Crash Dump Problem

[rajasekar.m]

Hi,

i have created the new LV for for dump and removed the default dump.

but i am unble to see the crashconf -v o/p.

# crashconf -v
Crash dump configuration has been changed since boot.

CLASS PAGES INCLUDED IN DUMP DESCRIPTION
-------- ---------- ---------------- -------------------------------------
UNUSED 717485 yes, forced unused pages
USERPG 120028 yes, forced user process pages
BCACHE 13421 yes, forced buffer cache pages
KCODE 9916 yes, forced kernel code pages
USTACK 936 yes, forced user process stacks
FSDATA 28 yes, forced file system metadata
KDDATA 172088 yes, forced kernel dynamic data
KSDATA 6445 yes, forced kernel static data
SUPERPG 5108 yes, forced unused kernel super pages

Total pages on system: 1045455
Total pages included in dump: 1045455

Dump compressed: ON

Dump Parallel: ON

DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
------------ ------------ ------------ ------------ -------------------------
3:0x000000 2578272 8388608 64:0x000002 /dev/vg00/lvol2
3:0x000000 43013984 4194304 64:0x00000a /dev/vg00/lvdump
------------
12582912
Persistent dump device list:
/dev/vg00/lvol2
# lvlnboot -v
Boot Definitions for Volume Group /dev/vg00:
Physical Volumes belonging in Root Volume Group:
/dev/disk/disk36_p2 -- Boot Disk
Boot: lvol1 on: /dev/disk/disk36_p2
Root: lvol3 on: /dev/disk/disk36_p2
Swap: lvol2 on: /dev/disk/disk36_p2
No Dump Logical Volume configured

Please let me know the step by step to configure the crash dump.

[Vivek Bhatia]

Hi,

Please have a look.

crashconf (both the system call and the command) can also be used to configure the classes of memory that will be included in, or excluded from, the dump. If desired, this information can also be configured at kernel build time, by setting the bitmask tunables alwaysdump and dontdump. Refer to the /usr/include/sys/crashconf.h file or the output of the crashconf(1M) command for the current list of memory classes.

In most circumstances, it should not be necessary to modify the list of individual memory classes to be dumped. The default settings provide adequate information for debugging nearly all system panics while eliminating as much extraneous data from the dump as possible.

In actual practice, if crash dump is reconfigured at all, it is usually done to force a full dump, or to disable dumps entirely.

Full dumps are enabled by including all pages in the dump. This is done with "crashconf -i all" or by setting CRASH_INCLUDED_PAGES="all" in /etc/rc.config.d/crashconf.Dumps are disabled by excluding all pages from the dump. Again, this is done with "crashconf -e all" or by setting CRASH_EXCLUDED_PAGES="all" in /etc/rc.config.d/crashconf.

Finally, crashconf(1M) uses the pstat interfaces pstat_getcrashinfo(2) and pstat_getcrashdev(2) to provide a report of which devices are configured, which memory classes will be included, and how much space a selective dump will take. This information can be used to determine the amount of dump space that should normally be configured. Specifying "-v" on the crashconf(1M) command line will display the current crash dump configuration to verify that the expected changes have taken effect.


How Much Dump Space Do I Need?

For selective dumps, use crashconf(1M) to find out how much space would be needed for a selective dump of your machine. (Use the -v flag, and run it while your system is under its normal or higher than normal workload.) The space needed will vary depending on the workload of the machine, so add another 25% or so to be safe. The total dump space should meet or exceed this amount.

For machines that are relatively stable and don't expect to dump often, this is enough. If a full dump is needed from such a machine, additional space can be configured for it on the fly, anyway. This space can also be used for swap unless reboot times are critical.

For machines on which full dumps are required, the full size of physical memory, plus a little bit for dump headers and tables, should be configured as dump space. At least the amount needed for a selective dump should be configured on a device that is not used for swap activity.

For example, the size of a selective dump for a 1GB RAM system typically ranges from 100MB to 200MB (10% to 20%). Extrapolating this to a 64GB system, a dump could be as large as 12GB.

Whenever you have dump devices that are not also used for swap activity, make sure that they are configured last. This will cause them to be used first (dump goes from the end backward), which will minimize the chance of writing into an area shared by swap. Writing into swap space is undesirable because it will slow down your reboot processing; see â Post-Reboot Dump Processingâ , for details.

[rajasekar.m]

ya i read the docs,but i need to know the command to remove the entries in crashconf..

DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
------------ ------------ ------------ ------------ -------------------------
3:0x000000 2578272 8388608 64:0x000002 /dev/vg00/lvol2
3:0x000000 43013984 4194304 64:0x00000a /dev/vg00/lvdump

please provide the step by step command to confiure the crashdump with new LV

[Vivek Bhatia]

Hi Raj,

Can you tell me that how have you added the dump device in crashconf.

Regards
Vivek Bhatia

[Ninad_1]

Hi,

Assuming that the new dump volume you have created is lvdump2 (also assuming that you have created the dump device as contigous one with no bad block relocation while creating the lvol)
Then to add it you need to use the command
lvlnboot -d /dev/vg00/lvdump2

If crashconf shows old entried, then you need to use the -r option with crashconf to replace the existing dump device entries with the new entry.

Thus the command should be
crashconf -rv /dev/vg00/lvdump2

This should replace all the dump device entries with this new one.

Regards,
Ninad