idtune -- Command

Set a tunable system value
/etc/conf/bin/idtune [-fm] switch value

The command idtune lets you ``tune'' a variable in the COHERENT 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 cohtune largely
replace the need for the command patch.

To use 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:

    /etc/conf/bin/idtune SHMMAX 128000

For  the  new  setting to  come  into  effect,  you  must use  the  command
/etc/conf/bin/idmkcoh to build a new  kernel, and then boot the newly built
kernel.

idenable recognizes the following two command-line options:

-f   idtune by default will ask you if you are sure that you want to make a
     given change.  This option suppresses that behavior.

-m   Check that  the value of  switch is no  less than value.  If the value
     switch is less than value,  then idtune raises it to value; otherwise,
     it leaves the value of switch alone.

idtune works by modifying  the file /etc/conf/stune, which holds the values
of system  variables that  users can  set.  stune consists  of a  series of
entries like the following:

     LOOP_COUNT     16
     DUMP_USERS     2
     MONO_COUNT     0
     VGA_COUNT      4

The  allowed  range  of  values  for  a  given  variable  is  set  in  file
/etc/conf/mtune, which consists of a series like the following:

    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

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.

You can read mtune and stune  to see what kernel variables you can set, and
to find the range of values allowed for each.  Note, however, that you must
never modify stune or mtune by  hand.  If you do so, you may build a kernel
that is unbootable or that trashes your file system.

See Also

cohtune,
commands,
idenable,
idmkcoh

© 2012 by Stephen A. Ness