Kernel parameters

[Arockia Jegan]

I have HP box running HP-UX 11.11. I have changed the kernel parameters shmmax to 1GB and shmseg to 10. Those parameters are dynamic parameters. After installing patches (Dec 2001 latest patches) the parameters got changed to the default values.
Do u guys have any idea about this problem?

Thanks,
Arockia.

[Michael Tully]

Hi,

Really dumb question for you. Did you happen to run the 'kmupate' program after generating your kernel with the new parameters? If you didn't and rebooted you would have all of the old parameters. This would also occur if you loaded a patch bundle. You can only generate and use one kernel at a time. I have this bundle loaded on six boxes none having this problem.

-Michael

[Mark Greene_1]

How did you do both the initial kernel update and the patchload: sam or the command line?

mark

[Arockia Jegan]

Hi Mic.,

I have done through sam. I have changed 10 parameters (static & dynamic - including
shmmax & shmseg) and rebuild the kernel and rebooted the system. It was having the modified kernel parameter values. System got rebooted 4 to 5 times. I didn't have any problem. After installing the patches (GOLDPQK11i) system got rebooted and then only shmmax and shmseg got changed.

[Gamoji Raghavendra]

Hi Arockia,
How are viewing these kernel parameters? Is it through SAM or are you using kmtune command.
Both of them might show misleading information because your /stand/system might not be updated and so these tools get the information from /stand/system.

One way to determing if really the parameters are changed or not is to get their current values from the running kernel. Use the command below :
echo shmmax/D | adb -k /stand/vmunix /dev/mem

If you see the values you updated with, then its okay.

Hope this helps!

Bye,
Raghu.

[Vasudevan MV]

Hi,

Steps for building the new Kernel (tuning) manually :

1. Change directories to /stand/build.
cd /stand/build

2. Create a new system file from the running kernel.
/usr/lbin/sysadm/system_prep -s system

3. Edit the kernel with the planned changes.

kmtune -S /stand/build/system -s parm_name=value

4. Build the new kernel.
/usr/sbin/mk_kernel -s ./system

5. Move the old system and vmunix files so if anything goes wrong, the system
can be booted from the old kernel.
mv /stand/system /stand/system.prev
mv /stand/vmunix /stand/vmunix.prev
mv /stand/dlkm /stand/dlkm.vmunix.prev

6. Move the new system file and new kernel into place, ready to be used when
rebooting the system.
mv /stand/build/system /stand/system
kmupdate /stand/build/vmunix_test

7. Reboot the system off the new kernel.
shutdown -r

Hope this helps.

Vasu

[Don Morris_1]

Hmm... I know that the dyn tunes keep the current value in the Kernel Registry Service for the appropriate kernel -- and I don't think the system file gets updated (after all, why would it? The KRS will return the right value). It sounds like the patch process generates a new KRS based on the system, master.d, and space.h.d files instead of seeding from the current one so you go back to a 'default' state. Granted, I could be completely wrong -- but that's what it sounds like to me.

On the plus side, this should only affect dynamic tunables - so you can reset your values back quickly.

On the minus side -- you really shouldn't be expected to do that.

I'll check into this and see what I can find out.

Don

[Don Morris_1]

Hmm... well, nothing like being completely and utterly wrong in the above. Please disregard it.

Dynamic tunable changes _are_ propagated to the system file just as static tunable changes are, so the rebuild of the kernel after the patch process should have kept your values.

Did you perchance restore your system file from a backup before patching?

Don

[Bill Marmagas_1 · Accepted solution]

I know this thread is old, but note the recent information form HP below:

-----Original Message-----
From: HARPER,CHERYL (HP-USA,ex1) [mailto:cheryl_harper@hp.com]
Sent: Friday, June 21, 2002 9:22 AM
Subject: Proactive Notification: HPUX 11i Dynamic Kernel Parameters - Don 't survive patching activities!


Are you running HP-UX 11i? If so, read on...

HPUX 11i allows certain kernel parameters to be changed on the fly without rebooting.

When installing kernel intrusive patches with SD-UX, where a kernel rebuild is required, any previously set Dynamic Kernel Parameters (in almost all cases) will be set back to their original default values.

The issue is based on the get_sysfile command that is used to extract the current kernel settings is apparently unaware of the dynamic parameter settings. This issue has been reported to the lab and will be fixed in the near future.

Workaround

Prior to patching, issue a command to save the currently tuned parameters in a file for future use:
#kmtune | grep Y | egrep -v "-" | awk '{print $1, $2}' > /tmp/dyn_parms
After the patch installation, in order to stage the changes needed, issue the command :
#kmtune -u -S /tmp/dyn_parms
HPUX will read the file, and attempt to change to all kernel parameters. Those that it can't update (fixed parameters) it will issue WARNINGS on, and those dynamic parameters it can set, it will set to change pending. To verify the pending state, you could issue the following command:


#kmtune | grep Y | egrep -v "-"
To make the activate the changes, enter the command:
#kmtune -u
Since the parameters that you are setting are dynamic, no reboot will be required.

Hope this helps!