System Administration Commands dumpadm(1M)
NAME
dumpadm - 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]
DESCRIPTION
The dumpadm program is an administrative command that
manages the configuration 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 message describing
the error is printed to the console. The operating system
then generates a crash dump by writing the contents of phy-
sical memory to a predetermined dump device, which is typi-
cally a local disk partition. The dump device can be config-
ured 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 a pair of files in your file system named unix.X
and vmcore.X, where X is an integer identifying the dump.
Together, these data files form the saved crash dump. The
directory in which the crash dump is saved on reboot can
also be configured using dumpadm.
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 operating system. Thus, no per-
manent 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
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System Administration Commands dumpadm(1M)
Dump content: kernel pages
Dump device: /dev/dsk/c0t0d0s1 (swap)
Savecore directory: /var/crash/saturn
Savecore enabled: yes
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,
and savecore is set to run automatically on reboot.
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 configura-
tion. 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 following:
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.
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System Administration Commands dumpadm(1M)
-d dump-device
Modify the dump configuration to use the specified dump
device. The dump device may 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 config-
ured for both the swap area and the dump device.
-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 specify-
ing kilobytes.
m
A positive integer suffixed with the unit m specify-
ing megabytes.
%
A % symbol, indicating that the minfree value should
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System Administration Commands dumpadm(1M)
be computed 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 alter-
nate 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 par-
tition, 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 speci-
fied, 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 direc-
tory 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
relating 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 settings
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System Administration Commands dumpadm(1M)
from the previous boot must be restored. Your dump con-
figuration is saved in the configuration file for this
purpose. If the configuration file is missing or con-
tains 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.
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
EXIT STATUS
The following exit values are returned:
0
Dump configuration is valid and the specified modifica-
tions, 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.
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System Administration Commands dumpadm(1M)
FILES
/dev/dump
Dump device.
/etc/dumpadm.conf
Contains configuration parameters for dumpadm. Modifi-
able only through that command.
savecore-directory/minfree
Contains minimum amount of free space for savecore-
directory. See savecore(1M).
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWcsr
SEE ALSO
svcs(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
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System Administration Commands dumpadm(1M)
appropriate swap device as the dump device. dumpadm config-
ures 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 dev-
ices 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 administrator 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 adminis-
trator 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 system 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 recommended that alternate
savecore directories also be created with similar permis-
sions, as the operating system crash dump files themselves
may contain secure information.
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