HP-UX HB v13.00 Ch-08 - Crash Dumps

HP-UX Handbook – Rev 13.00 Page 13 (of 38)
Chapter 08 Crash Dumps
October 29, 2013
NOTE: 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 section above).
NOTE: There are often questions like: “Why is the dump LV not mirrored like root, boot and
swap LVs are?”
# lvlnboot -v
Boot Definitions for Volume Group /dev/vg00:
Physical Volumes belonging in Root Volume Group:
/dev/dsk/c0t6d0 (10/0.6.0) -- Boot Disk
/dev/dsk/c0t5d0 (10/0.5.0) -- Boot Disk
Root: lvol1 on: /dev/dsk/c0t6d0
/dev/dsk/c0t5d0
Swap: lvol2 on: /dev/dsk/c0t6d0
/dev/dsk/c0t5d0
Dump: lvol2 on: /dev/dsk/c0t6d0, 0
Dump: lvdump on: /dev/dsk/c0t6d0, 1
The answer: the system dumps onto a previously configured area of the disk. The dump process
is a low level routine that bypasses the LVM layer, hence the data is not going to be mirrored.
The OS simply stored the hardware path of the disk and the starting and ending offset on this
disk at the time you activated it. This information is given by the dump LV. This is the reason
why dump LVs must be contiguous.
The dump/savecrash process
Writing the memory image to the dump devices
The kernel routine responsible for dumping is dumpsys().
Dump formats
There are four known dump formats. Which format you deal with can be found in the INDEX
file (grep version INDEX):
COREFILE (Version 0)
This format, used up through HP-UX 10.01, consists of a single file containing the physical
memory image, with a 1-to-1 correspondence between file offset and memory address.
Normally there is an associated file containing the kernel image. Sources or destinations of
this type must be specified as two pathnames to plain files, separated by whitespace; the first
is the core image file and the second is the kernel image file.