How do I recover from a nonreboot after a kernal change?

[Dana Blanton]

HP9000 model H50 with UNIX 11.0.

I made some changes to the kernal via SAM for an application upgrade. Process new kernal initiated a reboot. Now server errors and hangs when rebooting with an error "Panic instruction page fault" "stktrc can't find descriptor"
0x00224e00 0x0034920c 0x000e48e4 0x00234274 0x00000000
I'd like to get to single user mode and copy back the original kernal (/stand/vmunix????) but I don't know how.
Thanks

[Robert-Jan Goossens · Accepted solution]

Hi,

In your case start with 6.1

PROBLEM
The kernel have just been rebuilt, the machine shutdown and restarted, but it
doesn't reboot anymore. The kernel is corrupted! What are the steps to
recover from this situation?




RESOLUTION

Recovery will require booting from the previous kernel or any other kernel that
was backed up previously.

1 - Login as root. Make sure there is enough disk space to save the
current kernel files, if desired.

2 - After turning on the system, when the message "Press escape to stop boot
sequence" is displayed, press the "escape" key to get into the PDC (Product
Dependant Code). A list of available commands will be displayed with
the "BOOT_ADMIN>" prompt.

3 - Type "bo pri isl" and [return] to get to the "isl" command
prompt "ISL>".

4 - Boot from desired kernel.

To boot normally from the previous kernel, type:
"hpux (;0)/stand/vmunix.prev" and [return].

To boot in "single user" mode from the previous kernel, type:
"hpux -is (;0)/stand/vmunix.prev" and [return].

To boot in "lvm maintenance" mode from the previous kernel,
type "hpux -lm (;0)/stand/vmunix.prev" and [return].

Note : To boot from an other previously backed up kernel, replace the kernel
file name "vmunix.prev" with the file name of the kernel to boot.

Note that the kernel files are :
/stand/vmunix - A file containing the kernel itself.
/stand/system - A file containing the kernel configuration.
/stand/dklm/* - A directory containing a few files and directories for
kernel configuration purposes (for HP-UX 11.0 and up only).

5.1 - Backup the current kernel files (for investigation.. ,ex: .bak):
mv /stand/vmunix /stand/vmunix.bak
mv /stand/system /stand/system.bak
mv /stand/dlkm /stand/dlkm.bak (for HP-UX 11.0 and up only)

OR

5.2 - Delete the current kernel files (to save space):
rm /stand/vmunix /stand/vmunix
rm /stand/system /stand/system
rm -r /stand/dlkm/* (for HP-UX 11.0 and up only)

NEXT

6.1 - Install the previous good kernel to be booted (.prev) to the current
kernel file name :
cp /stand/vmunix.prev /stand/vmunix
cp /stand/system.prev /stand/system
cp -R -p /stand/dlkm.vmunix.prev/* /stand/dlkm (for HP-UX 11.0 and up only)

OR

6.2 - Or Install the desired kernel you want to boot (ex: .ori) to the current
kernel file name :
cp /stand/vmunix.ori /stand/vmunix
cp /stand/system.ori /stand/system
cp -R -p /stand/dlkm.ori/* /stand/dlkm (for HP-UX 11.0 and up only)


------
Note : For information on doing your own kernel backup, refer to KBRC00008093
Backing up current kernel files for safety.

Robert-Jan.

[Rita C Workman]

* * Tip * *

You have just gotten the info on how to boot up off your previous vmunix (last good kernel).

Now for the tip...

Once you get back up... Remember to go out to /stand and copy that vmunix.prev to something like vmunix.good !!

Why??...because when you attempt to build the new kernel again (recommend doing it completely with the manual build procedures)..it will again move the current (albeit bad one) into the vmunix.prev position. Thus leaving you with not one good vmunix to boot from. By copying the current (albeit old but good) vmunix.prev to vmunix.good you have covered yourself in case your next reboot goes sour. So you could then reboot on /stand/vmunix.good

* * Like I said...just a tip * * NPN...

Rgrds,
Rita

[Dana Blanton]

Thanks for the tips. I was able to recover by booting and going into ISL mode and booting from the /stand/vmunix.prev file.

[Steven E. Protter]

After you boot, copy your vmunix.prev file to overwrite vmunix

Then its time to figure out what caused the problem. You need to verify the integrity of your system files as well.

Did you by chance accidently try a second install on the LITS patch PHKL_18543

Bad karma there, but it can be painfully recovered from.

P

[Martin Johnson]

Another tip.

make sure /stand is big enough to handle multiple copies of the kernel. If not, do an ignite backup/recovery. Interrupt the recovery to increase the size of /stand. (You may also want to increase / also.)

HTH
Marty