SET4(8) — MAINTENANCE COMMANDS
NAME
set4, unset4, check4 − set, unset, and check the 4 megabyte process virtual address space limit flag in a Sun386i module
SYNOPSIS
set4 [ −d working_directory ] [ − | filename ] ...
unset4 filename...
check4 filename...
AVAILABILITY
Available only on Sun 386i systems running a SunOS 4.0.x release or earlier. Not a SunOS 4.1 release feature.
DESCRIPTION
set4 sets the 4 megabyte process memory flag in each filename program image, limiting the virtual address space for each program to 4 megabytes. If a ‘−’ is used, set4 reads the standard input for a list of files to set the 4 megabyte limit on. Lines in the standard input whose first character is ‘#’ are ignored, so files may include comments.
unset4 clears the 4 megabyte process memory flag in the program image, so the process virtual address space is not limited to 4 megabytes.
check4 reports programs that do not have the 4 megabyte limit set, and does not report programs with the limit set.
OPTIONS
−d working_directory
This specifies a directory prefix for file names that set4 processes.
EXAMPLES
Suppose that the file small_progs contains the following:
# These files should have their virtual address spaces limited to 4 MB:
/bin/date
/bin/true
Then the following command will run set4 on /build/bin/false, /build/bin/date, /build/bin/true, and /build/bin/cat.
example% set4 −d /build /bin/false −
/bin/cat < small_progs
example%
In this example, unset4 clears the 4 megabyte limit flag in date, and clri.
example% unset4 /bin/date /etc/clri
example%
In the last example, check4 shows that date and clri are 4 megabyte processes, but basename is not.
example% check4 /bin/date /etc/clri /usr/bin/basename
basename is not a 4MB process
example%
SEE ALSO
BUGS
There is a problem in the way that processes that have the 4 megabyte limit set exec() processes that do not have the limit set. (See execve(2V) and execl(3V) for descriptions of exec() processing.) For a short time during the exec(), a child has the parent’s data and stack limits. During this time, the program is checked to see if it will fit into memory. If the parent had the 4 megabyte limit set, the test fails, because the child program is running with the parent’s 4 megabyte limit. This only affects programs which have more than 4 megabytes of global or static data compiled into the program. It does not affect programs which use malloc(3V) to obtain memory.
For example, csh(1) and sh(1) may be 4 megabyte processes. If they are, and if you try to run a program with more than 4 megabytes of global and static data, the shell cannot successfully exec(). To fix this problem, become root on your machine and enter the following commands:
example% /etc/mount −o remount,rw /usr
/usr/etc/unset4 /bin/csh /bin/sh
example%
Then log out and back in again to run the modified shell. This makes csh and sh “normal” processes.
Sun Release 4.1 — Last change: 6 October 1989