Compressed Dump

Compressed Dump White Paper, Version 1.3
page 16
-D dumpdevice dumpdevice is the name of the device containing the header of
the raw crash image. The console messages from the time of the
panic will identify the major and minor numbers of this device.
This option, in combination with -O, can be used to tell savecrash
where to find the dump in the rare instances that savecrash
doesn’t know where to look.
-Ooffset offset is the offset in kBytes, relative to the beginning of the
device specified with -D above, of the header of the raw crash
image. The console messages from the time of the panic will
identify this offset. This option, in combination with -D, can be
used to tell savecrash where to find the dump in the rare
instances that savecrash doesn’t know where to look.
-d sysfile sysfile is the name of a file containing the image of the system
that produced the core dump (that is, the system running when
the crash occurred). If this option is not specified, savecrash gets
the file name from the dump itself. If the file containing the image
of the system that caused the crash has changed, use this option
to specify the new file name.
-m minfree is the amount of free space (in kBytes) that must be available for
ordinary user files in the file system into which the dump will be
saved, in addition to space reserved for the superuser. If neces-
sary, only part of the dump will be saved to achieve this require-
ment. savecrash calculates the amount of disk space available
when it starts saving the dump. Any space used by other pro-
cesses while dump is being saved is not taken into account. min-
free may be specified in bytes (b), kilobytes (k), megabytes (m),
or gigabytes (g). The default minfree value is zero, and the
default unit is kilobytes.
-s chunksize chunksize is the size (default kBytes) of a single physical memory
image file before compression. The kByte value must be a multi-
ple of page size (divisible by 4) and between 64 and 1048576.
chunksize may be specified in units of bytes (b),kilobytes (k),
megabytes (m), or gigabytes (g). Larger numbers increase com-
pression efficiency at the expense of both savecrash time and
debugging time. If -s is not specified, a default is chosen based
on the physical memory size and the amount of available file sys-
tem space. If the dump image on the dump device is com-
pressed, then the chunksize specification is only used as a size
limit for the images copied into the file system. See crashconf(2).
If the size specified is smaller than the chunk size used for com-
pression while dumping, then a warning message will be printed
and the compression chunk size used by the dump will be used to
create the file system images.
-t tapedevice tapedevice is the tape device where the crash dump will be writ-
ten. Crash dumps that are written to tape are written using a tar
format. The crash dump tape can be read using tar(1).
When the -t option is specified, the -p option is not allowed and
the whole dump is always preserved. In addition, -c and -l, are
not allowed and -m is ignored. Also, when -t is specified, save-