savecrash(1M)savecrash(1M)NAMEsavecrash - save a crash dump of the operating system
SYNOPSIS
dumpdevice offset] sysfile] minfree] chunksize] tapedevice] [dirname]
DESCRIPTION
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
saves the crash image and related files in the directory The trailing n
in the directory name is a number that increases by one every time is
run with the same dirname. This number is kept in the file which is
created if it does not already exist.
Usually, creates the 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 writes out a crash dump directory, it checks the space available
on the file system containing dirname. will not use that portion of
the file system space which is reserved for the superuser. Additional
space on the file system can be reserved for other uses with minfree,
where minfree is the amount of additional space to reserve. This
option is useful for ensuring enough file system space for normal sys‐
tem 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, will save as much as will fit in
the available space. (Priority is given to the index file, then to the
kernel module files, and then to the physical memory image.) The dump
will be considered saved, and will not attempt to save it again, unless
there was insufficient space for any of the physical memory image.
(See the description of option
also writes a reboot message in the shutdown log file if one exists.
(If a shutdown log file does not exist, does not create one.) If the
system crashes as a result of a kernel panic, 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, runs in the background. This reduces system boot-up time
by allowing the system to be run with only the primary paging device.
It is possible for dump devices to be used also as paging devices. If
determines that a dump device is already enabled for paging, and that
paging activity has already taken place on that device, a warning mes‐
sage will indicate that the dump may be invalid. If a dump device has
not already been enabled for paging, prevents paging from being enabled
to the device by creating the file does not enable the device for pag‐
ing if the device is locked in (see swapon(1M) for more details). As
finishes saving the image from each dump device, it updates the file
and optionally executes to enable paging on the device.
Options and Operands
The command recognizes the following options and operands.
dirname The name of the existing directory in which to store the crash
dump; the default is
Mark the dump in the dump device as saved, without performing any other
action. The option is useful for manually inhibiting dump
actions called by
Run in the foreground only. By default, runs in the background
when the primary paging device does not contain an unsaved por‐
tion of the crash image. Turning this option on increases sys‐
tem boot-up time, but guarantees that the dump has been saved
when control returns to the caller.
Logs the panic information to
as described above, but does not actually save the dump. The
dump is marked as saved so that future invocations of do not
create duplicate log entries.
Only preserves swap-endangered dump device contents into crash
image files. Swap-endangered dump devices are those devices
that are also configured as swap devices by the system. If all
dump devices are configured as swap devices, the entire dump
will be preserved in the crash directory. If no swap devices
are used as dump devices (dedicated dump devices), only the
file and kernel modules will be copied into the crash direc‐
tory.
Resaves a dump that a previous invocation of
has marked as already saved. This is useful if the first invo‐
cation did ran out of space, and enough space has since been
freed to try again.
Enables additional progress messages and diagnostics.
will compress all physical memory image files and kernel module files
in the dump directory. This option is ignored if the dump image
on the dump device is already compressed. See crashconf(2). In
this case, a warning message will be printed.
will not compress any files in the dump directory.
If neither nor is specified and the amount of free disk space
is less than the total dump size, will compress the image
files.
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 can be used to tell where to find
the dump in the rare instances that doesn't know where to look.
offset is the offset in kBytes, relative to the beginning of the
device specified with 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 can be
used to tell where to find the dump in the rare instances that
doesn't know where to look.
sysfile is the name of a file containing the image of the system that
produced the core dump (which means, it is the system running,
when the crash occurred). If this option is not specified,
uses the /stand/crashconfig/vmunix file. If the file contain‐
ing the image of the system, which caused the crash has
changed, then use this option to specify the new file name.
For complete debugging solution make sure the module directory
is present in the same path as the vmunix.
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 necessary, only part of the dump will be saved to achieve
this requirement. calculates the amount of disk space avail‐
able when it starts saving the dump. Any space used by other
processes while dump is being saved is not taken into account.
minfree may be specified in bytes kilobytes megabytes or giga‐
bytes The default minfree value is zero, and the default unit
is kilobytes.
chunksize
is the size (default kBytes) of a single physical memory image
file before compression. The kByte value must be a multiple of
page size (divisible by 4) and between 64 and 1048576. chunk‐
size may be specified in units of bytes kilobytes megabytes or
gigabytes Larger numbers increase compression efficiency at the
expense of both time and debugging time. If is not specified,
a default is chosen based on the physical memory size and the
amount of available file system space. If the dump image on the
dump device is compressed, 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 compression 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.
tapedevice
is the tape device where the crash dump will be written. Crash
dumps that are written to tape are written using a format. The
crash dump tape can be read using tar(1).
When the option is specified, the option is not allowed and the
whole dump is always preserved. In addition, and are not
allowed and is ignored. Also, when is specified, will not per‐
form any compression.
When dirname is specified with the option, dirname is the name
of the existing directory where the file is created; the
default directory is The file is the first file that is written
out to the dump tape. This file is written a second time once
all the dump files have been written. The first copy of the
file only contains crash dump header information and its file‐
name on tape is It does not contain information for the module
and image files.
When writing to tape, the tape device must be online otherwise
the command will fail with an error. Additionally, when
reaches end-of-tape, it will prompt the user for the next tape.
Any tape errors encountered will result in a generic tape
error.
Defines the interaction between
and opt can be one of the following values:
Do not run from
(default) Call each time finishes saving the image from each
dump device. This option provides the most effi‐
cient use of paging space.
Only call when finishes saving the image file from all dump
devices. If this option is used, no additional
paging space other than the primary paging space is
available until the complete crash dump image is
saved. This option provides a second chance to
retrieve the crash image if fails on first attempt.
For compatibility with earlier syntax, the values of and can be
used in place of and respectively. This usage is obsolescent.
RETURN VALUE
Upon exit, returns the following values:
A crash dump was found and saved,
or has preserved dump information from the primary swap
device and is continuing to run in the background to com‐
plete its tasks.
A crash dump could not be saved due to an error.
No crash dump was found to save.
A partial crash dump was saved, but there was insufficient space
to
preserve the complete dump.
The savecrash process continued in the background, see the file
for actual results.
WARNINGS
relies on the expectation that device numbers have the same meaning
(point to the same devices) at the time the system dumps and at the
time the dump is saved. If, after a crash, the system was booted from
a different boot device in order to run it is possible that this expec‐
tation will not be met. If so, may save an incomplete or incorrect
dump or may fail to save a dump at all. Such cases cannot be reliably
detected, so there may be no warning or error message.
If encounters an error while running in the background (such as running
out of space), it will not be easily detectable by the caller. If the
caller must ensure that the operation was successful, for example
before writing to a dump device, the caller should specify to force to
run in the foreground, and should then examine the exit status of the
process when it finishes.
AUTHOR
was developed by HP and the University of California, Berkeley.
FILES
shutdown log
savecrash startup configuration file
savecrash startup file
crash dump number
default kernel image saved by savecrashSEE ALSOadb(1), tar(1), crashutil(1M), crashconf(1M), swapon(1M).
savecrash(1M)
