setting maxuprc on-the-fly

[Corey Lindsly]

it is my intent to raise the maxuprc (maximum user
processes) value from 30 to 100 on a SPARCstation 10/51
running Solaris 2.5, without rebooting the machine.
i discovered this procedure in an old c.s.s.a post:

Command to modify the runiing kernel :
adb -w -k /dev/ksyms /dev/mem <CR>
(exit with Ctrl-D)
it prints the variable physmem.
then u can type commands to alter varaiables values or print values.
maxusers/D : print maxusers value in decimal
maxusers/X : the same in hexa
maxusers/W0x200 : set maxusers to 200hex (beware : big W (uper) not w)

all variables may be modifiesd, by this way.

indeed, when i do this with maxuprc, it appears to
work. if i now query for the value in the running
kernel using adb, it shows the value at 100:

milhouse# adb -k /dev/ksyms /dev/mem
physmem 7df0
maxuprc/D
maxuprc:
maxuprc: 100

but i am still encountering fork() errors when a user tries
to spawn processes beyond the previous value of 30. is this
something that can only be set by changing the value in
/etc/system and rebooting? i would like to avoid that if
possible.

comments, suggestions welcome.

---corey

[Tony Walton]

Corey Lindsly wrote:
>
> is this [maxuprc]

> something that can only be set by changing the value in
> /etc/system and rebooting?

Yes. Tunables such as maxuprc are loaded very early in the boot
sequence into an internal kernel structure which is what the kernel
really uses. Messing with this internal kernel structure on a running
machine can be a very good way to bring about a system panic.

The only tunable I've found that can be safely played about with on a
running system is rstchown (though there may well be others).

Regards

Tony Walton
Sun Microsystems UK

This posting is not official support from Sun Microsystems. It's my own
opinion.

[Casper H.S. Dik - Network Security Engineer]

[[ PLEASE DON'T SEND ME EMAIL COPIES OF POSTINGS ]]

co...@phix.com (Corey Lindsly) writes:

>but i am still encountering fork() errors when a user tries
>to spawn processes beyond the previous value of 30. is this

>something that can only be set by changing the value in

>/etc/system and rebooting? i would like to avoid that if
>possible.

maxuprc is copied to the "v" variable in the kernel. Try this:

# adb -wk
v+0x1c/W<num>

Casper
--
Expressed in this posting are my opinions. They are in no way related
to opinions held by my employer, Sun Microsystems.
Statements on Sun products included here are not gospel and may
be fiction rather than truth.