Does maxuprc apply to root?

Question

We need to limit the number of processes that can be executed by normal users on our Solaris 10 system. We have a lot of students who are just learning how fork() works, and the system has gone down twice now because it ran out of processes. Historically, there has always been a limit, but now, apparently, there isn't, and I need to institute one.
I've figured out that the way to do this is to set the maxuprc in /etc/system. If I do this, does it also limit the number of processes that root can run, or does it only apply to regular users?
Thanks!
Mike VanHorn
[email protected]

Answer 1

From Brandon Hutchinson at http://www.brandonhutchinson.com/Solaris_kernel_tunables.html
short answer - maxuprc is max user processes per user id, does not affect root.
e.g., determining current maxuprc kernel parameter with adb:
# adb -k
physmem f74c
maxuprc/D (display maxuprc value in decimal)
maxuprc:
maxuprc: 250
maxuprc/X (display maxuprc value in hexadecimal)
maxuprc:
maxuprc: fa
$q (exit out of adb)
Running sysdef also shows the values of certain kernel tunables.
e.g., dynamically adjusting maxuprc with adb:
maxuprc is a kernel tunable that defines the maximum number of concurrent processes per user ID. This value does not affect the root user.
The default maxuprc value is max_nprocs - reserved_procs.
# adb -kw
physmem f74c
maxuprc/D (display maxuprc value in decimal)
maxuprc:
maxuprc: 16389
v+0x1c/W0x12c (set maxuprc to 300; 0x12c is hexademical for 300)
$q (exit out of adb)
The change will be reflected in sysdef output, but not in adb. However, the change does take effect.
# sysdef | grep v_maxup
300 maximum processes per user id (v.v_maxup)
# echo maxuprc/D | adb -k
physmem 7dd2c
maxuprc:
maxuprc: 16389
When you exceed maxuprc, you will see the following:
bash: fork: Resource temporarily unavailable
sh: fork failed - too many processes
/var/adm/messages:
unix: out of per-user processes for uid \d+
To preserve this change after a reboot, add set maxuprc = 300 in /etc/system.