Managing Systems and Workgroups: A Guide for HP-UX System Administrators
Administering a System: Booting and Shutdown
Abnormal System Shutdowns
Chapter 5 541
If it is critical to you to capture every byte of memory in all instances, including
the early stages of the boot process, define enough dump space in the kernel
configuration to account for this.
NOTE The preceding example is presented for completeness. The actual amount of time
between the point where kernel dump devices are activated, and the point where
runtime dump devices are activated is very small (a few seconds), so the window
of vulnerability for this situation is practically nonexistent.
Using a Device for Both Paging and as a Dump Device It is possible to use
a specific device for both paging purposes and as a dump device. But, if crash
dump integrity is critical to you, this is not recommended. From the savecrash
(1M) manpage:
If
savecrash
determines that a dump device is already enabled for paging,
and that paging activity has already taken place on that device, a warning
message will indicate that the dump may be invalid. If a dump device has
not already been enabled for paging,
savecrash
prevents paging from
being enabled to the device by creating the file
/etc/savecore.LCK
.
swapon
does not enable the device for paging if the device is locked in
/etc/savecore.LCK
...
So, if possible, avoid using a given device for both paging and dumping:
particularly the primary paging device!
Systems configured with small amounts of memory and using only the primary
swap device as a dump device are in danger of not being able to preserve the
dump (copy it to the HP-UX file system area) before paging activity destroys the
data in the dump area. Larger memory systems are less likely to need paging
(swap) space during startup, and are therefore less likely to destroy a memory
dump on the primary paging device before it can be copied.
Disk Space Needs Use this section if the you have very limited disk
resources on your system for the post-crash dump and/or the post-reboot
save of the memory image to the HP-UX file system area. The factors you
have to consider here are:
• “Dump Level” on page 542
• “Compressed Save versus Noncompressed Save” on page 542
• “Partial Save (savecrash -p)” on page 542