








            BBuuiillddiinngg NNeettBBSSDD KKeerrnneellss wwiitthh CCoonnffiigg


          _S_a_m_u_e_l _J_. _L_e_f_f_l_e_r _a_n_d _M_i_c_h_a_e_l _J_. _K_a_r_e_l_s


                          _A_B_S_T_R_A_C_T

          This  document describes the use of _c_o_n_f_i_g(1)
     to configure and  create  bootable  NetBSD  system
     images.  It discusses the structure of system con-
     figuration files and how to configure systems with
     non-standard  hardware  configurations.   Sections
     describing the preferred way to add  new  code  to
     the  system and how the system's autoconfiguration
     process operates are included.  An  appendix  con-
     tains a summary of the rules used by the system in
     calculating the size of  system  data  structures,
     and  also  indicates  some  of the standard system
     size limitations and how to  change  them.   Other
     configuration options are also listed.


     Revised July 5, 1993

     Revised for NetBSD beginning July 5, 2014






11..  IINNTTRROODDUUCCTTIIOONN

     _C_o_n_f_i_g  is  a  tool used in building BSD kernel images.
It takes a file describing the tunable  parameter  settings,
features, and drivers to include, and generates a collection
of files which are then used to build a copy of  the  kernel
appropriate to that configuration.  _C_o_n_f_i_g simplifies system
maintenance by isolating system dependencies  in  a  single,
easy to understand, file.

     This  document describes the content and format of sys-
tem configuration files and the rules which must be followed
when  creating these files.  Example configuration files are
constructed and discussed.

     Later sections suggest guidelines to be used in modify-
ing  system source and explain some of the inner workings of
the autoconfiguration process.  Appendix  D  summarizes  the
rules  used  in  calculating  the most important system data









Command Reference DocumentBsuilding NetBSD Kernels with Config


structures and indicates some inherent system data structure
size limitations (and how to go about modifying them).

22..  CCOONNFFIIGGUURRAATTIIOONN FFIILLEE CCOONNTTEENNTTSS

     A  system  configuration must include at least the fol-
lowing pieces of information:

+o  machine type

+o  cpu type

+o  system identification

+o  timezone

+o  maximum number of users

+o  location of the root file system

+o  available hardware

     _C_o_n_f_i_g allows multiple system images  to  be  generated
from  a single configuration description.  Each system image
is configured for identical hardware, but may have different
locations for the root file system and, possibly, other sys-
tem devices.

22..11..  MMaacchhiinnee ttyyppee

     The _m_a_c_h_i_n_e _t_y_p_e indicates if the system  is  going  to
operate on a DEC VAX-11[+] computer, or some  other  machine
on  which  NetBSD  operates.   The  machine  type is used to
locate certain data files which are  machine  specific,  and
also to select rules used in constructing the resultant con-
figuration files.

22..22..  CCppuu ttyyppee

     The _c_p_u _t_y_p_e indicates which, of possibly  many,  cpu's
the  system is to operate on.  For example, if the system is
being configured for a VAX-11, it could be running on a  VAX
8600,  VAX-11/780,  VAX-11/750,  VAX-11/730  or MicroVAX II.
(Other VAX cpu types, including the 8650, 785 and  725,  are
configured using the cpu designation for compatible machines
introduced earlier.)  Specifying  more  than  one  cpu  type
implies  that  the system should be configured to run on any
of the cpu's specified.  For some types of machines this  is
not  possible  and _c_o_n_f_i_g will print a diagnostic indicating
such.

-----------
[+]  DEC,  VAX,  UNIBUS,  MASSBUS and MicroVAX are
trademarks of Digital Equipment Corporation.









Building NetBSD Kernels with ConfiCgommand Reference Documents


22..33..  SSyysstteemm iiddeennttiiffiiccaattiioonn

     The _s_y_s_t_e_m _i_d_e_n_t_i_f_i_c_a_t_i_o_n is a moniker attached to  the
system, and often the machine on which the system is to run.
For example, at Berkeley we have machines named  Ernie  (Co-
VAX),  Kim  (No-VAX),  and  so  on.   The  system identifier
selected is used to create a global C ``#define'' which  may
be  used  to  isolate system dependent pieces of code in the
kernel.  For example, Ernie's Varian driver used to be  spe-
cial   cased   because  its  interrupt  vectors  were  wired
together.  The code in the driver which  understood  how  to
handle  this  non-standard hardware configuration was condi-
tionally compiled in only if the system was for Ernie.

     The system identifier ``GENERIC'' is given to a  system
which  will  run on any cpu of a particular machine type; it
should not otherwise be used for a system identifier.

22..44..  TTiimmeezzoonnee

     The timezone in which the system is to run is  used  to
define  the information returned by the _g_e_t_t_i_m_e_o_f_d_a_y(2) sys-
tem call.  This value is specified as the  number  of  hours
east or west of GMT.  Negative numbers indicate a value east
of GMT.  The timezone specification may  also  indicate  the
type of daylight savings time rules to be applied.

22..55..  MMaaxxiimmuumm nnuummbbeerr ooff uusseerrss

     The  system  allocates  many  system data structures at
boot time based on the maximum number of  users  the  system
will  support.   This  number  is normally between 8 and 40,
depending on the hardware and expected job mix.   The  rules
used  to  calculate  system data structures are discussed in
Appendix D.

22..66..  RRoooott ffiillee ssyysstteemm llooccaattiioonn

     When the system boots it must know the location of  the
root of the file system tree.  This location and the part(s)
of the disk(s) to be used for paging and  swapping  must  be
specified  in  order  to  create  a  complete  configuration
description.  _C_o_n_f_i_g uses many rules  to  calculate  default
locations  for  these items; these are described in Appendix
B.

     When a generic system is configured, the root file sys-
tem  is  left undefined until the system is booted.  In this
case, the root file system need not be specified, only  that
the system is a generic system.













Command Reference DocumentBsuilding NetBSD Kernels with Config


22..77..  HHaarrddwwaarree ddeevviicceess

     When the system boots it goes through an _a_u_t_o_c_o_n_f_i_g_u_r_a_-
_t_i_o_n phase.  During this period, the system searches for all
those  hardware  devices  which the system builder has indi-
cated might be present.  This probing sequence requires cer-
tain  pieces  of information such as register addresses, bus
interconnects, etc.  A system's hardware may  be  configured
in a very flexible manner or be specified without any flexi-
bility whatsoever.  Most people do  not  configure  hardware
devices into the system unless they are currently present on
the machine, expect them to be present in the  near  future,
or  are simply guarding against a hardware failure somewhere
else at the site (it is often wise  to  configure  in  extra
disks in case an emergency requires moving one off a machine
which has hardware problems).

     The specification of hardware devices usually  occupies
the  majority  of  the configuration file.  As such, a large
portion of this document will  be  spent  understanding  it.
Section  6.3 contains a description of the autoconfiguration
process, as it applies to those planning to write, or modify
existing, device drivers.

22..88..  PPsseeuuddoo ddeevviicceess

     Several  system  facilities  are configured in a manner
like that used for hardware devices although  they  are  not
associated with specific hardware.  These system options are
configured as _p_s_e_u_d_o_-_d_e_v_i_c_e_s.  Some pseudo devices allow  an
optional  parameter  that  sets  the  limit on the number of
instances of the device that are active simultaneously.

22..99..  SSyysstteemm ooppttiioonnss

     Other  than  the  mandatory   pieces   of   information
described  above,  it  is  also  possible to include various
optional system facilities  or  to  modify  system  behavior
and/or  limits.   For  example,  NetBSD can be configured to
support binary compatibility for programs built under  Linux
and  FreeBSD.   Also,  optional support is provided for disk
quotas and tracing the performance  of  the  virtual  memory
subsystem.   Any  optional  facilities to be configured into
the system are specified in  the  configuration  file.   The
resultant  files  generated  by  _c_o_n_f_i_g  will  automatically


















Building NetBSD Kernels with ConfiCgommand Reference Documents


include the necessary pieces of the system.

33..  SSYYSSTTEEMM BBUUIILLDDIINNGG PPRROOCCEESSSS

     In this section we  consider  the  steps  necessary  to
build  a bootable system image.  We assume the system source
is located in the  ``/usr/src''  directory  and  that,  ini-
tially, the system is being configured from source code.

     Under  normal circumstances there are 5 steps in build-
ing a system.

1) Create a configuration file for the system.

2) Make a directory for the system to be constructed in.

3) Run _c_o_n_f_i_g on the  configuration  file  to  generate  the
   files required to compile and load the system image.

4) Construct  the  source code interdependency rules for the
   configured system with _m_a_k_e _d_e_p_e_n_d using _m_a_k_e(1).

5) Compile and link the system with _m_a_k_e.

     Steps 1 and 2 are usually done only once.  When a  sys-
tem  configuration  changes  it usually suffices to just run
_c_o_n_f_i_g on  the  modified  configuration  file,  rebuild  the
source code dependencies, and remake the system.  Sometimes,
however, configuration dependencies may not  be  noticed  in
which  case  it  is  necessary to clean out the object files
saved in the system's  directory;  this  will  be  discussed
later.

33..11..  CCrreeaattiinngg aa ccoonnffiigguurraattiioonn ffiillee

     Configuration  files  normally  reside in the directory
``conf'' in the architecture-specific subtree of the  kernel
for  the  machine  type in use.  (For example, configuration
files    for     64-bit     x86     machines     live     in
``/usr/src/sys/arch/amd64/conf''.)   A configuration file is
most easily constructed by copying an existing configuration
file  and  modifying  it.   The NetBSD distribution contains
assorted standard configuration files for different  machine
types  and varieties.  Start with ``GENERIC'' if no other is
more appropriate.

     The configuration file must have the same name  as  the
directory  in  which  the  configured system is to be built.
Further, _c_o_n_f_i_g assumes this directory is located under  the
``compile''  directory  at  the  same  level as the ``conf''
directory in which  it is run.   For  example,  the  generic
64-bit    x86    system    has    a    configuration    file
``/usr/src/sys/arch/amd64/conf/GENERIC'' and an accompanying
directory named ``/usr/src/sys/arch/amd64/compile/GENERIC''.









Command Reference DocumentBsuilding NetBSD Kernels with Config


Although it is not required that the system sources and con-
figuration  files  reside in ``/usr/src,'' the configuration
and compilation procedure depends on the relative  locations
of  directories within that hierarchy, as most of the system
code and the files created by _c_o_n_f_i_g use  pathnames  of  the
form ``../''.

     When  building  the  configuration  file,  be  sure  to
include the items described in section  2.   In  particular,
the  machine  type,  cpu  type, timezone, system identifier,
maximum users, and root device must be specified.  The spec-
ification  of  the  hardware present may take a bit of work;
particularly if your hardware is configured at  non-standard
places  (e.g.  device  registers  located at funny places or
devices not supported by the system).   Section  4  of  this
document  gives  a detailed description of the configuration
file syntax, section 5 explains  some  sample  configuration
files, and section 6 discusses how to add new devices to the
system.  If the devices to be  configured  are  not  already
described  in  one  of  the existing configuration files you
should check the section 4 manual pages.  For each supported
device,  the  manual page synopsis entry gives a sample con-
figuration line.

     Once the configuration file is complete, run it through
_c_o_n_f_i_g  and look for any errors.  Never try and use a system
which _c_o_n_f_i_g has complained about; the  results  are  unpre-
dictable.  For the most part, _c_o_n_f_i_g's error diagnostics are
self explanatory.  It may be the case that the line  numbers
given with the error messages are off by one.

     A  successful  run of _c_o_n_f_i_g on your configuration file
will generate a number of files in the configuration  direc-
tory.  These files are:

+o  A file to be used by _m_a_k_e(1) in compiling and loading the
   system, _M_a_k_e_f_i_l_e.

+o  One file for each possible system image for this machine,
   _s_w_a_p_x_x_x_._c,  where  _x_x_x  is  the name of the system image,
   which describes where swapping, the root file system, and
   other miscellaneous system devices are located.

+o  A collection of header files, one per possible device the
   system supports, which define the hardware configured.

+o  A file containing the I/O configuration  tables  used  by
   the  system during its _a_u_t_o_c_o_n_f_i_g_u_r_a_t_i_o_n phase, _i_o_c_o_n_f_._c.

+o  An assembly language file of interrupt vectors which con-
   nect  interrupts from the machine's external buses to the
   main system path for handling interrupts, and a file that
   contains counters and names for the interrupt vectors.










Building NetBSD Kernels with ConfiCgommand Reference Documents


     Unless  you have reason to doubt _c_o_n_f_i_g, or are curious
how the system's autoconfiguration scheme works, you  should
never have to look at any of these files.

33..22..  CCoonnssttrruuccttiinngg ssoouurrccee ccooddee ddeeppeennddeenncciieess

     When _c_o_n_f_i_g is done generating the files needed to com-
pile and link your system it will terminate with  a  message
of  the form ``Don't forget to run make depend''.  This is a
reminder that you should change over  to  the  configuration
directory  for  the  system  just configured and type ``make
depend'' to build the rules used by _m_a_k_e to recognize inter-
dependencies  in  the  system source code.  This will insure
that any changes to a piece of the system source  code  will
result  in the proper modules being recompiled the next time
_m_a_k_e is run.

     This step is particularly important if your site  makes
changes  to  the  system include files.  The rules generated
specify which source  code  files  are  dependent  on  which
include files.  Without these rules, _m_a_k_e will not recognize
when it must rebuild modules due to the  modification  of  a
system header file.  The dependency rules are generated by a
pass of the C preprocessor and  reflect  the  global  system
options.   This step must be repeated when the configuration
file is changed and _c_o_n_f_i_g is used to regenerate the  system
makefile.

33..33..  BBuuiillddiinngg tthhee ssyysstteemm

     The  makefile  constructed by _c_o_n_f_i_g should allow a new
system to be rebuilt by simply typing  ``make''.   Alternate
system  image names are used when the root file system loca-
tion and/or swapping configuration is done in more than  one
way.  The makefile which _c_o_n_f_i_g creates has entry points for
each system image defined in the configuration file.   Thus,
if  you  have  configured ``netbsd'' to be a system with the
root file system on an ``hp'' device and ``hknetbsd'' to  be
a system with the root file system on an ``hk'' device, then
``make netbsd hknetbsd'' will  generate  binary  images  for
each.   As the system will generally use the disk from which
it is loaded as the root filesystem, separate system  images
are  only required to support different swap configurations.

     Note that the name of a  bootable  image  is  different
from the system identifier.  All bootable images are config-
ured for the same system; only  the  information  about  the
root  file  system  and  paging  devices  differ.   (This is
described in more detail in section 4.)

     The last step in the  system  building  process  is  to
rearrange  certain commonly used symbols in the symbol table
of the system image;  the makefile generated by _c_o_n_f_i_g  does
this  automatically  for  you.   This  is  advantageous  for









Command Reference DocumentBsuilding NetBSD Kernels with Config


programs such as _n_e_t_s_t_a_t(1) and _v_m_s_t_a_t(1),  which  run  much
faster  when  the symbols they need are located at the front
of the symbol  table.   Remember  also  that  many  programs
expect   the   currently   executing   system  to  be  named
``/netbsd''.  If you install a new system and name it  some-
thing  other  than  ``/netbsd'', many programs are likely to
give strange results.

33..44..  SShhaarriinngg oobbjjeecctt mmoodduulleess

     If you have many systems which are all built on a  sin-
gle machine there are at least two approaches to saving time
in building system images.  The best way is to have a single
system  image which is run on all machines.  This is attrac-
tive since it minimizes disk space used and time required to
rebuild  systems after making changes.  However, it is often
the case that one or more systems will require a  separately
configured  system image.  This may be due to limited memory
(building a system with many unused device  drivers  can  be
expensive),  or  to  configuration requirements (one machine
may be a development  machine  where  disk  quotas  are  not
needed,  while  another  is  a production machine where they
are), etc.  In these cases it is possible for common systems
to share relocatable object modules which are not configura-
tion dependent.

     To share object modules, a  generic  system  should  be
built.   Then,  for  each  system  configure  the  system as
before, but before recompiling and linking the system,  type
``make  links''  in  the system compilation directory.  This
will cause the system to  be  searched  for  source  modules
which  are  safe  to share between systems and generate sym-
bolic links in the  current  directory  to  the  appropriate
object  modules  in  the  directory ``../GENERIC''.  A shell
script, ``makelinks'' is generated with this request and may
be  checked for correctness.  The file ``/sys/conf/defines''
contains a list of symbols which  we  believe  are  safe  to
ignore  when  checking the source code for modules which may
be shared.  Note that this  list  includes  the  definitions
used  to conditionally compile in the virtual memory tracing
facilities, and the trace point  support  used  only  rarely
(even at Berkeley).  It may be necessary to modify this file
to reflect local needs.  Note further that interdependencies
which  are  not  directly visible in the source code are not
caught.  This means that if you place  per-system  dependen-
cies in an include file, they will not be recognized and the
shared code may be selected in an unexpected fashion.

33..55..  BBuuiillddiinngg pprrooffiilleedd ssyysstteemmss

     It is simple to configure a system which will automati-
cally  collect  profiling  information  as it operates.  The
profiling data may be collected with _k_g_m_o_n(8) and  processed
with  _g_p_r_o_f(1)  to obtain information regarding the system's









Building NetBSD Kernels with ConfiCgommand Reference Documents


operation.  Profiled systems maintain histograms of the pro-
gram  counter  as  well as the number of invocations of each
routine.  The _g_p_r_o_f command will  also  generate  a  dynamic
call  graph of the executing system and propagate time spent
in each routine along the arcs of the  call  graph  (consult
the  _g_p_r_o_f  documentation  for  elaboration).   The  program
counter sampling can be driven by the system  clock,  or  if
you  have  an  alternate  real time clock, this can be used.
The latter is highly recommended, as use of the system clock
will  result in statistical anomalies, and time spent in the
clock routine will not be accurately attributed.

     To configure a profiled system, the --pp option should be
supplied to _c_o_n_f_i_g.  A profiled system is about 5-10% larger
in its text space due to the calls to count  the  subroutine
invocations.   When  the system executes, the profiling data
is stored in a buffer which is 1.2 times  the  size  of  the
text  space.   The  overhead  for  running a profiled system
varies; under normal load we see anywhere from 5-25% of  the
system time spent in the profiling code.

     Note  that  systems configured for profiling should not
be shared as described above unless  all  the  other  shared
systems are also to be profiled.

44..  CCOONNFFIIGGUURRAATTIIOONN FFIILLEE SSYYNNTTAAXX

     In  this section we consider the specific rules used in
writing a configuration file.  A complete  grammar  for  the
input  language can be found in Appendix A and may be of use
if you should have problems with syntax errors.

     A configuration file is broken up  into  three  logical
pieces:

+o  configuration  parameters  global  to  all  system images
   specified in the configuration file,

+o  parameters specific to each system image to be generated,
   and

+o  device specifications.

44..11..  GGlloobbaall ccoonnffiigguurraattiioonn ppaarraammeetteerrss

     The  global  configuration  parameters  are the type of
machine, cpu types, options,  timezone,  system  identifier,
and  maximum  users.  Each is specified with a separate line
in the configuration file.

mmaacchhiinnee _t_y_p_e
     The system is to run on the machine type specified.  No
     more than one machine type can appear in the configura-
     tion file.  Legal values are vvaaxx and ssuunn.









Command Reference DocumentBsuilding NetBSD Kernels with Config


ccppuu ``_t_y_p_e''
     This system is to run on the cpu type specified.   More
     than one cpu type specification can appear in a config-
     uration file.   Legal  types  for  a  vvaaxx  machine  are
     VVAAXX88660000,  VVAAXX778800,  VVAAXX775500,  VVAAXX773300 and VVAAXX663300 (MicroVAX
     II).  The 8650 is listed as an 8600, the 785 as a  780,
     and a 725 as a 730.

ooppttiioonnss _o_p_t_i_o_n_l_i_s_t
     Compile  the  listed  optional  code  into  the system.
     Options in this list are separated by commas.  Possible
     options  are listed at the top of the generic makefile.
     A line of the  form  ``options  FUNNY,HAHA''  generates
     global  ``#define''s  -DFUNNY  -DHAHA  in the resultant
     makefile.  An option may be given a value by  following
     its  name  with ``=='', then the value enclosed in (dou-
     ble) quotes.  The following are major options are  cur-
     rently  in  use: COMPAT (include code for compatibility
     with 4.1BSD  binaries),  INET  (Internet  communication
     protocols),  NS (Xerox NS communication protocols), and
     QUOTA (enable disk quotas).  Other kernel options  con-
     trolling system sizes and limits are listed in Appendix
     D; options for the network are  found  in  Appendix  E.
     There  are additional options which are associated with
     certain peripheral devices; those  are  listed  in  the
     Synopsis section of the manual page for the device.

mmaakkeeooppttiioonnss _o_p_t_i_o_n_l_i_s_t
     Options  that  are  used within the system makefile and
     evaluated by _m_a_k_e are listed as  _m_a_k_e_o_p_t_i_o_n_s.   Options
     are  listed  with  their values with the form ``makeop-
     tions name=value,name2=value2.''  The  values  must  be
     enclosed  in  double quotes if they include numerals or
     begin with a dash.

ttiimmeezzoonnee _n_u_m_b_e_r [ ddsstt [ _n_u_m_b_e_r ] ]
     Specifies the timezone used by  the  system.   This  is
     measured  in  the number of hours your timezone is west
     of GMT.  EST is 5 hours west of GMT, PST is  8.   Nega-
     tive  numbers indicate hours east of GMT.  If you spec-
     ify ddsstt, the system will operate under daylight savings
     time.  An optional integer or floating point number may
     be included to specify  a  particular  daylight  saving
     time  correction  algorithm;  the  default  value is 1,
     indicating the United  States.   Other  values  are:  2
     (Australian  style),  3  (Western  European), 4 (Middle
     European), and 5 (Eastern  European).   See  _g_e_t_t_i_m_e_o_f_-
     _d_a_y(2) and _c_t_i_m_e(3) for more information.

iiddeenntt _n_a_m_e
     This  system is to be known as _n_a_m_e.  This is usually a
     cute name  like  ERNIE  (short  for  Ernie  Co-Vax)  or
     VAXWELL (for Vaxwell Smart).  This value is defined for
     use in conditional compilation, and  is  also  used  to









Building NetBSD Kernels with ConfiCgommand Reference Documents


     locate  an  optional  list  of source files specific to
     this system.

mmaaxxuusseerrss _n_u_m_b_e_r
     The maximum expected number  of  simultaneously  active
     user  on this system is _n_u_m_b_e_r.  This number is used to
     size several system data structures.

44..22..  SSyysstteemm iimmaaggee ppaarraammeetteerrss

     Multiple bootable images may be specified in  a  single
configuration  file.   The systems will have the same global
configuration parameters and devices, but  the  location  of
the  root  file system and other system specific devices may
be different.  A system image is specified with a ``config''
line:

     ccoonnffiigg _s_y_s_n_a_m_e _c_o_n_f_i_g_-_c_l_a_u_s_e_s

The  _s_y_s_n_a_m_e  field  is  the name given to the loaded system
image; almost everyone names  their  standard  system  image
``netbsd''.  The configuration clauses are one or more spec-
ifications indicating where the root file system is  located
and  the  number and location of paging devices.  The device
used  by  the  system  to  process  argument  lists   during
_e_x_e_c_v_e(2)  calls  may  also be specified, though in practice
this is almost always selected by _c_o_n_f_i_g using  one  of  its
rules for selecting default locations for system devices.

     A configuration clause is one of the following

     rroooott [ oonn ] _r_o_o_t_-_d_e_v_i_c_e
     sswwaapp [ oonn ] _s_w_a_p_-_d_e_v_i_c_e [ aanndd _s_w_a_p_-_d_e_v_i_c_e ] ...
     dduummppss [ oonn ] _d_u_m_p_-_d_e_v_i_c_e
     aarrggss [ oonn ] _a_r_g_-_d_e_v_i_c_e

(the  ``on''  is  optional.)  Multiple configuration clauses
are separated by white space; _c_o_n_f_i_g  allows  specifications
to  be continued across multiple lines by beginning the con-
tinuation line with a tab character.   The  ``root''  clause
specifies  where  the  root  file  system  is  located,  the
``swap'' clause indicates swapping and paging  area(s),  the
``dumps''  clause  can  be  used to force system dumps to be
taken on a particular device, and the ``args'' clause can be
used  to  specify  that  argument list processing for _e_x_e_c_v_e
should be done on a particular device.

     The device names supplied in the clauses may  be  fully
specified  as  a device, unit, and file system partition; or
underspecified in which case _c_o_n_f_i_g will use  builtin  rules
to  select  default unit numbers and file system partitions.
The defaulting rules are  a  bit  complicated  as  they  are
dependent on the overall system configuration.  For example,
the swap area need not be  specified  at  all  if  the  root









Command Reference DocumentBsuilding NetBSD Kernels with Config


device is specified; in this case the swap area is placed in
the ``b'' partition of the same disk  where  the  root  file
system  is  located.  Appendix B contains a complete list of
the defaulting rules used in selecting system  configuration
devices.

     The  device  names  are  translated  to the appropriate
major and minor device numbers on a  per-machine  basis.   A
file,  ``/sys/conf/devices.machine''  (where  ``machine'' is
the machine type specified in the  configuration  file),  is
used  to map a device name to its major block device number.
The minor device number is  calculated  using  the  standard
disk partitioning rules: on unit 0, partition ``a'' is minor
device 0, partition ``b'' is minor device 1, and so on;  for
units  other  than 0, add 8 times the unit number to get the
minor device.

     If the default mapping of device  name  to  major/minor
device number is incorrect for your configuration, it can be
replaced by an explicit  specification  of  the  major/minor
device.  This is done by substituting

     mmaajjoorr _x mmiinnoorr _y

where the device name would normally be found.  For example,

     ccoonnffiigg kernel rroooott oonn mmaajjoorr 99 mmiinnoorr 1

     Normally, the areas configured for swap space are sized
by the system at boot time.  If a non-standard size is to be
used for one or more swap areas (less than the  full  parti-
tion),  this  can also be specified.  To do this, the device
name specified for a swap area should have a ``size'' speci-
fication appended.  For example,

     ccoonnffiigg kernel rroooott oonn hp0 sswwaapp oonn hp0b ssiizzee 1200

would  force  swapping  to  be  done  in  partition ``b'' of
``hp0'' and the swap partition size would  be  set  to  1200
sectors.   A swap area sized larger than the associated disk
partition is trimmed to the partition size.

     To create a  generic  configuration,  only  the  clause
``swap generic'' should be specified; any extra clauses will
cause an error.

44..33..  DDeevviiccee ssppeecciiffiiccaattiioonnss

     Each device attached to a machine must be specified  to
_c_o_n_f_i_g  so  that the system generated will know to probe for
it during the autoconfiguration process carried out at  boot
time.   Hardware  specified  in  the  configuration need not
actually be present on the machine where the generated  sys-
tem  is to be run.  Only the hardware actually found at boot









Building NetBSD Kernels with ConfiCgommand Reference Documents


time will be used by the system.

     The specification of hardware devices in the configura-
tion  file  parallels  the  interconnection hierarchy of the
machine to be configured.  On the VAX,  this  means  that  a
configuration  file  must  indicate  what MASSBUS and UNIBUS
adapters are present, and to which _n_e_x_i they might  be  con-
nected.*   Similarly,  devices and controllers must be indi-
cated as possibly being connected to one or  more  adapters.
A  device  description  may provide a complete definition of
the possible configuration parameters or it may  leave  cer-
tain  parameters undefined and make the system probe for all
the possible values.  The latter allows a single device con-
figuration  list  to match many possible physical configura-
tions.  For example, a disk may be indicated as  present  at
UNIBUS  adapter 0, or at any UNIBUS adapter which the system
locates at boot time.  The latter scheme,  termed  _w_i_l_d_c_a_r_d_-
_i_n_g,  allows  more flexibility in the physical configuration
of a system; if a disk must be moved around for some reason,
the system will still locate it at the alternate location.

     A  device  specification  takes  one  of  the following
forms:

     mmaasstteerr _d_e_v_i_c_e_-_n_a_m_e _d_e_v_i_c_e_-_i_n_f_o
     ccoonnttrroolllleerr _d_e_v_i_c_e_-_n_a_m_e _d_e_v_i_c_e_-_i_n_f_o [ _i_n_t_e_r_r_u_p_t_-_s_p_e_c ]
     ddeevviiccee _d_e_v_i_c_e_-_n_a_m_e _d_e_v_i_c_e_-_i_n_f_o _i_n_t_e_r_r_u_p_t_-_s_p_e_c
     ddiisskk _d_e_v_i_c_e_-_n_a_m_e _d_e_v_i_c_e_-_i_n_f_o
     ttaappee _d_e_v_i_c_e_-_n_a_m_e _d_e_v_i_c_e_-_i_n_f_o

A ``master'' is a MASSBUS tape controller; a  ``controller''
is  a  disk  controller, a UNIBUS tape controller, a MASSBUS
adapter, or a UNIBUS adapter.  A ``device'' is an autonomous
device  which  connects  directly  to  a  UNIBUS adapter (as
opposed to something like a disk which  connects  through  a
disk  controller).   ``Disk''  and  ``tape''  identify  disk
drives and tape drives  connected  to  a  ``controller''  or
``master.''

     The _d_e_v_i_c_e_-_n_a_m_e is one of the standard device names, as
indicated in section 4 of the UNIX Programmers Manual,  con-
catenated  with  the  _l_o_g_i_c_a_l unit number to be assigned the
device (the _l_o_g_i_c_a_l unit number may be  different  than  the
_p_h_y_s_i_c_a_l  unit  number  indicated  on the front of something
like a disk; the _l_o_g_i_c_a_l unit number is used to refer to the
UNIX  device,  not  the physical unit number).  For example,
``hp0'' is logical unit 0 of a MASSBUS storage device,  even
though it might be physical unit 3 on MASSBUS adapter 1.


-----------
*  While  VAX-11/750's and VAX-11/730 do not actu-
ally have nexi, the system treats them  as  having
_s_i_m_u_l_a_t_e_d _n_e_x_i to simplify device configuration.









Command Reference DocumentBsuilding NetBSD Kernels with Config


     The  _d_e_v_i_c_e_-_i_n_f_o  clause  specifies how the hardware is
connected in the interconnection  hierarchy.   On  the  VAX,
UNIBUS  and  MASSBUS  adapters are connected to the internal
system bus through a _n_e_x_u_s.   Thus,  one  of  the  following
specifications would be used:

     ccoonnttrroolllleerr     mba0      aatt nneexxuuss _x
     ccoonnttrroolllleerr     uba0      aatt nneexxuuss _x

To tie a controller to a specific nexus, ``x'' would be sup-
plied as the number of that nexus; otherwise  ``x''  may  be
specified  as ``?'', in which case the system will probe all
nexi present looking for the specified controller.

     The remaining interconnections on the VAX are:

+o  a controller may be connected to another controller (e.g.
   a disk controller attached to a UNIBUS adapter),

+o  a  master  is  always attached to a controller (a MASSBUS
   adapter),

+o  a tape is always attached to a master (for  MASSBUS  tape
   drives),

+o  a disk is always attached to a controller, and

+o  devices  are  always attached to controllers (e.g. UNIBUS
   controllers attached to UNIBUS adapters).

The following lines give an example of each of these  inter-
connections:

     ccoonnttrroolllleerr     hk0       aatt uba0 ...
     mmaasstteerr         ht0       aatt mba0 ...
     ddiisskk           hp0       aatt mba0 ...
     ttaappee           tu0       aatt ht0 ...
     ddiisskk           rk1       aatt hk0 ...
     ddeevviiccee         dz0       aatt uba0 ...

Any  piece  of hardware which may be connected to a specific
controller may  also  be  wildcarded  across  multiple  con-
trollers.

     The  final piece of information needed by the system to
configure devices is some  indication  of  where  or  how  a
device will interrupt.  For tapes and disks, simply specify-
ing the _s_l_a_v_e or _d_r_i_v_e number is sufficient  to  locate  the
control  status  register for the device.  _D_r_i_v_e numbers may
be wildcarded on MASSBUS devices, but  not  on  disks  on  a
UNIBUS controller.  For controllers, the control status reg-
ister must be given explicitly, as well the number of inter-
rupt  vectors  used  and  the names of the routines to which
they should be bound.  Thus the example  lines  given  above









Building NetBSD Kernels with ConfiCgommand Reference Documents


might be completed as:

     ccoonnttrroolllleerr     hk0       aatt uba0 ccssrr 0177440vveeccttoorr rkintr
     mmaasstteerr         ht0       aatt mba0 ddrriivvee 0
     ddiisskk           hp0       aatt mba0 ddrriivvee ?
     ttaappee           tu0       aatt ht0 ssllaavvee 0
     ddiisskk           rk1       aatt hk0 ddrriivvee 1
     ddeevviiccee         dz0       aatt uba0 ccssrr 0160100vveeccttoorr dzrint dzxint

     Certain device drivers require extra information passed
to them at boot time to tailor their operation to the actual
hardware  present.   The  line  printer driver, for example,
needs to know how many columns are present on each non-stan-
dard  line  printer  (i.e. a line printer with other than 80
columns).  The drivers for the terminal multiplexors need to
know  which lines are attached to modem lines so that no one
will be allowed to use them unless a connection is  present.
For  this  reason,  one last parameter may be specified to a
_d_e_v_i_c_e, a _f_l_a_g_s field.  It has the syntax

     ffllaaggss _n_u_m_b_e_r

and is usually placed after the _c_s_r specification.  The _n_u_m_-
_b_e_r is passed directly to the associated driver.  The manual
pages in section 4 should be consulted to determine how each
driver  uses  this value (if at all).  Communications inter-
face drivers commonly use  the  flags  to  indicate  whether
modem control signals are in use.

     The  exact  syntax for each specific device is given in
the Synopsis section of its manual page in section 4 of  the
manual.

44..44..  PPsseeuuddoo--ddeevviicceess

     A number of drivers and software subsystems are treated
like device drivers without  any  associated  hardware.   To
include  any of these pieces, a ``pseudo-device'' specifica-
tion must be used.  A  specification  for  a  pseudo  device
takes the form

     ppsseeuuddoo--ddeevviiccee  _d_e_v_i_c_e_-_n_a_m_e [ _h_o_w_m_a_n_y ]

     Examples of pseudo devices are ppttyy, the pseudo terminal
driver (where the optional _h_o_w_m_a_n_y value indicates the  num-
ber of pseudo terminals to configure, 32 default), and lloooopp,
the  software  loopback  network  pseudo-interface.    Other
pseudo  devices for the network include iimmpp (required when a
CSS or ACC imp is configured) and eetthheerr (used by the Address
Resolution  Protocol on 10 Mb/sec Ethernets).  More informa-
tion on configuring each of these can also be found in  sec-












Command Reference DocumentBsuilding NetBSD Kernels with Config


tion 4 of the manual.

55..  SSAAMMPPLLEE CCOONNFFIIGGUURRAATTIIOONN FFIILLEESS

     In  this  section  we  will consider how to configure a
sample VAX-11/780 system on which the hardware can be recon-
figured  to guard against various hardware mishaps.  We then
study the rules needed to configure a VAX-11/750 to run in a
networking environment.

55..11..  VVAAXX--1111//778800 SSyysstteemm

     Our  VAX-11/780 is configured with hardware recommended
in the document ``Hints on Configuring a  VAX  for  4.2BSD''
(this is one of the high-end configurations).  Table 1 lists
the pertinent hardware to be configured.


+---------------------+---------+------------+--------+-----------+
|Item                 | Vendor  | Connection | Name   | Reference |
+---------------------+---------+------------+--------+-----------+
|cpu                  | DEC     |            | VAX780 |           |
|MASSBUS controller   | Emulex  | nexus ?    | mba0   | hp(4)     |
|disk                 | Fujitsu | mba0       | hp0    |           |
|disk                 | Fujitsu | mba0       | hp1    |           |
|MASSBUS controller   | Emulex  | nexus ?    | mba1   |           |
|disk                 | Fujitsu | mba1       | hp2    |           |
|disk                 | Fujitsu | mba1       | hp3    |           |
|UNIBUS adapter       | DEC     | nexus ?    |        |           |
|tape controller      | Emulex  | uba0       | tm0    | tm(4)     |
|tape drive           | Kennedy | tm0        | te0    |           |
|tape drive           | Kennedy | tm0        | te1    |           |
|terminal multiplexor | Emulex  | uba0       | dh0    | dh(4)     |
|terminal multiplexor | Emulex  | uba0       | dh1    |           |
|terminal multiplexor | Emulex  | uba0       | dh2    |           |
+---------------------+---------+------------+--------+-----------+

           Table 1.  VAX-11/780 Hardware support.

We will call this machine ANSEL and construct  a  configura-
tion file one step at a time.

     The  first  step is to fill in the global configuration
parameters.  The machine is a VAX, so the  _m_a_c_h_i_n_e  _t_y_p_e  is
``vax''.   We  will assume this system will run only on this
one processor, so the _c_p_u _t_y_p_e is ``VAX780''.   The  options
are  empty since this is going to be a ``vanilla'' VAX.  The
system identifier, as mentioned before,  is  ``ANSEL,''  and
the  maximum number of users we plan to support is about 40.
Thus the beginning of  the  configuration  file  looks  like
this:












Building NetBSD Kernels with ConfiCgommand Reference Documents


     #
     # ANSEL VAX (a picture perfect machine)
     #
     machine        vax
     cpu            VAX780
     timezone       8 dst
     ident          ANSEL
     maxusers       40


     To  this  we must then add the specifications for three
system images.  The first will be our standard  system  with
the  root  on  ``hp0'' and swapping on the same drive as the
root.  The second will have the root file system in the same
location,  but  swap  space interleaved among drives on each
controller.  Finally, the third will be a generic system, to
allow us to boot off any of the four disk drives.

     config         kernel    root on hp0
     config         hpkernel  root on hp0 swap on hp0 and hp2
     config         genkernel swap generic


     Finally,  the hardware must be specified.  Let us first
just try transcribing the information from Table 1.

     controller     mba0      at nexus ?
     disk           hp0       at mba0 disk 0
     disk           hp1       at mba0 disk 1
     controller     mba1      at nexus ?
     disk           hp2       at mba1 disk 2
     disk           hp3       at mba1 disk 3
     controller     uba0      at nexus ?
     controller     tm0       at uba0 csr 0172520vector tmintr
     tape           te0       at tm0 drive 0
     tape           te1       at tm0 drive 1
     device         dh0       at uba0 csr 0160020vector dhrint dhxint
     device         dm0       at uba0 csr 0170500vector dmintr
     device         dh1       at uba0 csr 0160040vector dhrint dhxint
     device         dh2       at uba0 csr 0160060vector dhrint dhxint


(Oh, I forgot to mention one panel of  the  terminal  multi-
plexor has modem control, thus the ``dm0'' device.)

     This  will suffice, but leaves us with little flexibil-
ity.  Suppose our first disk controller were to  break.   We
would like to recable the drives normally on the second con-
troller so that all our disks could still  be  used  without
reconfiguring  the system.  To do this we wildcard the MASS-
BUS adapter connections and also the  slave  numbers.   Fur-
ther,  we wildcard the UNIBUS adapter connections in case we
decide some time in the future to purchase  another  adapter
to offload the single UNIBUS we currently have.  The revised









Command Reference DocumentBsuilding NetBSD Kernels with Config


device specifications would then be:

     controller     mba0      at nexus ?
     disk           hp0       at mba? disk ?
     disk           hp1       at mba? disk ?
     controller     mba1      at nexus ?
     disk           hp2       at mba? disk ?
     disk           hp3       at mba? disk ?
     controller     uba0      at nexus ?
     controller     tm0       at uba? csr 0172520vector tmintr
     tape           te0       at tm0 drive 0
     tape           te1       at tm0 drive 1
     device         dh0       at uba? csr 0160020vector dhrint dhxint
     device         dm0       at uba? csr 0170500vector dmintr
     device         dh1       at uba? csr 0160040vector dhrint dhxint
     device         dh2       at uba? csr 0160060vector dhrint dhxint


The completed configuration file for ANSEL is shown  in  Ap-
pendix C.

55..22..  VVAAXX--1111//775500 wwiitthh nneettwwoorrkk ssuuppppoorrtt

     Our  VAX-11/750  system  will  be located on two 10Mb/s
Ethernet local area networks and also  the  DARPA  Internet.
The  system will have a MASSBUS drive for the root file sys-
tem and two UNIBUS drives.  Paging is interleaved among  all
three drives.  We have sold our standard DEC terminal multi-
plexors since this machine will be accessed  solely  through
the  network.   This machine is not intended to have a large
user community, it does not have a  great  deal  of  memory.
First the global parameters:

     #
     # UCBVAX (Gateway to the world)
     #
     machine        vax
     cpu            "VAX780"
     cpu            "VAX750"
     ident          UCBVAX
     timezone       8 dst
     maxusers       32
     options        INET
     options        NS


     The  multiple cpu types allow us to replace UCBVAX with
a more powerful cpu without reconfiguring the  system.   The
value of 32 given for the maximum number of users is done to
force the system data structures to be over-allocated.  That
is  desirable  on  this  machine  because,  while  it is not
expected to support many users, it is expected to perform  a
great  deal of work.  The ``INET'' indicates that we plan to
use the DARPA standard Internet protocols on  this  machine,









Building NetBSD Kernels with ConfiCgommand Reference Documents


and  ``NS''  also  includes  support for Xerox NS protocols.
Note that unlike 4.2BSD  configuration  files,  the  network
protocol   options   do  not  require  corresponding  pseudo
devices.

     The system images and disks are configured next.

     config         kernel    root on hp swap on hp and rk0 and rk1
     config         upkernel  root on up
     config         hkkernel  root on hk swap on rk0 and rk1

     controller     mba0      at nexus ?
     controller     uba0      at nexus ?
     disk           hp0       at mba? drive 0
     disk           hp1       at mba? drive 1
     controller     sc0       at uba? csr 0176700vector upintr
     disk           up0       at sc0 drive 0
     disk           up1       at sc0 drive 1
     controller     hk0       at uba? csr 0177440 vector rkintr
     disk           rk0       at hk0 drive 0
     disk           rk1       at hk0 drive 1


     UCBVAX requires heavy interleaving of its  paging  area
to keep up with all the mail traffic it handles.  The limit-
ing factor on this system's performance is usually the  num-
ber  of  disk arms, as opposed to memory or cpu cycles.  The
extra UNIBUS controller, ``sc0'', is  in  case  the  MASSBUS
controller  breaks  and a spare controller must be installed
(most of our old UNIBUS controllers have been replaced  with
the  newer MASSBUS controllers, so we have a number of these
around as spares).

     Finally, we add in the network devices.  Pseudo  termi-
nals  are needed to allow users to log in across the network
(remember the only hardwired terminal is the console).   The
software  loopback  device is used for on-machine communica-
tions.  The connection to the Internet is  through  an  IMP,
this  requires yet another _p_s_e_u_d_o_-_d_e_v_i_c_e (in addition to the
actual hardware device used  by  the  IMP  software).   And,
finally,  there  are  the two Ethernet devices.  These use a
special protocol, the Address Resolution Protocol (ARP),  to
map  between  Internet  and  Ethernet  addresses.  Thus, yet
another _p_s_e_u_d_o_-_d_e_v_i_c_e  is  needed.   The  additional  device
specifications are show below.

     pseudo-device  pty
     pseudo-device  loop
     pseudo-device  imp
     device         acc0      at uba? csr 0167600vector accrint accxint
     pseudo-device  ether
     device         ec0       at uba? csr 0164330vector ecrint eccollide ecxint
     device         il0       at uba? csr 0164000vector ilrint ilcint










Command Reference DocumentBsuilding NetBSD Kernels with Config


The  completed configuration file for UCBVAX is shown in Ap-
pendix C.

55..33..  MMiisscceellllaanneeoouuss ccoommmmeennttss

     It should be noted in these examples that neither  sys-
tem was configured to use disk quotas or the 4.1BSD compati-
bility mode.  To use these optional facilities, and  others,
we  would  probably  clean  out  our  current configuration,
reconfigure the system, then recompile and relink the system
image(s).  This could, of course, be avoided by figuring out
which relocatable object files are affected by the reconfig-
uration, then reconfiguring and recompiling only those files
affected by the configuration change.  This technique should
be used carefully.

66..  AADDDDIINNGG NNEEWW SSYYSSTTEEMM SSOOFFTTWWAARREE

     This  section  is not for the novice, it describes some
of the inner workings of the configuration process  as  well
as  the  pertinent  parts  of  the  system autoconfiguration
process.  It is intended to give those people who intend  to
install  new  device  drivers and/or other system facilities
sufficient information to do so in  the  manner  which  will
allow others to easily share the changes.

     This section is broken into four parts:

+o  general  guidelines  to  be  followed in modifying system
   code,

+o  how to add non-standard system facilities to NetBSD, and

+o  how to add a device driver to NetBSD.

66..11..  MMooddiiffyyiinngg ssyysstteemm ccooddee

     If you wish to make site-specific modifications to  the
system it is best to bracket them with

     #ifdef SITENAME
     ...
     #endif

to allow your source to be easily distributed to others, and
also to simplify _d_i_f_f(1) listings.  It is  recommended  that
you save the old code with something of the form:

     #ifndef SITENAME
     ...
     #endif












Building NetBSD Kernels with ConfiCgommand Reference Documents


     Machine-specific  code  should  be  placed  in existing
machine-specific files, or added as new  files  in  machine-
specific  source  directories.   The use of machine-specific
preprocessor conditionals is discouraged.

66..22..  AAddddiinngg nnoonn--ssttaannddaarrdd ssyysstteemm ffaacciilliittiieess

     This section considers the work needed to augment  _c_o_n_-
_f_i_g's  data  base  files for non-standard system facilities.
_C_o_n_f_i_g uses a set of files that list the source modules that
may  be required when building a system.  The data bases are
taken from standard locations in  the  system  source  tree,
normally  ``/usr/src/sys/conf''.   Three  such  files may be
used: _f_i_l_e_s, _f_i_l_e_s.machine, and _f_i_l_e_s.ident.  The  first  is
common to all systems, the second contains files unique to a
single machine type, and the third is an  optional  list  of
modules  for  use on a specific machine.  This last file may
override specifications in the first two.  The format of the
_f_i_l_e_s  file  has  grown somewhat complex over time.  Entries
are normally of the form

     _d_i_r_/_s_o_u_r_c_e_._c   _t_y_p_e  _o_p_t_i_o_n_-_l_i_s_t _m_o_d_i_f_i_e_r_s

for example,

     _v_a_x_u_b_a_/_f_o_o_._c   ooppttiioonnaall  foo  ddeevviiccee--ddrriivveerr

The _t_y_p_e is one of ssttaannddaarrdd or ooppttiioonnaall.   Files  marked  as
standard   are   included   in  all  system  configurations.
Optional file specifications include a list of one  or  more
system  options  that together require the inclusion of this
module.  The options in the list  may  be  either  names  of
devices  that may be in the configuration file, or the names
of system options that may be defined.  An optional file may
be  listed  multiple times with different options; if all of
the options for any of the entries are satisfied, the module
is included.

     If  a file is specified as a _d_e_v_i_c_e_-_d_r_i_v_e_r, any special
compilation options for device drivers will be invoked.   On
the  VAX  this results in the use of the --ii option for the C
optimizer.  This is required  when  pointer  references  are
made to memory locations in the VAX I/O address space.

     Two  other  optional  keywords  modify the usage of the
file.  _C_o_n_f_i_g understands that certain files are used  espe-
cially  for  kernel profiling.  These files are indicated in
the _f_i_l_e_s files with a _p_r_o_f_i_l_i_n_g_-_r_o_u_t_i_n_e keyword.  For exam-
ple,  the  current profiling subroutines are sequestered off
in a separate file with the following entry:

     _s_y_s_/_s_u_b_r___m_c_o_u_n_t_._c   ooppttiioonnaall  pprrooffiilliinngg--rroouuttiinnee











Command Reference DocumentBsuilding NetBSD Kernels with Config


The _p_r_o_f_i_l_i_n_g_-_r_o_u_t_i_n_e keyword forces _c_o_n_f_i_g not  to  compile
the source file with the --ppgg option.

     The  second  keyword which can be of use is the _c_o_n_f_i_g_-
_d_e_p_e_n_d_e_n_t keyword.  This causes _c_o_n_f_i_g to compile the  indi-
cated module with the global configuration parameters.  This
allows certain modules, such as  _m_a_c_h_d_e_p_._c  to  size  system
data structures based on the maximum number of users config-
ured for the system.

66..33..  AAddddiinngg ddeevviiccee ddrriivveerrss ttoo NNeettBBSSDD

     The I/O system and _c_o_n_f_i_g have been designed to  easily
allow  new  device  support  to be added.  The system source
directories are organized as follows:


     /usr/src/sys/sys               machine independent include files
     /usr/src/sys/kern              machine-independent system source files
     /usr/src/sys/conf              machine-independent configuration data
     /usr/src/sys/net               network-protocol-independent, but network-related code
     /usr/src/sys/netinet           DARPA Internet code
     /usr/src/sys/dev               machine-independent device drivers
     /usr/src/sys/arch              machine-dependent code
     /usr/src/sys/arch/amd64        machine-dependent code for 64-bit x86
     /usr/src/sys/arch/i386         machine-dependent code for 32-bit x86
     /usr/src/sys/arch/x86          machine-dependent code shared between x86 types
     /usr/src/sys/arch/amd64/conf   site configuration files and basic templates
     (and so on)



     Existing block and character device drivers for the VAX
reside  in  ``/usr/src/sys/dev''.   Any  new  device drivers
should be placed in the appropriate  source  code  directory
and named so as not to conflict with existing devices.  Nor-
mally, definitions for  things  like  device  registers  are
placed  in a separate file in the same directory.  For exam-
ple, the ``auixp'' device driver is  named  ``auixp.c''  and
its  associated  include file is named ``auixpreg.h''. There
is also an ``auixpvar.h'' which contains data structures and
other external declarations that the driver needs to expose.

     Once the source for the device driver has  been  placed
in  a directory, the file ``/usr/src/sys/conf/files'' should
be modified.  The _f_i_l_e_s files in the conf directory  contain
a  line for each C source or binary-only file in the system.
Those files which are machine  independent  are  located  in
``/usr/src/sys/conf/files,''  while  machine  specific files
for       the       ``foo''        port        are        in
``/usr/src/sys/arch/foo/conf/files.foo''.                The
``devices.foo'' file is used to map device  names  to  major
block device numbers.  If the device driver being added pro-
vides support for a new disk you will want  to  modify  this









Building NetBSD Kernels with ConfiCgommand Reference Documents


file (the format is obvious).

     In  addition to including the driver in the _f_i_l_e_s file,
it must also be added to the  device  configuration  tables.
These  are  located  in  ``/sys/vax/conf.c'', or similar for
machines other than the VAX.  If you don't  understand  what
to add to this file, you should study an entry for an exist-
ing driver.  Remember that the position in the device  table
specifies  the  major device number.  The block major number
is needed in the ``devices.machine'' file if the device is a
disk.

     With  the configuration information in place, your con-
figuration file appropriately modified, and a system  recon-
figured  and  rebooted you should incorporate the shell com-
mands needed to install the special files in the file system
to  the  file  ``/dev/MAKEDEV''  or  ``/dev/MAKEDEV.local''.
This is discussed in the document ``Installing and Operating
4.4BSD''.












































Command Reference DocumentBsuilding NetBSD Kernels with Config


           AAPPPPEENNDDIIXX AA.. CCOONNFFIIGGUURRAATTIIOONN FFIILLEE GGRRAAMMMMAARR


     The  following  grammar  is  a  compressed  form of the
actual _y_a_c_c(1) grammar used by _c_o_n_f_i_g to parse configuration
files.  Terminal symbols are shown all in upper case, liter-
als are emboldened; optional clauses are enclosed in  brack-
ets,  ``[''  and  ``]'';   zero  or  more instantiations are
denoted with ``*''.

Configuration ::=  [ Spec ;; ]*

Spec ::= Config_spec
     | Device_spec
     | ttrraaccee
     | /* lambda */

/* configuration specifications */

Config_spec ::=  mmaacchhiinnee ID
     | ccppuu ID
     | ooppttiioonnss Opt_list
     | iiddeenntt ID
     | System_spec
     | ttiimmeezzoonnee [ -- ] NUMBER [ ddsstt [ NUMBER ] ]
     | ttiimmeezzoonnee [ -- ] FPNUMBER [ ddsstt [ NUMBER ] ]
     | mmaaxxuusseerrss NUMBER

/* system configuration specifications */

System_spec ::= ccoonnffiigg ID System_parameter [ System_parameter ]*

System_parameter ::=  swap_spec | root_spec | dump_spec | arg_spec

swap_spec ::=  sswwaapp [ oonn ] swap_dev [ aanndd swap_dev ]*

swap_dev ::=  dev_spec [ ssiizzee NUMBER ]

root_spec ::=  rroooott [ oonn ] dev_spec

dump_spec ::=  dduummppss [ oonn ] dev_spec

arg_spec ::=  aarrggss [ oonn ] dev_spec

dev_spec ::=  dev_name | major_minor

major_minor ::=  mmaajjoorr NUMBER mmiinnoorr NUMBER

dev_name ::=  ID [ NUMBER [ ID ] ]

/* option specifications */

Opt_list ::=  Option [ ,, Option ]*










Building NetBSD Kernels with ConfiCgommand Reference Documents


Option ::=  ID [ == Opt_value ]

Opt_value ::=  ID | NUMBER

Mkopt_list ::=  Mkoption [ ,, Mkoption ]*

Mkoption ::=  ID == Opt_value

/* device specifications */

Device_spec ::= ddeevviiccee Dev_name Dev_info Int_spec
     | mmaasstteerr Dev_name Dev_info
     | ddiisskk Dev_name Dev_info
     | ttaappee Dev_name Dev_info
     | ccoonnttrroolllleerr Dev_name Dev_info [ Int_spec ]
     | ppsseeuuddoo--ddeevviiccee Dev [ NUMBER ]

Dev_name ::=  Dev NUMBER

Dev ::=  uubbaa | mmbbaa | ID

Dev_info ::=  Con_info [ Info ]*

Con_info ::=  aatt Dev NUMBER
     | aatt nneexxuuss NUMBER

Info ::=  ccssrr NUMBER
     | ddrriivvee NUMBER
     | ssllaavvee NUMBER
     | ffllaaggss NUMBER

Int_spec ::=  vveeccttoorr ID [ ID ]*
     | pprriioorriittyy NUMBER


LLeexxiiccaall CCoonnvveennttiioonnss

The terminal symbols are loosely defined as:

ID
     One or more alphabetics, either upper  or  lower  case,
     and underscore, ``_''.

NUMBER
     Approximately the C language specification for an inte-
     ger number.  That is,  a  leading  ``0x''  indicates  a
     hexadecimal  value,  a leading ``0'' indicates an octal
     value, otherwise the number is expected to be a decimal
     value.   Hexadecimal  numbers  may  use either upper or
     lower case alphabetics.

FPNUMBER
     A floating point number without exponent.   That  is  a
     number  of  the  form ``nnn.ddd'', where the fractional









Command Reference DocumentBsuilding NetBSD Kernels with Config


     component is optional.

In special instances a question mark, ``?'', can be  substi-
tuted  for a ``NUMBER'' token.  This is used to effect wild-
carding in device interconnection specifications.

Comments in configuration files are  indicated  by  a  ``#''
character at the beginning of the line; the remainder of the
line is discarded.

A specification is interpreted as a continuation of the pre-
vious line if the first character of the line is tab.



















































Building NetBSD Kernels with ConfiCgommand Reference Documents


      AAPPPPEENNDDIIXX BB.. RRUULLEESS FFOORR DDEEFFAAUULLTTIINNGG SSYYSSTTEEMM DDEEVVIICCEESS


     When  _c_o_n_f_i_g processes a ``config'' rule which does not
fully specify the location of the root file  system,  paging
area(s),  device  for  system dumps, and device for argument
list processing it applies a set of rules  to  define  those
values  left  unspecified.   The following list of rules are
used in defaulting system devices.

1) If a root device is not specified, the swap specification
   must indicate a ``generic'' system is to be built.

2) If  the  root  device  does not specify a unit number, it
   defaults to unit 0.

3) If the root device does not include a partition  specifi-
   cation, it defaults to the ``a'' partition.

4) If  no  swap  area is specified, it defaults to the ``b''
   partition of the root device.

5) If no device is specified for processing argument  lists,
   the first swap partition is selected.

6) If  no  device is chosen for system dumps, the first swap
   partition is selected (see below to find out where  dumps
   are placed within the partition).

     The  following  table summarizes the default partitions
selected when a device  specification  is  incomplete,  e.g.
``hp0''.


     Type    Partition
     ------------------
     root    ``a''
     swap    ``b''
     args    ``b''
     dumps   ``b''



MMuullttiippllee sswwaapp//ppaaggiinngg aarreeaass

     When multiple swap partitions are specified, the system
treats the first specified as a ``primary'' swap area  which
is  always  used.   The remaining partitions are then inter-
leaved into the paging system at the time a _s_w_a_p_o_n(2) system
call  is  made.   This  is normally done at boot time with a
call to _s_w_a_p_o_n(8) from the /etc/rc file.












Command Reference DocumentBsuilding NetBSD Kernels with Config


SSyysstteemm dduummppss

     System dumps are automatically  taken  after  a  system
crash,  provided  the device driver for the ``dumps'' device
supports this.  The dump contains the  contents  of  memory,
but  not the swap areas.  Normally the dump device is a disk
in which case the information is copied to a location at the
back  of  the  partition.  The dump is placed in the back of
the partition because the primary swap and dump  device  are
commonly  the  same  device and this allows the system to be
rebooted without immediately overwriting the saved  informa-
tion.   When  a dump has occurred, the system variable _d_u_m_p_-
_s_i_z_e is set to a non-zero  value  indicating  the  size  (in
bytes) of the dump.  The _s_a_v_e_c_o_r_e(8) program then copies the
information from the dump partition to a file in a ``crash''
directory and also makes a copy of the system which was run-
ning at the time of the crash  (usually  ``/kernel'').   The
offset  to the system dump is defined in the system variable
_d_u_m_p_l_o (a sector offset from the front of  the  dump  parti-
tion).   The  _s_a_v_e_c_o_r_e  program operates by reading the con-
tents of _d_u_m_p_l_o, _d_u_m_p_d_e_v, and _d_u_m_p_m_a_g_i_c from /dev/kmem, then
comparing the value of _d_u_m_p_m_a_g_i_c read from /dev/kmem to that
located in corresponding location in the dump  area  of  the
dump  partition.   If  a  match is found, _s_a_v_e_c_o_r_e assumes a
crash occurred and reads _d_u_m_p_s_i_z_e from the dump area of  the
dump partition.  This value is then used in copying the sys-
tem dump.  Refer to _s_a_v_e_c_o_r_e(8) for more  information  about
its operation.

     The value _d_u_m_p_l_o is calculated to be

     _d_u_m_p_d_e_v_-_s_i_z_e - _m_e_m_s_i_z_e

where  _d_u_m_p_d_e_v_-_s_i_z_e  is the size of the disk partition where
system dumps are to be placed, and _m_e_m_s_i_z_e is  the  size  of
physical  memory.  If the disk partition is not large enough
to hold a full dump, _d_u_m_p_l_o is set to 0 (the  start  of  the
partition).

























Building NetBSD Kernels with ConfiCgommand Reference Documents


           AAPPPPEENNDDIIXX CC.. SSAAMMPPLLEE CCOONNFFIIGGUURRAATTIIOONN FFIILLEESS


     The following configuration files are developed in sec-
tion 5; they are included here for completeness.


#
# ANSEL VAX (a picture perfect machine)
#
machine        vax
cpu            VAX780
timezone       8 dst
ident          ANSEL
maxusers       40

config         kernel    root on hp0
config         hpkernel  root on hp0 swap on hp0 and hp2
config         genkernel swap generic

controller     mba0      at nexus ?
disk           hp0       at mba? disk ?
disk           hp1       at mba? disk ?
controller     mba1      at nexus ?
disk           hp2       at mba? disk ?
disk           hp3       at mba? disk ?
controller     uba0      at nexus ?
controller     tm0       at uba? csr 0172520vector tmintr
tape           te0       at tm0 drive 0
tape           te1       at tm0 drive 1
device         dh0       at uba? csr 0160020vector dhrint dhxint
device         dm0       at uba? csr 0170500vector dmintr
device         dh1       at uba? csr 0160040vector dhrint dhxint
device         dh2       at uba? csr 0160060vector dhrint dhxint





























Command Reference DocumentBsuilding NetBSD Kernels with Config


#
# UCBVAX - Gateway to the world
#
machine        vax
cpu            "VAX780"
cpu            "VAX750"
ident          UCBVAX
timezone       8 dst
maxusers       32
options        INET
options        NS

config         kernel    root on hp swap on hp and rk0 and rk1
config         upkernel  root on up
config         hkkernel  root on hk swap on rk0 and rk1

controller     mba0      at nexus ?
controller     uba0      at nexus ?
disk           hp0       at mba? drive 0
disk           hp1       at mba? drive 1
controller     sc0       at uba? csr 0176700vector upintr
disk           up0       at sc0 drive 0
disk           up1       at sc0 drive 1
controller     hk0       at uba? csr 0177440vector rkintr
disk           rk0       at hk0 drive 0
disk           rk1       at hk0 drive 1
pseudo-device  pty
pseudo-device  loop
pseudo-device  imp
device         acc0      at uba? csr 0167600vector accrint accxint
pseudo-device  ether
device         ec0       at uba? csr 0164330vector ecrint eccollide ecxint
device         il0       at uba? csr 0164000vector ilrint ilcint






























Building NetBSD Kernels with ConfiCgommand Reference Documents


     AAPPPPEENNDDIIXX DD.. VVAAXX KKEERRNNEELL DDAATTAA SSTTRRUUCCTTUURREE SSIIZZIINNGG RRUULLEESS


     Certain system data structures  are  sized  at  compile
time  according  to the maximum number of simultaneous users
expected, while others are calculated at boot time based  on
the  physical resources present, e.g. memory.  This appendix
lists both sets of rules and also  includes  some  hints  on
changing built-in limitations on certain data structures.

CCoommppiillee ttiimmee rruulleess

     The  file _/_s_y_s_/_c_o_n_f_/_p_a_r_a_m_._c contains the definitions of
almost all data structures sized at compile time.  This file
is  copied  into  the directory of each configured system to
allow configuration-dependent rules and values to  be  main-
tained.    (Each  copy  normally  depends  on  the  copy  in
/sys/conf, and global modifications cause  the  file  to  be
recopied  unless  the  makefile  is  modified.)   The  rules
implied by its contents are summarized below (here  MAXUSERS
refers to the value defined in the configuration file in the
``maxusers'' rule).  Most limits  are  computed  at  compile
time  and  stored  in global variables for use by other mod-
ules; they may generally be patched  in  the  system  binary
image before rebooting to test new values.

nnpprroocc
     The maximum number of processes which may be running at
     any time.  It is referred to in other  calculations  as
     NPROC and is defined to be

          20 + 8 * MAXUSERS


nntteexxtt
     The maximum number of active shared text segments.  The
     constant is intended to allow for network  servers  and
     common  commands  that  remain  in  the  table.   It is
     defined as

          36 + MAXUSERS.


nniinnooddee
     The maximum number of files in the  file  system  which
     may  be active at any time.  This includes files in use
     by users, as well as  directory  files  being  read  or
     written  by  the system and files associated with bound
     sockets in the UNIX IPC domain.  It is defined as

          (NPROC + 16 + MAXUSERS) + 32












Command Reference DocumentBsuilding NetBSD Kernels with Config


nnffiillee
     The number of ``file table'' structures.  One file  ta-
     ble  structure  is  used  for each open, unshared, file
     descriptor.  Multiple file descriptors may reference  a
     single file table entry when they are created through a
     _d_u_p call, or as the result of a _f_o_r_k.  This is  defined
     to be

          16 * (NPROC + 16 + MAXUSERS) / 10 + 32


nnccaalllloouutt
     The  number  of  ``callout''  structures.   One callout
     structure is used per  internal  system  event  handled
     with a timeout.  Timeouts are used for terminal delays,
     watchdog routines in device drivers,  protocol  timeout
     processing, etc.  This is defined as

          16 + NPROC


nncclliisstt
     The number of ``c-list'' structures.  C-list structures
     are used in terminal I/O, and currently each  holds  60
     characters.  Their number is defined as

          60 + 12 * MAXUSERS


nnmmbbcclluusstteerrss
     The  maximum  number of pages which may be allocated by
     the  network.   This  is  defined  as  256  (a  quarter
     megabyte of memory) in /sys/h/mbuf.h.  In practice, the
     network rarely uses this much memory.  It starts off by
     allocating  8 kilobytes of memory, then requesting more
     as required.  This value represents an upper bound.

nnqquuoottaa
     The number of ``quota''  structures  allocated.   Quota
     structures  are  present only when disc quotas are con-
     figured in the system.  One quota structure is kept per
     user.  This is defined to be

          (MAXUSERS * 9) / 7 + 3


nnddqquuoott
     The  number  of  ``dquot'' structures allocated.  Dquot
     structures are present only when disc quotas  are  con-
     figured in the system.  One dquot structure is required
     per user, per active file system quota.  That is,  when
     a  user  manipulates  a  file on a file system on which
     quotas  are  enabled,  the  information  regarding  the
     user's  quotas  on  that  file  system must be in-core.









Building NetBSD Kernels with ConfiCgommand Reference Documents


     This information is cached, so that not all information
     must  be present in-core all the time.  This is defined
     as

          NINODE + (MAXUSERS * NMOUNT) / 4

     where NMOUNT is the maximum number  of  mountable  file
     systems.

In  addition  to  the  above  values, the system page tables
(used to map virtual memory in the kernel's  address  space)
are sized at compile time by the SYSPTSIZE definition in the
file /sys/vax/vmparam.h.  This is defined to be

     20 + MAXUSERS

pages of page tables.  Its definition affects  the  size  of
many  data structures allocated at boot time because it con-
strains the amount of virtual memory which may be  addressed
by the running system.  This is often the limiting factor in
the size of the buffer cache, in which  case  a  message  is
printed when the system configures at boot time.

RRuunn--ttiimmee ccaallccuullaattiioonnss

     The  most  important  data structures sized at run-time
are those used in the buffer cache.  Allocation is  done  by
allocating physical memory (and system virtual memory) imme-
diately after the system has been started up;  look  in  the
file  /sys/vax/machdep.c.   The  amount  of  physical memory
which may be allocated to the buffer cache is constrained by
the  size  of  the  system  page tables, among other things.
While the system may calculate a large amount of  memory  to
be  allocated  to the buffer cache, if the system page table
is too small to map this physical memory  into  the  virtual
address  space  of the system, only as much as can be mapped
will be used.

     The buffer cache is comprised of a number  of  ``buffer
headers''  and  a  pool  of pages attached to these headers.
Buffer headers are divided into two categories:  those  used
for swapping and paging, and those used for normal file I/O.
The system tries to allocate 10% of the first two  megabytes
and  5%  of  the remaining available physical memory for the
buffer cache (where _a_v_a_i_l_a_b_l_e  does  not  count  that  space
occupied  by  the system's text and data segments).  If this
results in fewer than 16 pages of memory allocated, then  16
pages  are allocated.  This value is kept in the initialized
variable _b_u_f_p_a_g_e_s so that it may be patched  in  the  binary
image  (to  allow tuning without recompiling the system), or
the default may  be  overridden  with  a  configuration-file
option.   For  example,  the  option ooppttiioonnss BBUUFFPPAAGGEESS==""33220000""
causes 3200 pages (3.2M bytes) to  be  used  by  the  buffer
cache.   A  sufficient number of file I/O buffer headers are









Command Reference DocumentBsuilding NetBSD Kernels with Config


then allocated to allow each to hold  2  pages  each.   Each
buffer  maps  8K  bytes.   If  the number of buffer pages is
larger than can be mapped by the buffer headers, the  number
of pages is reduced.  The number of buffer headers allocated
is stored in the global variable _n_b_u_f, which may be  patched
before  the  system  is  booted.   The system option ooppttiioonnss
NNBBUUFF==""11000000"" forces the allocation of  1000  buffer  headers.
Half as many swap I/O buffer headers as file I/O buffers are
allocated, but no more than 256.

SSyysstteemm ssiizzee lliimmiittaattiioonnss

     As distributed, the sum of the  virtual  sizes  of  the
core-resident  processes is limited to 256M bytes.  The size
of the text segment of a single process is currently limited
to  6M  bytes.   It  may be increased to no greater than the
data segment size limit (see below) by  redefining  MAXTSIZ.
This  may  be  done  with  a configuration file option, e.g.
ooppttiioonnss MMAAXXTTSSIIZZ==""((1100**11002244**11002244))"" to set the limit to 10 mil-
lion  bytes.  Other per-process limits discussed here may be
changed with similar options with names given  in  parenthe-
ses.  Soft, user-changeable limits are set to 512K bytes for
stack (DFLSSIZ) and 6M bytes for the data segment  (DFLDSIZ)
by default; these may be increased up to the hard limit with
the _s_e_t_r_l_i_m_i_t(2) system call.  The data  and  stack  segment
size hard limits are set by a system configuration option to
one of 17M, 33M or 64M bytes.  One of these sizes is  chosen
based  on  the  definition  of  MAXDSIZ; with no option, the
limit  is  17M  bytes;  with   an   option   ooppttiioonnss   MMAAXXDD--
SSIIZZ==""((3322**11002244**11002244))"" (or any value between 17M and 33M), the
limit is increased to 33M bytes, and values larger than  33M
result  in  a  limit  of  64M bytes.  You must be careful in
doing this that you have adequate paging space.  As normally
configured  ,  the  system  has  16M or 32M bytes per paging
area, depending on disk size.  The  best  way  to  get  more
space  is  to  provide multiple, thereby interleaved, paging
areas.  Increasing the  virtual  memory  limits  results  in
interleaving  of  swap  space  in larger sections (from 500K
bytes to 1M or 2M bytes).

     By default, the virtual memory system allocates  enough
memory  for  system  page tables mapping user page tables to
allow 256 megabytes of simultaneous active  virtual  memory.
That  is,  the  sum of the virtual memory sizes of all (com-
pletely- or partially-) resident processes  can  not  exceed
this limit.  If the limit is exceeded, some process(es) must
be swapped out.  To increase the amount of resident  virtual
space  possible,  you  can  alter the constant USRPTSIZE (in
/sys/vax/vmparam.h).  Each page of system page tables allows
8 megabytes of user virtual memory.

     Because  the  file  system  block numbers are stored in
page table _p_g___b_l_k_n_o entries, the maximum size of a file sys-
tem  is  limited  to  2^24  1024  byte blocks.  Thus no file









Building NetBSD Kernels with ConfiCgommand Reference Documents


system can be larger than 8 gigabytes.

     The number of mountable file systems is set  at  20  by
the  definition of NMOUNT in /sys/h/param.h.  This should be
sufficient; if not, the value can be increased  up  to  255.
If  you have many disks, it makes sense to make some of them
single file systems, and the paging  areas  don't  count  in
this total.

     The  limit  to  the  number of files that a process may
have open simultaneously is set to 64.  This limit is set by
the   NOFILE   definition  in  /sys/h/param.h.   It  may  be
increased arbitrarily, with the caveat that the user  struc-
ture  expands  by  5  bytes  for  each file, and thus UPAGES
(/sys/vax/machparam.h) must be increased accordingly.

     The amount of physical memory is currently  limited  to
64  Mb  by  the  size  of  the  index fields in the core-map
(/sys/h/cmap.h).  The limit may be  increased  by  following
instructions in that file to enlarge those fields.











































Command Reference DocumentBsuilding NetBSD Kernels with Config


         AAPPPPEENNDDIIXX EE.. NNEETTWWOORRKK CCOONNFFIIGGUURRAATTIIOONN OOPPTTIIOONNSS


     The  network  support in the kernel is self-configuring
according to the protocol support options (INET and NS)  and
the  network  hardware  discovered during autoconfiguration.
There are several changes that may be made to customize net-
work  behavior due to local restrictions.  Within the Inter-
net protocol routines, the following options set in the sys-
tem configuration file are supported:

GGAATTEEWWAAYY
     The  machine  is  to be used as a gateway.  This option
     currently makes only minor changes.  First, the size of
     the network routing hash table is increased.  Secondly,
     machines that  have  only  a  single  hardware  network
     interface  will  not  forward  IP packets; without this
     option, they will also refrain from sending  any  error
     indication  to  the  source  of  unforwardable packets.
     Gateways with only a single interface  are  assumed  to
     have missing or broken interfaces, and will return ICMP
     unreachable errors to hosts sending them packets to  be
     forwarded.

TTCCPP__CCOOMMPPAATT__4422
     This  option forces the system to limit its initial TCP
     sequence numbers to  positive  numbers.   Without  this
     option,  4.4BSD systems may have problems with TCP con-
     nections to  4.2BSD  systems  that  connect  but  never
     transfer data.  The problem is a bug in the 4.2BSD TCP.

IIPPFFOORRWWAARRDDIINNGG
     Normally, 4.4BSD machines with multiple network  inter-
     faces  will  forward IP packets received that should be
     resent to another host.  If the line  ``options  IPFOR-
     WARDING="0"''  is  in the system configuration file, IP
     packet forwarding will be disabled.

IIPPSSEENNDDRREEDDIIRREECCTTSS
     When forwarding IP packets, 4.4BSD IP will note when  a
     packet  is  forwarded using the same interface on which
     it arrived.  When this is noted, if the source  machine
     is  on  the directly-attached network, an ICMP redirect
     is sent to the source host.  If  the  packet  was  for-
     warded  using  a route to a host or to a subnet, a host
     redirect is sent, otherwise a network redirect is sent.
     The  generation  of redirects may be inhibited with the
     configuration option ``options IPSENDREDIRECTS="0".''

SSUUBBNNEETTSSAARREELLOOCCAALL
     TCP calculates a maximum segment size to use  for  each
     connection,  and  sends  no  datagrams larger than that
     size.  This size will be no larger than that  supported
     on   the   outgoing  interface.   Furthermore,  if  the









Building NetBSD Kernels with ConfiCgommand Reference Documents


     destination is not on the local network, the size  will
     be no larger than 576 bytes.  For this test, other sub-
     nets of a directly-connected subnetted network are con-
     sidered  to  be local unless the line ``options SUBNET-
     SARELOCAL="0"'' is used  in  the  system  configuration
     file.

The  following  options are supported by the Xerox NS proto-
cols:

NNSSIIPP
     This option allows NS IDP datagrams to be  encapsulated
     in  Internet  IP packets for transmission to a collabo-
     rating NSIP host.  This may be used to pass IDP packets
     through  IP-only link layer networks.  See _n_s_i_p(4P) for
     details.

TTHHRREEEEWWAAYYSSHHAAKKEE
     The NS Sequenced Packet Protocol  does  not  require  a
     three-way  handshake before considering a connection to
     be in the established state.   (A  three-way  handshake
     consists of a connection request, an acknowledgement of
     the request along with a  symmetrical  opening  indica-
     tion,  and  then  an  acknowledgement of the reciprocal
     opening packet.)  This option forces a three-way  hand-
     shake  before  data  may  be  transmitted  on Sequenced
     Packet sockets.

































