Bug fixes and changes in 4.1bsd
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This is the note included with 4.1 BSD
Bug fixes and changes in 4.1bsd
May 10, 1981
Bill Joy
Computer Systems Research Group
ABSTRACT
This document describes briefly the changes
in the Berkeley system for the VAX between the
fourth distribution of November 1980 (known origi-
nally as 4BSD, and hereinafter referred to as
4.0bsd) and this, its revision of April 1981. It
attempts to be summarize, without going into great
detail, the changes which have been made.
Notable improvements
+ Performance of the system under heavy paging load has
been substantially improved by correcting a problem
with placement of pre-paged pages. The system now
pre-pages more data, greatly benefitting processes
which have locality in their behavior. System degrada-
tion due to pre-paging has been reduced (even though
more pre-paging is done), by placing the pre-paged
pages as the bottom of the free-list, rather than in
the systems global clock replacement loop.
+ Processes which serially reference large amounts of
virtual memory may now declare themselves to be sequen-
tial (see vadvise(2)), causing the paging algorithm to
be adjusted to be more appropriate for such behavior.*
Processes which are known to need only a small amount
of memory, but which tend to accumulate large amounts
of memory due to strange page referencing patterns may
declare a soft limit on the amount of memory to be
used, see vlimit(2) or do ``limit memoryuse nk'' in
csh(1). If the system needs memory, and there are
processes which are over their declared limits, the
__________________________
* Future versions of the system will detect strongly
sequential behavior and adapt themselves accordingly,
so this call will no longer be necessary.
July 14, 1981
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system tends to take pages from these processes first.
By saying that these limits are soft, we mean that on a
system where physical memory is not scarce, processes
with limits can still acquire as much physical memory
as they require.
+ The system is now compiled from a description of the
local machine which includes information about avail-
able devices and the maximum number of users to be sup-
ported on the system. It is no longer necessary to
adjust an armful of constants to re-size the system;
normal time-sharing systems are parameterized from a
single ``maxusers'' constant. The system also adjusts
the parameters of the paging subsystem based on avail-
able memory; it is no longer necessary to adjust these
for machines with very small or very large amounts of
available memory.
+ The system now handles multiple uba's and mba's and
mixing of devices on mba's. A number of new devices
are supported: RK07's and TS-11's which come in the
standard 11/750 packages, UNIBUS TM-11 tape emulators
(e.g. the EMULEX TC-11 with a KENNEDY 9300 transport).
Line printer and C/A/T phototypesetter drivers are
included in the system, and modem control for the DH-11
using the DM-11 has been integrated and tested. The
new RM-80 Winchester drive from DEC is supported. Not-
ably unsupported are the 11/750 console casettes. A
single distribution system boots on all supported
hardware configurations by determining the available
devices and selecting a root device at boot time.
+ The tar program has been changed to allow update of
magnetic tape archives, adding to the end of the exist-
ing tape archive. This uses tape control facilities
newly added in this version of the system, but the
created tapes are readable on all versions of UNIX.
Since blocked tapes are inherently more efficient and
fully functional, tar now creates blocked tapes by
default.
+ Shell scripts are now potentially executable. A file
which begins with the characters ``#!'' followed by
some amount of white space and the name of an inter-
preter is executed directly by the system. The stan-
dard version 7 shell, /bin/sh, has been changed to
recognize a # as a comment character. It is desirable
that users change existing shell script so that the
first line of each shell script begins with ``#!'' and
the name of the proper shell to execute.
+ Two new documents have been added to Volume 2c: a
manual for the crt screen package -lcurses, and a docu-
ment describing the rogue game.
July 14, 1981
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Major bug fixes
+ A number of bugs have been fixed in the FORTRAN com-
piler F77; these caused some block data routiens and
main programs to fail to compile. Other bugs related
to use of the symbolic debugger with FORTRAN have been
fixed (see f77 in ``Section 1'' below.)
+ A bug which caused the C compiler to complain ``expres-
sion too complicated'' when an expression contained an
embedded structure assignment has been fixed.
+ A kernel bug which caused approximately 1/8'th of data
collected during program profiling to be lost has been
corrected.
+ A very confusing bug in the tset manual page has been
corrected: in the example where it uses the setenv com-
mand it should rather use the set command: ``set
noglob; eval ...''. The alternate form does not work
on a number of terminals.
+ Due to a inconsistency between the 11/780 and the 11/750
in the interpretation of the movtuc instruction, all
binaries from the third distribution tape (of January
1980) and the fourth distribution tape (of November
1980) will NOT run correctly on the 11/750. The 4.1bsd
distribution tape includes a new version of the standard
i/o library which avoids use of this troublesome
instruction, and it is recommended that all programs be
recompiled from scratch to use this new library to elim-
inate non-portable UNIX binaries as soon as possible.
The problem is that when there appears to be a chance
that the operands to movtuc will overlap, but they in
fact do not (because the pattern string to printf is
terminated by a null), the 11/750 does not execute the
movtuc as though a shorter string length were specified
which did not imply potential overlap. Thus this
instruction which is in the inner loop of printf on the
4bsd tape, and which works fine on an 11/780, malfunc-
tions on an 11/750 causing strange and awful behavior.
+ (The following change is applicable only to systems
bootstrapped from the 4.1bsd release tape; systems
upgraded from 4.0bsd may or may not include this
change.) The standard i/o library has been made more
compatible with the PDP-11 version 7 system and now sup-
ports concurrent read and write access to files (see
fopen(3s) for details). This caused a change in an
internal data structure which is visible to compiled
programs through the macros in , and thus
necessitates discarding of old .o files and
July 14, 1981
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recompilation. Note that this standard i/o library now
replaces the old -lNS library which was in 3bsd but was
deleted from 4bsd pending the inclusion of read-write
capability in stdio.
Section 1
adb A bug which prevented programs loaded with the -N
loader option from having breakpoints set on them
has been fixed. A bug which prevented backtraces
of programs which are stopped at interrupt level
(after a signal) has been fixed by teaching adb
how to step across the interrupt stack frame.
The system now makes available and the $? command
in adb interprets more precise codes when SIGILL
and SIGFPE exceptions occur. Thus if you divide
by zero, you can find out that this was what
caused a floating point exception. A bug which
prevented format repetition counts (e.g. the 10
in ``0/10X'') from working has been fixed. A bug
related to adb has been fixed that prevented any
sensible traceback after a FORTRAN-77 runtime
error which trapped an exception or fault (e.g. a
floating point divide by 0). A bug which caused
the maps to be set improperly when debugging the
kernel on a crash dump has been fixed.
New commands have been added to adb to facilitate
writing adb procedures stored in files: see the
descriptions of $<<, the register <9, and the #
operator in the revised adb manual page.
awk Has moved from /usr/bin to /bin because it is
needed during bootstrap procedures.
bc Now takes the new C syntax operators: ``=op'' as
well as (for history's sake) the old syntax
``op=''.
calendar Several bugs have been fixed in the internals of
the calendar program. In addition it is now pos-
sible to have a calendar entry consisting of
merely a date (with no month specified) and have
this entry occur each month.
cc A bug has been fixed in the C optimizer which
caused strange things to happen when long vari-
able names were used. The size of the internal
``dimension'' table has been increased to allow
more structure fields to be declared. A problem
which caused the compiler to print ``expression
causes compiler loop'' when structure assignment
July 14, 1981
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was embedded in an expression context has been
fixed. A bug in the code generator tables which
affected certain FORTRAN constructs has also been
fixed.
checknr Es versteht -mm.
csh A cosmetic bug which prevented the distributed
source from compiling has been fixed. A bug
which caused argument lists including the strings
``{'' or ``{}'' to sometimes fail saying ``No
match'' has been fixed. A bug which caused a
strange state to result when a command of the
form ``(a; b; c)'' was stopped from the keyboard
has been fixed. The shell has been fixed so that
it prefers to make stopped jobs the new current
jobs after the current job has terminated. The
construct ``${TERM}'' no longer yields an extra
``}'' when the variable expanded is from the
environment.
Previously undocumented was the shell variable
histchars; it can be set to two characters, and
the first is then a replacement for the normal !
history character and the second for the ^ quick
history substitution character. Thus after ``set
histchars=,;'' the command ``,,'' repeats the
previous command, as ``!!'' would normally have
done.
ctags Now takes an option -v to produce output suitable
for input to vgrind(1).
cu Now honors uucp's locking protocol for the
dialout lines. Several bugs relating to internal
buffer overruns have been fixed. An option -b
has been added which causes the BREAK key to gen-
erate breaks (by turning input null characters
into breaks sent over the line).
delivermail
Some bugs which caused strange loops when aliases
were self-referential have been fixed.
diff Some bugs related to directory diffs when the -h
option was used have been fixed; previously the
-h option was non-functional.
dump An obnoxious bug in the dump program where it
would wrongly suggest that further dump tapes
were needed after a multi-tape dump had already
completed has been fixed. The dump program no
longer attempts to time tape rewinds itself, but
uses a mechanism which does not depend on the
July 14, 1981
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speed of the tape drive to determine when a
rewind is complete.
error Has been taught about the error message formats
of the PDP-11 C compiler.
expand A internal error check which was incorrect has
been fixed.
f77 Has had a bug fixed which caused some block data
subroutines and main programs to not compile (the
sympton was a diagnostic of the form ``Undefined:
LWM%d''. A number of minor bugs which combined
to make sdb function poorly with f77 have been
fixed. The result of these bugs were that if
file names were longer than 6 characters sdb
could not read the symbol table of the resulting
FORTRAN binary.
An i/o library bug which caused numbers of the
form ``-1.2'' to convert improperly in list-
directed input (reading as ``-0.8'', taking the
mantissa as positive) has been fixed.
ld If you are using the -r flag and there remain
undefined symbols you no longer get a spurious
error return. Now respects modes of existing
files and your file-creation mask more.
lisp The functions +, /, -, *, 1+, 1- now expect fix-
num arguments, for interpreted functons as well
as compiled ones. The source for the VMS and
UNIX versions of lisp have been combined and syn-
chronized. The construction of very large
integers has been altered to use regular dotted
pairs in a non-standard way, so that fewer gar-
bage collections will occur. (It is no longer
safe to use ``car'' and ``cdr'' to disect large
integers). Mixed-mode arithmetic has been made
faster. There is a new compiler option (liszt
-r) which allows you to create small lisp appli-
cation programs (with a mechanism other than
``dumplisp'', which tends to create very large
binaries). When the result of such a compilation
is executed directly, it execs /usr/ucb/lisp and
then fast loads the file you asked to be exe-
cuted. A new flag $ldprint has been added to
control the printing of fasl/load messages. New
functions (purecopy), (getdata), (putdata), and
(removeaddress) have been added. A number of
minor bugs have been fixed.
July 14, 1981
- 7 -
lpr Has been modified to work on both DECWRITER type
devices at 1200 baud masquerading as printers and
also on real line printers. The queueing algo-
rithm has been made first-come-first-serve
(replacing the old random job first algorithm),
and a line printer driver is now available in the
standard distributed system.
ls A bug has been fixed which caused essentially
random numbers to be printed for the size of spe-
cial files. The size now prints as 0.
make A spelling error has been fixed which had the
variable EC initialized to f77 rather than
FC=f77.
man A bug which caused it to core dump when reformat-
ting a manual page whose source macros were inac-
cessible has been fixed.
mt Is a new command which provides easy access to
operations such as forward and backward spacing
of files and records on magnetic tape.
mv Has been changed to have a option ``-'' which
means that all the following arguments are file
names. A bug has been fixed which caused strange
behaviour when the -i option was used on direc-
tories. A bug which prevented renaming of sub-
directories to which you had no write access has
been fixed.
oldcsh Which was non-functional due to a change in a
internal library interface which it had taken
advantage of has been fixed to work.
od New options O, X, and D print 32 bit integers in
octal hex and decimal format; an option w has
been added to cause 132 column output rather than
the default 80 column oriented output.
pc/pi A number of bugs in the sdb symbol table produced
have been fixed. Structured types may now exceed
65k bytes in size, but in that case may not be
passed by value nor assigned by simple assign-
ment. Structured types are properly returned
from recursive functions. Minor bugs in passing
function parameters have been fixed, and there
still exist some more minor bugs here. Runtime
tests can be now be enabled or disabled on a per
routine basis. Runtime checks are now done prop-
erly on builtin functions. Warnings (or stan-
dards violations) are now produced for extensions
to the language. Some inconsistencies in dealing
July 14, 1981
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with running out of memory have been fixed.
Some bugs are known: invoking a formal routine
from inside a formal invocation of the same rou-
tine will mess up. In pc only: linking
seperately compiled modules from other than the
current directory only works if you give full
path names (or the same relative paths) for the
compilation and the linking.
Some changes are planned soon: for-loop variables
and with pointers will be allocated to registers.
The formal routine syntax is currently as in Jen-
sen and Wirth, but will soon be changed to the
the syntax of the proposed standards, in which
parameters to formals must be given. It is
planned that pc will soon do compile time con-
stant folding.
pmerge Is a new program which can convert large Pascal
programs back into a single file, eliminating the
header files and separate source files normally
used for separate compilation.
prof A bug which caused prof to loop when a file-
static function was profiled has been fixed. A
bug in the kernel which caused the results of
prof to be inaccurate has also been fixed.
ps Has been changed to work with the new kernel and
is no longer dependent on system sizing; thus it
is no longer necessary to recompile ps when the
system tables are made larger. A bug in the s
option which caused the computed stack size to be
a constant 512 bytes too large has been fixed.
The ``STAT'' field now shows ``>'' in the second
position for programs which are using more memory
than their memoryuse limit (see vlimit(2)). It
also shows ``S'' in the fourth position for
processes which have declared themselves to be
strongly sequential (see vadvise(2)). Under the
v option, the SWRSS field has been replaced by a
new field ``LIM'' which shows the limit on memor-
yuse if there is a limit, or xx if there is not.
px Is now written in C, is much more portable, and
shares the runtime library used by the compiler.
It is, unfortunately, somewhat slower now.
ranlib No longer considers it a fatal error that an
archive member defines no symbols.
July 14, 1981
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reset Has been changed to invoke the command
tset -Q -I
so that all terminal modes will be reset.
rm Now has a - option to indicate that all the fol-
lowing parameters are to be treated as file
names. It can be used when file names begin with
``-''.
rmdir Now works correctly when arguments end in one or
more ``/'' characters.
sdb Has been fixed to be able to deal with
``interrupt-stack-frames'', so that it is possi-
ble to set breakpoints on and get backtraces from
routines called while a signal is being pro-
cessed. Now handles binaries which are mode 0407
(resulting from ``ld -N'') properly.
sh Has been changed so that ``#'' begins a comment.
Shell scripts to be executed by /bin/sh should
begin ``#! /bin/sh'' on the first line.
tar Now defaults to blocked tape and can update
blocked tapes (finally!). When reading tape tar
defaults to the raw tape and figures out what is
going on with blocksize so it need not be speci-
fied. Thus the only commands which should be
needed are the simple ``tar t'', ``tar c'', ``tar
u'' and ``tar x''.
uusend Now uses the -r option of uux to prevent present-
ing extreme load to the connected system.
vmstat Has been changed so that the system's device
names are printed for the disks rather than D0,
D1, D2, D3. The old format output of the -i
option is no longer available.
The fields related to paging activity are now all
given in pages (of 1024 bytes). In particular,
the fields ``pi'' and ``po'' which previously
showed the number of pagein and pageout events
now show pages, and ``sr'' which previously gave
the clock scan rate in revolutions-per-minute now
gives the scan rate in pages scanned per second.
To provide the extra space needed to present this
information, the swap in/out information, which
was only marginally interesting, is no longer
printed.
July 14, 1981
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w Has been modified so that it no longer needs to
be recompiled when the kernel tables change in
size.
wall Now checks that the message is not too long for
its internal buffer, rather than just overrunning
the buffer. It handles running out of processes
by pausing, so it is possible to use it when
there are more than 25 users logged in and you
are not the super-user. It also gives the
machine name you are on in the broadcast mes-
sages.
who ``Who am I'' now prints your machine and login
name (the first word of its output) in a format
suitable for use with uucp.
write Now checks that you do not have write permission
disabled and doesn't let you write to someone if
they can't write back.
Section 2.
intro Now correctly reflects that argument lists may be
upto 10240 characters long.
exec Has been changed so that if a file being executed
begins with the magic characters #!, the rest of
the line is understood to be the name of an
interpreter for the executed file. Previously
(and in fact still) the shell did much of this
job; it automatically executed itself on a text
file with executable mode when the text file's
name was typed as a command. Putting the facil-
ity into the system gives the following benefits.
1) It makes shell scripts more like real exe-
cutable files, because they can be the sub-
ject of 'exec.'
2) If you do a 'ps' while such a command is
running, its real name appears instead of
'sh'. Likewise, accounting is done on the
basis of the real name.
3) Shell scripts can be set-user-ID.
4) It is simpler to have alternate shells
available; e.g. if you like the Berkeley csh
there is no question about which shell is to
interpret a file.
July 14, 1981
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5) It will allow other interpreters to fit in
more smoothly.
To take advantage of this wonderful opportunity,
put
#! /bin/sh
at the left margin of the first line of your
shell scripts. Blanks after ! are OK. Use a
complete pathname (no search is done). At the
moment the whole line is restricted to 32 charac-
ters. A single argument may be specified for the
interpreter, thus:
#! /bin/csh -f
is very useful, avoiding reading .cshrc which is
often not wanted.
kill Has been changed so that when broadcasting sig-
nals universally the signal being broadcast is
not sent to the broadcaster. This is used by the
halt(8), shutdown(8), and reboot(8) commands.
reboot Has been changed to reflect the now more limited
number of option flags available to the system
call due to the nature of the console interface
on the VAX 11/750.
sigsys Reflects the fact that the system now passes in
to a signal handler an indication of what excep-
tion really happened when a SIGFPE or SIGILL is
generated. The call interface at the point of a
signal handler call is now specified.
Section 3
curses A large number of bug fixes have been incor-
porated, and the documentation has been greatly
improved. The library is now much more solid
than that originally distributed.
fopen Reflects the new open options which allow simul-
taneous read-write to files; these extensions are
being incorporated to bring compatibility with
the standard version 7 PDP-11 UNIX and to replace
the (now defunct) -lNS.
July 14, 1981
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printf A bug in the documentation which incorrectly
stated that a %c format would not put out a null
character has been fixed.
Section 4
The system now supports a number of new devices and has
capability for detecting the device's presence and interrupt
vectors at boot time. The system also has capability to do
device location at boot time so that a system description as
supplied to config(8) can take advantage of available
hardware redundancy.
Each configurable device driver in this section now
includes a SYNOPSIS giving sample lines to be included in a
system configuration. Drivers also indicate the error mes-
sages which they produce and describe each error.
ct A driver for a C/A/T phototypesetter interface.
dh Now includes handling of dm-11 modem control
hardware. Optional flags to the configuration
program can also be given to supply hardware car-
rier easily for lines where wiring is inadequate.
hp Includes rm80 support.
lp Drives standard line printers, and has been
improved to cut the interrupt load by a factor of
20.
mt Describes the standard tape drive interface,
which now includes ioctl operations for raw
magtape allowing such standard operations as for-
ward and backward spacing over files and records,
writing of end-of-file marks, rewinds, rewinding
and offlining, and sensing of tape status. These
operations are used by the mt(1) program which
can be used to easily manipulate tape files, and
by the tar(1) program to allow updates to blocked
tapes.
tm Supports the UNIBUS TM/11 emulating tape con-
trollers (e.g. EMULEX TC-11 with a KENNEDY 9300
drive).
ts Supports the UNIBUS TS/11 tape drive and tran-
sport.
tty Now provides a LDECCTLQ option which causes ^S
and ^Q to function as necessary for the VT100 to
work properly.
July 14, 1981
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up A driver for a EMULEX SC-11 or SC-21 UNIBUS disk
controller with storage module (e.g. Ampex 9300)
disk drives.
va A varian raster plotter.
Section 5
No changes.
Section 6
chase Is a game where robots try to eat you.
hangman Is now screen oriented.
rain Drops keep falling on my head.
rogue Is a new and very popular screen-oriented game,
see rogue(6) or ``A Guide to the Dungeons of
Doom.''
worm Is a game where you see how long you can get the
worm to grow.
worms Is an amusement where the worms chase each other
around the screen.
Section 7
No changes.
Section 8
Major changes affecting system operations include:
* The system is configured from a single per-cpu specifi-
cation file which includes all locally relevant infor-
mation: desired devices, size of the maximum user load,
timezone information, etc. The system determines at
boot time the size of the file system buffer cache
based on the amount of physical memory available and
sizes the system data structures based on the specifi-
cation of the maximum number of active users; it is no
longer necessary to juggle an armful of constants to
enlarge the system. The sizes of system tables are no
longer compiled into programs such as ps and w.
* System error log information is saved across system
crashes provided no power failure occurs, as the error
log is kept in-core in the last 1024 bytes of memory.
Error messages to the console are in a standard format,
July 14, 1981
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of the form:
device: message
Messages have error registers decoded as bits, so that
they are readable, and no-longer refer to devices by
their major/minor device numbers, rather using device
names. Error messages about file system problems (dev-
ice full, out of inodes, etc) are referred to with the
mounted file system name, and a message is sent
directly to a user if his/her process writes to a file
system when it is full. All error diagnostics printed
by drivers are documented in section 4 of the manual.
* DEC standard bad block forwarding is supported on all
DEC disks except the RP06; the code which implements
this can be easily moved into the drivers for the
UNIBUS storage module disks; this is planned.
* Core dumps are saved after system crashes automatically
as the system writes a core image to a portion of the
swap area from which it is recovered after reboot. The
system then transfers these core images to a specified
UNIX directory, saving also the version of the system
associated with the crash. The system also maintains
an error log /usr/adm/shutdownlog which records all
system crashes and reboots with the information about
the causes.
analyze Now has an option -u to print page numbers of the
u. areas. A bug which prevented the distributed
analyze from working has been fixed.
bad144 Is a new program which prints out the DEC-
standard bad block information for a disk, or
puts it back if it gets clobbered. The name of
the program comes from the fact that the program
deals with ``DEC standard 144'' format.
badsect Creates a file in a file system which contains a
specified disk sector of that file system. This
is a primitive way of dealing with bad sectors,
but works on drivers which don't (yet) have bad
block forwarding according to the standard.
getty No longer prints ``Virtual'' in front of the sys-
tem identification, since there are no swap sys-
tems in sight anymore.
halt Now properly shuts down the system; see reboot
below for details.
July 14, 1981
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icheck Now properly sets the tfree field in the super-
block.
init Now interacts with halt, reboot and shutdown to
bring about orderly system shutdowns. No longer
writes entries in the /usr/adm/wtmp accounting
file when a getty process dies without a user
logging in on a terminal. Prints a warning mes-
sage (on the console) if a terminal exists, is
enabled, but the open returns an error, and waits
for terminal to be openable, checking each
minute, to prevent thrashing in this case.
last Now distinguishes between system shutdowns and
system crashes.
lastcomm A bug causing a core dump if user id's not
present in the password file were encountered has
been fixed.
login Now interacts with the shutdown command to forbid
logins (except by the super-user) in the last 5
minutes before a shutdown (detected by the pres-
ence of the file /etc/nologin, which also con-
tains a message about why the system is shutting
down which is presented to the rejected users.)
Implements a notion of ``secure terminals''; if
the file /etc/securetty exists, then it should
contain a list of the secure terminals where root
is allowed to login. If this file does not
exist, then root can log in anywhere, as before.
If a user tries to login but can't get to their
home directory they are left in the root direc-
tory and warned, so that they have some chance to
send mail about or fix the problem themselves.
If a file .hushlogin exists in a users home
directory the the message of the day and other
such information designed for human users will
not be printed at login time. This is specifi-
cally designed for the user uucp which is another
computer and just ignores such stuff anyways.
Finally a bug has been fixed which cause login to
core dump if there were tabs in the file
/etc/ttytype.
mkfs Now works properly when given a proto argument;
previously it complained because it didn't know
that the format of the file /usr/mdec/uboot had
been changed.
pstat Has new flags -m and -g which interpret the mul-
tiplexor data structures.
July 14, 1981
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reboot Now shuts the system down cleanly, stopping all
system activity before initiating the reboot pro-
cedure. Normally, however, the new shutdown com-
mand is used to take the system down, notifying
the users of the impending downtime. The options
-s and -a options to reboot are no longer avail-
able, as it will not be possible to provide them
on all VAX cpu's due to the way the console
interface works. Instead, you can halt the pro-
cessor using halt which puts the system into a
tight loop, and then perform the desired reboot
sequence manually at the console. This works on
both 11/750 and 11/780 processors.
renice Has been modified for the new kernel and is no
longer dependent on system configuration parame-
ters; it no longer needs to be recompiled when
system table sizes change.
restor Now properly handles the case where dump files
are contained in dump tapes; previously the end
of the embedded dump would confuse restor and
cause the rest of the dump tape to be inaccessi-
ble.
sa Now correctly handles an arbitrary number of com-
mands and users. Two new options have been added
-v and -f giving it a googol+2 options. See
sa(8) for details.
savecore Is a new program which runs after a reboot to
save check to see if the system had crashed and,
if it had, to save any core image which was suc-
cessfully written to the paging area. See
savecore(8) for a full description.
shutdown Is a new command which shuts the system down at a
specified time. It broadcasts messages to users
warning them as the downtime approaches, records
the reason for the reboot in a log file, and
cooperates with init in a cleanly shutdown (e.g.
during the last 2 minutes of system operation,
users attempting to log in are told that the sys-
tem is going down and the reason for the shutdown
but not allowed to log in.)
July 14, 1981
