.TH idtune "" "" "Command"
.PC "Set a tunable system value"
\fB/etc/conf/bin/idtune [\-fm] \fIswitch value\fR
.PP
The command
.B idtune
lets you ``tune'' a variable in the \*(CO kernel.
It also performs some sanity checking, to help ensure that you do not set
a value to an impossible value.
It and the related command
.B cohtune
largely replace the need for the command
.BR patch .
.PP
To use
.BR idtune ,
simply invoke it along with the variable you wish to modify and the value
to which you wish to set it.
For example, to change the maximum size of a shared-memory segment to
128,000 bytes, type the command:
.DM
	/etc/conf/bin/idtune SHMMAX 128000
.DE
.PP
.II idmkcoh
For the new setting to come into effect, you must use the command
.B /etc/conf/bin/idmkcoh
to build a new kernel, and then boot the newly built kernel.
.PP
.B idenable
recognizes the following two command-line options:
.IP \fB\-f\fR
.B idtune
by default will ask you if you are sure that you want to make a given change.
This option suppresses that behavior.
.IP \fB\-m\fR
Check that the value of
.I switch
is no less than
.IR value .
If the value
.I switch
is less than
.IR value ,
then
.B idtune
raises it to
.IR value ;
otherwise, it leaves the value of
.I switch
alone.
.PP
.II stune
.II /etc/conf/stune
.B idtune
works by modifying the file
.BR /etc/conf/stune ,
which holds the values of system variables that users can set.
.B stune
consists of a series of entries like the following:
.DM
.ta 0.5i 2.0i
	LOOP_COUNT	16
	DUMP_USERS	2
	MONO_COUNT	0
	VGA_COUNT	4
.DE
.PP
.II mtune
.II /etc/conf/mtune
The allowed range of values for a given variable is set in file
.BR /etc/conf/mtune ,
which consists of a series like the following:
.DM
	STREAMS_HEAP    8192    32768   131072
	MONO_COUNT      0       4       8
	VGA_COUNT       0       4       8
	NBUF_SPEC       0       0       5000
	NHASH_SPEC      0       1021    5000
	NINODE_SPEC     0       128     1024
	NCLIST_SPEC     0       64      1024
.DE
.PP
The first column gives the variable, the second gives its minimum allowable
value, the third gives its default value, and the last its maximum value.
.PP
You can read
.B mtune
and
.B stune
to see what kernel variables you can set,
and to find the range of values allowed for each.
Note, however, that you must
.I never
modify
.B stune
or
.B mtune
by hand.
If you do so, you may build a kernel that is unbootable
or that trashes your file system.
.SH "See Also"
.Xr "cohtune," cohtune
.Xr "commands," commands
.Xr "idenable," idenable
.Xr "idmkcoh" idmkcoh
