about dynamic kernel parameter

hongjing_zhang — Thu, 26 Sep 2002 00:31:40 GMT

There are some dynamic kernel parameters on 11i.I know the machine have not to reboot if I change dynamic parameter,but when the machine reboot,why dynamic parameter is changed to the value before?
(l2000,11i)

Re: about dynamic kernel parameter

Telia BackOffice — Thu, 26 Sep 2002 00:50:05 GMT

Are you using sam?
if not then use sam!

BR,
Jannik

Re: about dynamic kernel parameter

Animesh Chakraborty — Thu, 26 Sep 2002 00:52:20 GMT

Dynamic tunables are not preserved after a reboot. DocId: UKRNKBRC00010259 Updated: 8/2/02 4:57:00 AM

PROBLEM
Using kmtune or Sam to set dynamic kernel parameters is losing the
value after a reboot.

For example:

# kmtune -s shmmax=0x40000000

# kmtune -u
The kernel's value of shmmax has been set to 1073741824 (0x40000000).

# kmtune -l -q shmmax
Parameter: shmmax
Current: 0x40000000
Planned: 0x40000000
Default: 0X4000000
Minimum: -
Module: -
Version: -
Dynamic: Yes

Everything appears to work, but when the system is rebooted with
shutdown -r, the values revert back to a previous setting.

What is going on?
RESOLUTION
In this case, the krsd daemon was not running so the configuration
files in /stand/krs/ were not getting updated. The krsd daemon should be
started in /etc/inittab as follows:

krsd:123456:respawn:/sbin/krsd -i

If this is not there, it should be added. Then do init q.

Once the daemon is restarted, the files in /stand/krs should be rebuilt. This
can be done with the kmtune command. In this example shmmax is being modified,
but using kmtune -s on any dynamic parameter would work:

# mv /stand/krs/* /tmp
# kmtune -s shmmax=0x40000000
# kmtune -u

Using cksum on the new files in /stand/krs will probably show
different sizes than the original ones. This is because the new values have
now been set correctly.

# cksum /stand/krs/*
4067031556 65048 /stand/krs/_stand_vmunix.krs
3908630881 24 /stand/krs/system.krs

The kernel parameter value should now survive a reboot.

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