 Terminology 117
46 emiT lavretnI
Processes and Memory 118
56 sreifitnedI rehtO dna ,puorG ,resU 7.3
Paging 119
Host Identifiers 67
Replacement Algorithms 120
Process Groups and Sessions 68
Working-Set Model 121
3.8 Resource Services 68
Swapping 121
Process Priorities 69 Advantages of Virtual Memory 122
Resource Utilization 69
Hardware Requirements for Virtual Memory 122
5.2 Overview of the 4.4BSD Virtual-Memory System 123
191
621 tnemeganaM yromeM lenr5e.3K
Part 3 I/O System
Kernel Maps and Submaps 127
193
Kernel Address-Space Allocation 128 Chapter 6 I/O System Overview
Kernel Malloc 129
193
231 secruoseR ssecorP-reP5.4 eciveD ot resU morf gnippaM O/I 1.6
ecapS sserddA-lautriV ssecorP DSB4.4 132 Device Drivers 195
Page-Fault Dispatch 134 I/O Queueing 195
Mapping to Objects 134 Interrupt Handling 196
Objects 136 691 seciveD kc6o.2lB
731 segaP ot stcejbO Entry Points for Block-Device Drivers 197
5.5 Shared Memory 137 891 stseuqeR O/I ksiD fo gnitroS
Mmap Model 139 991 slebaL ksiD
Shared Mapping 141 002 seciveD re6tc.a3rahC
Private Mapping 142 102 O/I lacisyhP dna seciveD waR
Collapsing of Shadow Chains 144 202 seciveD detneirO-retcarahC
203
541 stohspanS etavirP Entry Points for Character-Device Drivers
ssecorP weN a fo noi5ta.6erC 146 6.4 Descriptor Management and Services 205
Reserving Kernel Resources 147 Open File Entries 205
Duplication of the User Address Space 148 Management of Descriptors 207
Creation of a New Process Without Copying 149 File-Descriptor Locking 209
5.7 Execution of a File 150 Multiplexing I/O on Descriptors 211
ecapS sserddA stI fo noitalupinaM ssec5o.8rP 151 Implementation of Select 213 216
lenreK eht edisnI ataD fo tnemevoM
Change of Process Size 151
File Mapping 152 6.5 The Virtual-Filesystem Interface 218
451 noitcetorP fo egnahC 912 edonV a fo stnetnoC
5.9 Termination of a Process 154 Vnode Operations 220
Pathname Translation 222
5.10 The Pager Interface 156
Exported Filesystem Services 222
Vnode Pager 157
951 regaP eciveD 6.6 Filesystem-Independent Services 223
The Name Cache 225
061 regaP pawS
Buffer Management 226
5.11 Paging 162
Implementation of Buffer Management 229
5.12 Page Replacement 166
6.7 Stackable Filesystems 231
Paging Parameters 168
432 sreyaL metsyseliF elpmiS
The Pageout Daemon 169
The Union Mount Filesystem 235
Swapping 171
732 smetsyseliF rehtO
The Swap-In Process 172
Exercises 238
5.13 Portability 173
References 240
eludoM pamp eht fo eloR ehT 176
Initialization and Startup 179 241
Chapter 7 Local Filesystems
181 noitacollaeD dna noitacollA gnippaM
241
Change of Access and Wiring Attributes for Mappings 184 tnemeganaM metsyseliF lacihcrareiH 1.7
Management of Page-Usage Information 185 342 edonI na fo erutcurtS 2.7
681 segaP lacisyhP fo noitazilaitinI Inode Management 245
681 serutcurtS ataD lanretnI fo tnemeganaM 7.3 Naming 247
Exercises 187 Directories 247
References 188 Finding of Names in Directories 249
Pathname Translation 249 223 seussI tropsnarT CPR
Links 251 Security Issues 324
7.4 Quotas 253 9.3 Techniques for Improving Performance 325
7.5 File Locking 257 Leases 328
262 scitnameS metsyseliF rehtO 6.7 Crash Recovery 332
262 seziS eliF egraL Exercises 333
362 sgalF eliF References 334
Exercises 264 337
Chapter 10 Terminal Handling
References 264
10.1 Terminal-Processing Modes 338
Chapter 8 Local Filestores 265 933 senilpicsiD10 e.2niL
8.1 Overview of the Filestore 265 10.3 User Interface 340
8.2 The Berkeley Fast Filesystem 269 10.4 The tty Structure 342
Process Groups, Sessions, and Terminal Control 343
Organization of the Berkeley Fast Filesystem 269 10.5
172 noitazilitU egarotS fo noitazimitpO 10.6 C-lists 344
Reading and Writing6 to4 a F3ile 273 lortnoC medoM dna 232-S10.R7
Filesystem Parameterization 275 10.8 Terminal Operations 347
Layout Policies 276 Open 347
Allocation Mechanisms 277 743 enilpicsiD eniL tuptuO
182 gniretsulC kcolB 943 flaH poT tuptuO
Synchronous Operations 284 Output Bottom Half 350
582 metsyseliF derutcurtS-goL ehT 3.8 153 flaH mottoB tupnI
Organization of the Log-Structured Filesystem 286 253 flaH poT tupnI
882 eliF xednI The stop Routine 353
Reading of the Log 290 The ioctl Routine 353
Writing to the Log 291 Modem Transitions 354
Block Accounting 292 Closing of Terminal Devices 355
The Buffer Cache 294 553 senilpicsiD eniL 1r0e.h9tO
snoitarepO yrotceriD 295 653 enilpicsiD PI eniL laireS
Creation of a File 296 Graphics Tablet Discipline 356
792 eliF a ot gnitirW dna gnidaeR Exercises 357
Filesystem Cleaning 297 References 357
Filesystem Parameterization 300
Filesystem-Crash Recovery 300
359
8.4 The Memory-Based Filesystem 302 Part 4 Interprocess Communication
metsyseliF desaB-yromeM eht fo noitazinagrO 303
361
Filesystem Performance 305 noitacinummoC ssecorpretnI 11 retpahC
503 kroW erutuF
11.1 Interprocess-Communication Model
Exercises 306
Use of Sockets 364
References 307 weivrevO dna erutcurtS noitatnemelpmI 2.11 368
963 tnemeganaM yromeM 3.11
Chapter 9 The Network Filesystem 311
Mbufs 369
9.1 History and Overview 311 Storage-Management Algorithms 372
9.2 NFS Structure and Operation 314 Mbuf Utility Routines 373
The NFS Protocol 316 473 serutcurtS ataD 4.11
The 4.4BSD NFS Implementation 318 Communication Domains 375
Client-Server Interactions 321 Sockets 376
Socket Addresses 378
slocotorP krowteN 31 retpahC 435
11.5 Connection Setup 380
11.6 Data Transfer 382 13.1 Internet Network Protocols 436
383 ataD gnittimsnarT 734 sesserddA tenretnI
Receiving Data 385 Subnets 438
Passing Access Rights 388 Broadcast Addresses 441
Passing Access Rights in the Local Domain 389 Internet Multicast 441
11.7 Socket Shutdown 390 244 snoitaicossA dna stroP tenretnI
Exercises 391 Protocol Control Blocks 442
References 393 13.2 User Datagram Protocol (UDP) 443
Initialization 443
Chapter 12 Network Communication 395 Output 444
Input 445
12.1 Internal Structure 396
Control Operations 446
Data Flow 397
644 )PI( locotorP tenretnI 3.31
893 slocotorP noitacinummoC
Output 447
Network Interfaces 400
Input 448
504 ecafretnI loco1to2rP-.o2t-tekcoS
Forwarding 449
Protocol User-Request Routine 405
154 )PCT( locotorP lortnoC noissimsnarT 4.31
904 stseuqeR lanretnI
354 setatS noitcennoC PCT
904 enituoR tuptuO-lortnoC locotorP
654 selbairaV ecneuqeS
014 ecafretnI locotorP-1lo2c.o3torP
13.5 TCP Algorithms 457
pr_output 411
Timers 459
pr_input 411
Estimation of Round-Trip Time 460
pr_ctlinput 411
164 tnemhsilbatsE noitcennoC
12.4 Interface between Protocol and Network Interface 412
Connection Shutdown 463
Packet Transmission 412
464 gnissecorP tupnI PCT 6.31
Packet Reception 413
13.7 TCP Output Processing 468
12.5 Routing 416
Sending of Data 468
Kernel Routing Tables 417
964 emordnyS wodniW-ylliS eht fo ecnadiovA
024 pukooL gnituoR
Avoidance of Small Packets 470
Routing Redirects 423
174 setadpU wodniW dna stnemgdelwonkcA deyaleD
Routing-Table Interface 424
Retransmit State 472
User-Level Routing Policies 425
Slow Start 472
User-Level Routing Interface: Routing Socket 425
Source-Quench Processing 474
12.6 Buffering and Congestion Control 426
Buffer and Window Sizing 474
Protocol Buffering Policies 427
574 tratS wolS htiw noitsegnoC fo ecnadiovA
724 gnitimiL eueuQ
Fast Retransmission 476
12.7 Raw Sockets 428
774 )PMCI( locotorP egasseM lortnoC tenretnI 8.31
Control Blocks 428
13.9 OSI Implementation Issues 478
Input Processing 429
noitacinummoC ssecorpretnI dna gnikrowteN fo yrammuS 01.31 480
Output Processing 429
Creation of a Communication Channel 481
12.8 Additional Network-Subsystem Topics 429
284 ataD fo gnivieceR dna gnidneS
Out-of-Band Data 430
Termination of Data Transmission or Reception 483
034 locotorP noituloseR sserddA
Exercises 484
Exercises 432
References 486
References 433
PART1
noitarepO metsyS 5 traP 489
Chapter 14 System Startup 491
Overview
14.1 Overview 491
14.2 Bootstrapping 492
The boot Program 492
14.3 Kernel Initialization 493
Assembly-Language Startup 494
594 noitazilaitinI tnednepeD-enihcaM
Message Buffer 495
System Data Structures 496
14.4 Autoconfiguration 496
894 gniborP eciveD
994 tnemhcattA eciveD
994 serutcurtS ataD noitarugifnocotuA weN
105 snoitcnuF noitarugifnocotuA weN
Device Naming 501
14.5 Machine-Independent Initialization 502
505 noitazilaitinI leveL-resU 6.41
/sbin/init 505
/etc/re 505
/usr/libexec/getty 506
/usr/bin/login 506
14.7 System-Startup Topics 507
705 noitarugifnoC lenreK
705 tooberotuA dna nwodtuhS metsyS
System Debugging 508
lenreK eht morF dna oT noitamrofnI fo egassaP 509
Exercises 511
References 511
Glossary 513
Index 551
CHAPTER
History and Goals
1.1 History of the UNIX System
The UNIX system has been in wide use for over 20 years, and has helped to define
detubirtnoc evah snoitazinagro suoremun hguohtlA .gnitupmoc fo saera ynam
(and still contribute) to the development of the UNIX system, this book will pri-
marily concentrate on the BSD thread of development:
XINU detnevni hcihw ,seirotarobaL lleB •
ainrofilaC fo ytisrevinU eht ta )GRSC( puorG hcraeseR smetsyS retupmoC ehT •
at Berkeley, which gave UNIX virtual memory and the reference implementation
of TCP/IP
• Berkeley Software Design, Incorporated (BSDI), The FreeBSD Project, and The
GRSC eht yb detrats krow eht eunitnoc hcihw ,tcejorP DSBteN
Origins
9691 ni seirotarobaL lleB ta depoleved saw metsys XINU eht fo noisrev tsrif ehT
by Ken Thompson as a private research project to use an otherwise idle PDP-7.
-noc ylno ton ohw ,eihctiR sinneD yb retfaereht yltrohs denioj saw nospmohT
tributed to the design and implementation of the system, but also invented the C
gnivael ,C otni nettirwer yletelpmoc saw metsys ehT .egaugnal gnimmargorp
,eihctiR[ metsys eht fo ngised tnagele lanigiro ehT .egaugnal ylbmessa on tsomla
]5891 ,notpmoC ;a4891 ,eihctiR[ sraey 51 tsap eht fo stnempoleved dna ]8791
have made the UNIX system an important and powerful operating system [Ritchie,
1987].
dah seirotarobaL lleB ta srepoleved XINU ylrae rehto dna ,nospmohT ,eihctiR
worked previously on the Multics project [Peirce, 1985; Organick, 1975], which
had a strong influence on the newer operating system. Even the name UNIX is
USG/USDUATTIS Bell Laboratories Berkeley Software
merely a pun on Multics; in areas where Multics attempted to do many tasks, DSG/USO/USL Research Distributions
eht ,metsyselif XINU eht fo noitazinagro cisab ehT .llew ksat eno od ot deirt XINU noitidE tsriF
1969
noitazinagro lareneg eht ,reterpretni dnammoc eht rof ssecorp resu a gnisu fo aedi
of the filesystem interface, and many other system characteristics, come directly
from Multics. noitidE htfiF
1973
-itsnI sttesuhcassaM eht sa hcus ,smetsys gnitarepo rehto suoirav morf saedI
tute of Technology's (MIT's) CTSS, also have been incorporated. The ofrk opera-
retal ,049-SDS( EINEG s'yelekreB morf semoc sessecorp wen etaerc ot noit Sixth Edition
1976
XDS-940) operating system. Allowing a user to create processes inexpensively led
-ecorp sa nur gnieb sdnammoc ot naht rehtar ,dnammoc rep ssecorp eno gnisu ot
dure calls, as is done in Multics. 1BSD
1977 PWB MERT CB UNIX
.metsys XINU eht fo tnempoleved fo smaerts rojam eerht tsael ta era erehT
Figure 1.1 sketches their early evolution; Figure 1.2 (shown on page 6) sketches
DSB4.4 ot gnidael sehcnarb esoht rof yllaicepse ,stnempoleved tnecer erom rieht 2BSD
1978
setad ehT .]5891 ,ikswejeinU ;3891 ,namretrauQ & srebmahC[ V metsyS ot dna
.secneulfni lla wohs ot tpmetta on edam evah ew dna ,etamixorppa era nevig
era tub ,txet eht ni denoitnem ton era erugif eht ni deman smetsys eht fo emoS
included to show more clearly the relations among the ones that we shall examine.
Research UNIX
1979
-otarobaL lleB morf smetsys hcraeseR eht erew XINU fo snoitide rojam tsrif ehT
ries. In addition to the earliest versions of the system, these systems include the
ni ,hcihw ,6V sa nwonk ylnommoc ,noitidE htxiS ,metsyS gnirahS-emiT XINU
1976, was the first version widely available outside of Bell Laboratories. Systems
e ra identifiede ht yb edition numberse ht fo UNIX Programmer's Manual that were 1980
3.0.1
current when the distributions were made.
The UNIX system was distinguished from other operating systems in three
important ways: 1981 4.0.1
1. The UNIX system was written in a high-level language.
.mrof ecruos ni detubirtsid saw metsys XINU ehT .2 1982 5.0 System III
2.8BSD
3. The UNIX system provided powerful primitives normally found in only those
operating systems that ran on much more expensive hardware.
1983 5.2 SystemV XENIX 3 Eighth 4.1cBSD
Edition
Most of the system source code was written in C, rather than in assembly lan-
eb ot dah metsys gnitarepo na taht saw emit eht ta feileb gniliaverp ehT .egaug
written in assembly language to provide reasonable efficiency and to get access to 2.9BSD
ot ti wolla ot level hgih yltneiciffus a ta saw flesti egaugnal C ehT .erawdrah eht
SOnuS VmetsyS 4891 4.2BSD
be compiled easily for a wide range of computer hardware, without its being so Release 2
complex or restrictive that systems programmers had to revert to assembly lan-
guage to get reasonable efficiency or functionality. Access to the hardware was
1985
-sys-gnitarepo eht fo tnecrep 3 eht rof sbuts egaugnal-ylbmessa hguorht dedivorp
-cus eht hguohtlA .meht dedeen taht—gnihctiws txetnoc sa hcus—snoitcnuf met .5891-9691 ,eert ylimaf metsys XINU ehT 1.1 erugiF
cess of UNIX does not stem solely from its being written in a high-level
System V Eighth language, the use of C was a critical first step [Ritchie et al, 1978; Kernighan &
1985 Release 2 DSB9.X2 EDSNB2I.4X 3 noitidE SOnuS
dednecsed si egaugnal C s'eihctiR .]8891 ,eihctiR & nahginreK ;8791 ,eihctiR
[Rosier, 1984] from Thompson's B language, which was itself descended from
1986 ;5891 ,llihtuT[ evlove ot seunitnoc C .]0891 ,snevertS-ybtihW & sdrahciR[ LPCB
X3J11, 1988], and there is a variant—C++—that more readily permits data
.]7891 ,XINESU ;4891 ,purtsuortS[ noitcartsba
-baL lleB morf esaeler ylrae sti saw XINU fo noitcnitsid tnatropmi dnoces ehT
oratories to other research environments in source form. By providing source, the
1987Chorus 2.10BSD esu ot ylno ton elba eb dluow snoitazinagro rehto taht derusne srednuof s'metsys
wen hcihw htiw esae ehT .sgnikrow renni sti htiw reknit ot osla tub ,metsys eht
taht segnahc eht ot yek neeb sah syawla metsys eht otni detpoda eb dluoc saedi
emac XINU egatspu ot deirt taht metsys wen a revenehW .ti ot edam neeb evah
1988 along, somebody would dissect the newcomer and clone its central ideas into
UNIX. The unique ability to use a small, comprehensible system, written in a
-sys XINU a ot del saedi wen ni gnimmiws tnemnorivne na ni ,egaugnal level-hgih
tem that evolved far beyond its humble beginnings.
sresu laudividni dedivorp ti taht saw XINU fo noitcnitsid tnatropmi driht ehT
1989
2.11BSD with the ability to run multiple processes concurrently and to connect these pro-
gninnur smetsys gnitarepo ylno ,emit eht tA .sdnammoc fo senilepip otni sessec
Chorus
V3 eht dna ,sessecorp elpitlum nur ot ytiliba eht dah senihcam evisnepxe dna egral no
number of concurrent processes usually was controlled tightly by a system admin-
1990 istrator.
dna evisnepxeni saw hcihw ,11-PDP eht no nar smetsys XINU ylrae tsoM
powerful for its time. Nonetheless, there was at least one early port of Sixth Edi-
,relliM[ 23/7 1a9t9a1dretnI eht ,erutcetihcra tnereffid a htiw enihcam a ot XINU noit
-cudortni ehT .ecaps sserdda llams yltneinevnocni na dah osla 11-PDP ehT .]8791
tion of machines with 32-bit address spaces, especially the VAX-11/780, provided
-ten dna 1y9r9o2mem lautriv edulcni ot secivres sti dnapxe ot XINU rof ytinutroppo na
-licaf ekil-XINU gnidivorp ni puorg hcraeseR eht yb stnemirepxe reilraE .gnikrow
evom ot ysae sa saw ti taht noisulcnoc eht ot del dah erawdrah tnereffid no seiti
rehtona rednu secivres s'XINU etacilpud ot saw ti sa metsys gnitarepo eritne eht
BSDI 1.0
Novell operating system. The first UNIX system with portability as a specific goal was
XINU xuniL 3991 11-PDP eht no nar hcihw ,)7V( noitidE htneveS ,metsyS gnirahS-emiT XINU
Ware
and the Interdata 8/32, and had a VAX variety called UNIX/32V Time-Sharing,
System Version 1.0 (32V). The Research group at Bell Laboratories has also
1994
developed UNIX Time-Sharing System, Eighth Edition (V8), UNIX Time-Shar-
ing System, Ninth Edition (V9), and UNIX Time-Sharing System, Tenth Edi-
.9 nalP si metsys 6991 riehT .)01V( noit
1995
4.4BSD BSDI2.°
AT&T UNIX System III and System V
1996 revo denrut puorg hcraeseR eht ,8791 ni noitidE htneveS fo noitubirtsid eht retfA
external distributions to the UNIX Support Group (USG). USG had previously dis-
Figure 1.2 The UNIX system family tree, 1986-1996. ,)BWP( hcneB kroW s'remmargorP XINU eht sa smetsys hcus yllanretni detubirt
.]5891 ,rhoM[ llew sa yllanretxe meht detubirtsid semitemos dah dna
USG's first external distribution after Seventh Edition was UNIX System III fo tnempoleved eht saw DSB3 fo ecaps yromem-lautriv egral eht rof nosaer ehT
-mem sihT .PSIL znar(SFys tesm'y IeIIl),e ikn r1e98B2, wshaic hh icncuorspo r,astemd faeartugreos ropf Seevgenrtah lE deitiroen,w of e32mV,it eht ta tahw
and also of several UNIX systems developed by groups other than the ReseastcrejcorPh hcraeseR decnavdA esnefeD eht decnivnoc krow tnemeganam-yro
group. Features of UNIX /RT (a real-time UNIX system) were included, as were Agency (DARPA) to fund the Berkeley team for the later development of a stan-
many features from PWB. USG released UNIX System V (System V) in 1983; .esu ot srotcartnoc s'APRAD rof )DSB4( metsys drad
fo erutitsevid deredro-truoc ehT .III metsyS morf devired ylegral si metsys taht A goal of the 4BSD project was to provide support for the DARPA Internet
the Bell Operating Companies from AT&T permitted AT&T to market System V networking protocols, TCP/IP [Cerf & Cain, 1983]. The networking implementa-
aggressively [Wilson, 1985; Bach, 1986]. -gnar ,seitilicaf krowten esrevid gnoma etacinummoc ot hguone lareneg saw noit
,)LDSU( yrotarobaL tnempoleveD metsyS XINU eht otni desohpromatem GSU ,skrowten luah-gnol ot ,sgnir nekot dna stenrehtE sa hcus ,skrowten lacol morf gni
-reV ,2 esaeleR ,V metsyS .4891 ni 2 esaeleR ,V metsyS XINU desaeler hcihw .TENAPRA s'APRAD sa hcus
sion 4 introduced paging [Miller, 1984; Jung, 1985], including copy-,DoSnB4-w sa rDiStBe3 ganniwdollof smetsys XINU XAV yelekreB eht lla ot refer eW
shared memory, to System V The System V implementation was not based on the although there were really several releases—4.0BSD, 4.1BSD, 4.2BSD, 4.3BSD,
smetsyS noitamrofnI T&TA yb dedeeccus saw LDSU .metsys gnigap yelekreB 4.3BSD Tahoe, and 4.3BSD Reno. 4BSD was the UNIX operating system of choice
(ATTIS), ewhth ilciht nduis t7ri7b9u1ted n iU NelIbXa liSayvsate mem Va, cRebel etassrei f3 XinA V198 e7h. t Ttahhatt seymstietm eht morf seXAV rof
,eihctiR & ottoserP[ 8V morf detpoda msinahcem CPI na ,SMAERTS dedulcni ,esnecil V23 a esahcrup dluow snoitazinagro tsoM .3891 ni V metsyS fo esaeler
1985]. ATTIS was succeeded by UNIX System Laboratories (USL), which was but would order 4BSD from Berkeley. Many installations inside the Bell System
-rosnoc NEPO/X eht ot kramedart XINU eht dessap llevoN .3991 ni llevoN ot dlos ran 4.1BSD (and replaced it with 4.3BSD when the latter became available). A
eht gnisu rof sdradnats noitacifitrec pu tes ot sthgir elos rettal eht gnivig ,muit new virtual-memory system was released with 4.4BSD. The VAX was reaching
UNIX name on products. Two years later, Novell sold UNIX to The Santa Cruz,daetsnI .enihcam taht ot detrop ton saw DSB4.4 os ,emitefil lufesu sti fo dne eht
Operation (SCO). .serutcetihcra CP letnI dna ,SPIM ,CRAPS ,00086 rewen eht no nar DSB4.4
dedulcni taht eettimmoc gnireets a yb dediug saw APRAD rof krow DSB4 ehT
Other Organizations -luc ehT .snoitutitsni cimedaca dna laicremmoc htob morf elpoep elbaton ynam
mination of the original Berkeley DARPA UNIX project was the release of 4.2BSD
tnempoleved ot del sah deifidom eb nac metsys XINU eht hcihw htiw esae ehT
in 1983; further research at Berkeley produced 4.3BSD in mid-1986. The next
si hcihw ,noitaroproC dnaR eht gnidulcni ,snoitazinagro suoremun ta krow
oneR DSB3.4 eht dna 8891 enuJ fo esaeler eohaT DSB3.4 eht dedulcni sesaeler
responsible for the Rand ports mentioned in Chapter 11; Bolt Beranek and New-
release of June 1990. These releases were primarily ports to the Computer Con-
man (BBN), who produced the direct ancestor of the 4.2BSD networking imple-
soles Incorporated hardware platform. Interleaved with these releases were two
reilrae did hcihw ,sionillI fo ytisrevinU eht ;31 retpahC ni dessucsid noitatnem
unencumbered networking releases: the 4.3BSD Netl release of March 1989 and
.)CED( noitaroproC tnempiuqE latigiD dna ;eudruP ;dravraH ;krow gnikrowten
yrateirporpnon detcartxe sesaeler esehT .1991 enuJ fo esaeler 2teN DSB3.4 eht
Probably the most widespread version of the UNIX operating system, accord-
ot mrof yranib dna ecruos ni yleerf detubirtsider eb dluoc yeht ;DSB3.4 morf edoc
ing to the number of machines on which it runs, is XENIX by Microsoft Corpora-
.esnecil ecruos XINU a yb derevoc ton erew ohw slaudividni dna taht seinapmoc
htneveS no desab yllanigiro saw XINEX .noitarepO zurC atnaS ehT dna noit
desaeler eb ot ,DSB4.4 fo snoisrev owt neeb evah ot saw esaeler GRSC lanif ehT
Edition, but later on System V More recently, SCO purchased UNIX from Novell
-birtsid yranib dna ecruos lluf lanoitidart a neeb evah ot saw enO .3991 enuJ ni
.smetsys owt eht egrem ot snalp decnuonna dna
XINU a evah ot tneipicer eht deriuqer taht ,derebmucnE-DSB4.4 dellac ,noitu
s'tfosorciM dna 2/SO s'MBI edulcni XINU no desab ton yltnenimorp smetsyS
source license. The other was to have been a subset of the source, called 4.4BSD-
XINU sa detuot neeb evah smetsys eseht llA .TN/swodniW dna 59 swodniW
a evah ot tneipicer eht eriuqer ton did dna edoc desnecil on deniatnoc taht ,etiL
killers, but none have done the deed.
UNIX source license. Following these distributions, the CSRG would be dis-
solved. The 4.4BSD-Encumbered was released as scheduled, but legal action by
snoitubirtsiD erawtfoS yelekreB
USL prevented the distribution of 4.4BSD-Lite. The legal action was resolved
The most influential of the non-Bell Laboratories and non-AT&T UNIX develop- about 1 year later, and 4.4BSD-Lite was released in April 1994. The last of the
ment groups was the University of California at Berkeley [McKusick, 1985]. money in the CSRG coffers was used to produce a bug-fixed version 4.4BSD-Lite,
Software from Berkeley is released in Berkeley Software Distributions release 2, that was distributed in June 1995. This release was the true final
(BSD)—for example, as 4.3BSD. The first Berkeley VAX UNIX work was the distribution from the CSRG.
9791 ni tnemecalper egap dna ,gnigap dnamed ,yromem lautriv fo V23 ot noitidda dna ,XINU fo snoitatnemelpmi nredom lla ni no sevil llits DSB4 ,sselehtenoN
by William Joy and Ozalp Babaoglu, to produce 3BSD [.Bsambaoegtlus y&s J ogyn, i1t9a81r]e.po rehto ynam ni