Compressed Dump

Compressed Dump White Paper, Version 1.3
page 14
savecrash(1M) savecrash(1M)
NAME
savecrash - save a crash dump of the operating system
SYNOPSIS
/sbin/savecrash [-cflprvzZ] [-D dumpdevice -O offset] [-d sysfile]
[-m minfree] [-s chunksize] [-t tapedevice]
[-w NOSWAP|SWAPEACH|SWAPEND] [dirname]
DESCRIPTION
savecrash saves the crash dump information of the system (assuming one was
made when the system crashed) and writes a reboot message in the shutdown log
file.
dirname is the name of the existing directory in which to store the crash dump; the
default is /var/adm/crash.
savecrash saves the crash image and related files in the directory dirname/crash.n.
The trailing n in the directory name is a number that increases by one every time
savecrash is run with the same dirname. This number is kept in the file dirname/
bounds, which is created if it does not already exist.
Usually, savecrash creates the INDEX file in the crash directory from the crash
dump header, copies all kernel modules that were loaded in memory at the time of
the crash, and copies all dump device contents into crash image files.
When savecrash writes out a crash dump directory, it checks the space available on
the file system containing dirname. savecrash will not use that portion of the file
system space which is reserved for the superuser. Additional space on the file sys-
tem can be reserved for other uses with -m minfree, where minfree is the amount of
additional space to reserve. This option is useful for ensuring enough file system
space for normal system activities after a panic.
If there is insufficient space in the file system for the portions of the crash dump that
need to be saved, savecrash will save as much as will fit in the available space. (Pri-
ority is given to the index file, then to the kernel module files, and then to the physi-
cal memoryimage.) The dump will be considered saved, and savecrash will not
attempt to save it again, unless there was insufficient space for any of the physical
memory image. (See the description of option -r.)
savecrash also writes a reboot message in the shutdown log file (/etc/shutdownlog),
if one exists. (If a shutdown log file does not exist, savecrash does not create one.)
If the system crashes as a result of a kernel panic, savecrash also records the panic
string in the shutdown log.
By default, when the primary paging device is not used as one of the dump devices
or after the crash image on the primary paging device has been saved, savecrash
runs in the background. This reduces system boot-up time by allowing the system
to be run with only the primary paging device.