DUMPADM(1M)DUMPADM(1M)NAMEdumpadm - configure operating system crash dump
SYNOPSIS
/usr/sbin/dumpadm [-nuy] [-c content-type] [-d dump-device]
[-m mink | minm | min%] [-s savecore-dir]
[-r root-dir] [-z on | off]
DESCRIPTION
The dumpadm program is an administrative command that manages the con‐
figuration of the operating system crash dump facility. A crash dump is
a disk copy of the physical memory of the computer at the time of a
fatal system error. When a fatal operating system error occurs, a mes‐
sage describing the error is printed to the console. The operating sys‐
tem then generates a crash dump by writing the contents of physical
memory to a predetermined dump device, which is typically a local disk
partition. The dump device can be configured by way of dumpadm. Once
the crash dump has been written to the dump device, the system will
reboot.
Fatal operating system errors can be caused by bugs in the operating
system, its associated device drivers and loadable modules, or by
faulty hardware. Whatever the cause, the crash dump itself provides
invaluable information to your support engineer to aid in diagnosing
the problem. As such, it is vital that the crash dump be retrieved and
given to your support provider. Following an operating system crash,
the savecore(1M) utility is executed automatically during boot to
retrieve the crash dump from the dump device, and write it to the file
system. The directory in which the crash dump is saved on reboot can
also be configured using dumpadm.
When the operating system takes a crash dump the default behavior is to
compress the crash dump. This behavior is controlled by the -z option.
When compression is turned on, the savecore(1M) utility writes one file
to the file system named vmdump.X. If compression is disabled, it
instead writes two files named unix.X and vmcore.X. In the uncompressed
case, both data files form the saved crash dump. In both cases X is an
integer identifying the dump.
For systems with a UFS root file system, the default dump device is
configured to be an appropriate swap partition. Swap partitions are
disk partitions reserved as virtual memory backing store for the oper‐
ating system. Thus, no permanent information resides in swap to be
overwritten by the dump. See swap(1M). For systems with a ZFS root file
system, dedicated ZFS volumes are used for swap and dump areas. For
further information about setting up a dump area with ZFS, see the ZFS
Administration Guide. To view the current dump configuration, use the
dumpadm command with no arguments:
example# dumpadm
Dump content: kernel pages
Dump device: /dev/dsk/c0t0d0s1 (swap)
Savecore directory: /var/crash/saturn
Savecore enabled: yes
Save compressed: on
When no options are specified, dumpadm prints the current crash dump
configuration. The example shows the set of default values: the dump
content is set to kernel memory pages only, the dump device is a swap
disk partition, the directory for savecore files is set to
/var/crash/hostname, savecore is set to run automatically on reboot,
and compression is turned on.
When one or more options are specified, dumpadm verifies that your
changes are valid, and if so, reconfigures the crash dump parameters
and displays the resulting configuration. You must be root to view or
change dump parameters.
OPTIONS
The following options are supported:
-c content-type
Modify the dump configuration so that the crash dump consists of
the specified dump content. The content should be one of the fol‐
lowing:
kernel
Kernel memory pages only.
all
All memory pages.
curproc
Kernel memory pages, and the memory pages of the process whose
thread was currently executing on the CPU on which the crash
dump was initiated. If the thread executing on that CPU is a
kernel thread not associated with any user process, only kernel
pages will be dumped.
-d dump-device
Modify the dump configuration to use the specified dump device. The
dump device may be one of the following:
dump-device
A specific dump device specified as an absolute pathname, such
as /dev/dsk/cNtNdNsN when the system is running a UFS root file
system. Or, specify a ZFS volume, such as
/dev/zvol/dsk/rpool/dump, when the system is running a ZFS root
file system.
swap
If the special token swap is specified as the dump device,
dumpadm examines the active swap entries and selects the most
appropriate entry to configure as the dump device. See
swap(1M). Refer to the NOTES below for details of the algorithm
used to select an appropriate swap entry. When the system is
first installed with a UFS root file system, dumpadm uses the
value for swap to determine the initial dump device setting. A
given ZFS volume cannot be configured for both the swap area
and the dump device.
none
If the special token none is specified, the active dump device
is removed and crash dumps are disabled.
-m mink | minm | min%
Create a minfree file in the current savecore directory indicating
that savecore should maintain at least the specified amount of free
space in the file system where the savecore directory is located.
The min argument can be one of the following:
k
A positive integer suffixed with the unit k specifying kilo‐
bytes.
m
A positive integer suffixed with the unit m specifying
megabytes.
%
A % symbol, indicating that the minfree value should be com‐
puted as the specified percentage of the total current size of
the file system containing the savecore directory.
The savecore command will consult the minfree file, if present,
prior to writing the dump files. If the size of these files would
decrease the amount of free disk space below the minfree threshold,
no dump files are written and an error message is logged. The
administrator should immediately clean up the savecore directory to
provide adequate free space, and re-execute the savecore command
manually. The administrator can also specify an alternate directory
on the savecore command-line.
-n
Modify the dump configuration to not run savecore automatically on
reboot. This is not the recommended system configuration; if the
dump device is a swap partition, the dump data will be overwritten
as the system begins to swap. If savecore is not executed shortly
after boot, crash dump retrieval may not be possible.
-r root-dir
Specify an alternate root directory relative to which dumpadm
should create files. If no -r argument is specified, the default
root directory / is used.
-s savecore-dir
Modify the dump configuration to use the specified directory to
save files written by savecore. The directory should be an absolute
path and exist on the system. If upon reboot the directory does not
exist, it will be created prior to the execution of savecore. See
the NOTES section below for a discussion of security issues relat‐
ing to access to the savecore directory. The default savecore
directory is /var/crash/hostname where hostname is the output of
the -n option to the uname(1) command.
-u
Forcibly update the kernel dump configuration based on the contents
of /etc/dumpadm.conf. Normally this option is used only on reboot
when starting svc:/system/dumpadm:default, when the dumpadm set‐
tings from the previous boot must be restored. Your dump configura‐
tion is saved in the configuration file for this purpose. If the
configuration file is missing or contains invalid values for any
dump properties, the default values are substituted. Following the
update, the configuration file is resynchronized with the kernel
dump configuration.
-y
Modify the dump configuration to automatically run savecore on
reboot. This is the default for this dump setting.
-z on | off
Turns crash dump compression on or off.
EXAMPLES
Example 1 Reconfiguring The Dump Device To A Dedicated Dump Device:
The following command reconfigures the dump device to a dedicated dump
device:
example# dumpadm-d /dev/dsk/c0t2d0s2
Dump content: kernel pages
Dump device: /dev/dsk/c0t2d0s2 (dedicated)
Savecore directory: /var/crash/saturn
Savecore enabled: yes
Save compressed: on
EXIT STATUS
The following exit values are returned:
0
Dump configuration is valid and the specified modifications, if
any, were made successfully.
1
A fatal error occurred in either obtaining or modifying the dump
configuration.
2
Invalid command line options were specified.
FILES
/dev/dump
Dump device.
/etc/dumpadm.conf
Contains configuration parameters for dumpadm. Modifiable only
through that command.
savecore-directory/minfree
Contains minimum amount of free space for savecore-directory. See
savecore(1M).
SEE ALSOsvcs(1), uname(1), savecore(1M), svcadm(1M), swap(1M), attributes(5),
smf(5)NOTES
The system crash dump service is managed by the service management
facility, smf(5), under the service identifier:
svc:/system/dumpadm:default
Administrative actions on this service, such as enabling, disabling, or
requesting restart, can be performed using svcadm(1M). The service's
status can be queried using the svcs(1) command.
Dump Device Selection
When the special swap token is specified as the argument to dumpadm-d
the utility will attempt to configure the most appropriate swap device
as the dump device. dumpadm configures the largest swap block device as
the dump device; if no block devices are available for swap, the
largest swap entry is configured as the dump device. If no swap entries
are present, or none can be configured as the dump device, a warning
message will be displayed. While local and remote swap files can be
configured as the dump device, this is not recommended.
Dump Device/Swap Device Interaction (UFS File Systems Only)
In the event that the dump device is also a swap device, and the swap
device is deleted by the administrator using the swap -d command, the
swap command will automatically invoke dumpadm-d swap in order to
attempt to configure another appropriate swap device as the dump
device. If no swap devices remain or none can be configured as the dump
device, the crash dump will be disabled and a warning message will be
displayed. Similarly, if the crash dump is disabled and the adminis‐
trator adds a new swap device using the swap -a command, dumpadm-d
swap will be invoked to re-enable the crash dump using the new swap
device.
Once dumpadm-d swap has been issued, the new dump device is stored in
the configuration file for subsequent reboots. If a larger or more
appropriate swap device is added by the administrator, the dump device
is not changed; the administrator must re-execute dumpadm-d swap to
reselect the most appropriate device fom the new list of swap devices.
Minimum Free Space
If the dumpadm-m option is used to create a minfree file based on a
percentage of the total size of the file system containing the savecore
directory, this value is not automatically recomputed if the file sys‐
tem subsequently changes size. In this case, the administrator must
re-execute dumpadm-m to recompute the minfree value. If no such file
exists in the savecore directory, savecore will default to a free space
threshold of one megabyte. If no free space threshold is desired, a
minfree file containing size 0 can be created.
Security Issues
If, upon reboot, the specified savecore directory is not present, it
will be created prior to the execution of savecore with permissions
0700 (read, write, execute by owner only) and owner root. It is recom‐
mended that alternate savecore directories also be created with similar
permissions, as the operating system crash dump files themselves may
contain secure information.
Feb 15, 2013 DUMPADM(1M)
