systune - display and set tunable parameters
systune [ -bfir ] [ -n name ] [ -p rootpath ]
[ variable [ value ] ]
systune is a tool that enables you to examine and configure your tunable
kernel parameters. systune can adjust some parameters in real time and
informs you if you need to reboot your system after reconfiguration. It
saves the reconfigured kernel in /unix.install, unless the -f option is
systune has two modes: interactive and noninteractive. Interactive mode
allows you to query information about various portions of tunable
parameters or to set new values for tunable parameters. Some parameters
can be changed while the system is running, and some require a new copy
of the kernel to be booted. To enter interactive mode, use the -i
option. In noninteractive mode, systune displays the values of one
tunable parameter or group of tunable parameters, or allows the value of
one tunable parameter to be changed. Note that you will still be
prompted for a confirmation when changing a parameter in noninteractive
mode. To avoid interacting with the confirmation you must use additional
commands, for example:
# echo y | systune nproc 400
Noninteractive mode is the default.
The options are:
-b Both target kernel and the running system are updated with the
new values that you specified, if the new values are within the
legal range for the parameter specified in /var/sysgen/mtune.
The new values with the corresponding tunable variables are also
added into /var/sysgen/stune file. This is the default behavior.
-f This option forces systune to not save the reconfigured kernel in
/unix.install. By default, systune tests to see if /unix.install
exists and whether it is identical to the running system. If it
is identical, systune makes any changes in /unix.install;
otherwise, systune copies the current /unix kernel or the kernel
specified by the -n option to /unix.install and makes all changes
to the copied kernel. If the copy fails for any reason, such as
lack of disk space or the presence of the -f option, the
currently running kernel is changed.
-i Run systune in interactive mode. When systune is invoked in
interactive mode, no parameter values are immediately displayed.
Instead, you see the systune prompt:
The commands available in interactive mode are described below.
-n name This option specifies an alternate kernel name to tune in place
If you specify this option, rootpath becomes the starting
pathname for systune to check for /var/sysgen/stune and
/var/sysgen/mtune. The default rootpath directory is /.
-r The new values change on the running system only. If the tunable
parameter can not be changed on the running system, nothing is
affected. The default is -b.
If the name of a variable is specified on the command line, its current
value is displayed. If the name of a group is specified on the command
line, the names and values of all variables in that group are displayed.
If the name of a variable and a value are specified on the command line,
the variable's value is changed after verification and confirmation.
The systune commands available in interactive mode are:
quit Quit systune immediately. Any changes you have made up to that
point are saved and cannot be discarded. You must go through and
change back any parameters that you do not wish to be changed.
all Print information on all tunable parameters. This command
displays the same information as systune invoked in
help Show all the built-in commands and group names. systune lists
two commands (help and all) and the groups of kernel tunable
parameters. Each group of tunable parameters is organized so
that related parameters are kept together. For example, the
numproc parameter group contains parameters related to the number
of processes allowed to run on the system at any given time. Its
ncsize = 808 (0x328)
ncallout = 40 (0x28)
callout_himark = 332 (0x14c)
ndquot = 808 (0x328)
nproc = 300 (0x12c)
Display information for all the tunable parameters in this group
along with their values in decimal numerals and in hexadecimal
Display information for this tunable parameter only.
Set the specified tunable parameter to the new value. For
example, to raise the nproc parameter in the numproc parameter
group from 300 to 400, follow this example:
systune-> nproc 400
nproc = 300 (0x12c)
Do you really want to change nproc to 400 (0x190)? (y/n) y
In order for the change in parameter nproc to become
effective, /unix.install must be moved to /unix and the
This message tells you that the change does not take effect until
a new kernel with the new value is running on your system.
systune always prints a message to inform you if you need to
reboot your system for a kernel change to take effect.
systune makes all requested changes to the kernel in three
places, if possible. (Nondynamically adjustable parameters can
be changed in only two out of three places.) The parameters are
o the running kernel image on the workstation
o the /unix or /unix.install file
o the /var/sysgen/stune file
Some sanity checking is performed on the modified kernel
parameters to help prevent the creation of kernels that will not
function correctly. This checking is performed both by systune
and by the lboot(1M) command. For example, some variables have
preset minimum and maximum values. Any attempt to change the
variable beyond these threshold values results in an error
message, and the variable is not changed.
When the system calculates its default value for a systune, the resulting
value may be outside the valid range provided by the mtune file. For
example, if you set mbmaxpages to 0 (i.e. ask system for default value)
then on a 32-bit system with 256M of RAM the default is set to 16384.
However the maximum allowed by mtune is 8192. In this example, the
system will configure mbmaxpages to 16384 from the default of 0, but it
is not possible to assign mbmaxpages > 8192 directly from systune because
of the restriction in mtune.
/var/sysgen/mtune/* system tunable parameters
/var/sysgen/stune local settings for system tunable parameters
autoconfig(1M), lboot(1M), mtune(4), stune(4).
PPPPaaaaggggeeee 4444 [ Back ]