Using the crash(ADM) diagnostic tool

Defining the default dump device

If your system crashes, it writes its memory image to the dump device. The default dump device is the swap area, /dev/swap, but you can define an alternative dump device in one of two ways:

by using the dump bootstring at the Boot: prompt, or by including this as part of the default bootstring in the boot defaults file, /etc/default/boot; see the bootstring(HW) and boot(F) manual pages for more information. You can specify a tape drive as the dump device. For example:

dump=Stp(8)

dump=ct(8)
define the dump device to be a SCSI tape drive or a cartridge tape drive respectively. This can be useful if the size of the swap area is too small to hold the system image -- if, for example, you have configured a swap area smaller than the amount of physical memory on your system.
If you do not want the system to save its memory image, specify:

dump=none
by redefining the system default dump device in the file /etc/conf/cf.d/sassign; this definition will be included in the kernel when you next rebuild it. Using sassign(F) in this way, you can also define a tape drive as the dump device. For example:

dump Stp 8

dump ct 8
define the dump device to be a SCSI tape drive or a cartridge tape drive, respectively.
Note that you must edit sassign(F) and then relink the kernel to redefine the dump device.

If your system dumps its image to the swap area, it runs the dumpsave(ADM) command when it is next booted. This allows you to save the memory image to tape or floppy disk for later analysis.

NOTE: If you intend to analyze a memory image on a different system than the one that crashed, you must make a copy of the kernel program file that was running on the system that crashed. You cannot examine a memory image without this file -- crash needs it to access its symbol table.

If you also need to find out which files were open to processes at the time of the crash, you will also need to copy the contents of the filesystems.

The complementary command ldsysdump(ADM) copies a memory image from tape or floppy disk to a file:

/etc/ldsysdump filename

To check the validity of a memory image, you can use the memsize(ADM) command:

/etc/memsize filename

memsize returns an error if the memory image is corrupted.