NAME
livedump — a feature that saves operating system state to the file system for debugging purposes.
DESCRIPTION
Live Dump
is a feature by which a running operating system's state can be saved to
the filesystem without stopping/rebooting the system.
The saved dump
can be used for debugging purposes.
Live Dump
saves the information in a existing dump format readable by the system
crash dump access library,
libcrash.
See
libcrash(5).
Live Dump
saves the images and related files in the directory
path/ldump.n.
The trailing
n
in the directory name is a number that increases by one every time
Live Dump
is run with the same
path.
This number is stored in the file
path/lbounds.
If the
lbounds
file does not exist in the configured path then it is created and the
default value of 2 is stored in it.
Live Dump
supports both blocking and non-blocking invocation.
In a blocking invocation, the control will be returned to the
invoker only after
Live Dump
completes.
In case of a non-blocking
invocation, the control will be returned to the callee and the
user can query the status of
Live Dump
by using the
livedump
command.
For blocking mode invocation,
Live Dump
messages will be printed on the user console,
and for non-blocking mode invocation,
Live Dump
messages are stored in the syslog file
/var/adm/syslog/syslog.log.
Live Dump
supports selective dump using page classification similar to crash dump.
Live Dump
uses filesystem space to save the operating system state.
The amount of filesystem space to be left free can be configured by the user.
The operating system state saved by
Live Dump
is in the form of image files.
The maximum size of each image is also configurable by the user.
The location on the filesystem where
Live Dump
saves the system state can be set by the user.
Live Dump
configuration can be queried/changed using the
livedump
utility.
See
livedump(1M)
for more details.
The dump saved by
Live Dump
is not a snapshot of system memory.
Instead it is the state over a period of time.
As the system state keeps changing continuously
(when
Live Dump
is in progress), the dump taken would be a transient one.
Due to this transientness some data structures may be broken
in the dump.
Definitions
- minfree
Amount of space to be left free upon completion of
Live Dump.
If
Live Dump
detects that the free disk space has fallen below
minfree
value, it stops saving the dump.
The saved dump, in this case, may not be debuggable.
- chunksize
Size of a single physical memory image file. See
livedump(1M)
for details.
- pageclass
System memory classes. See
crashconf(2)
for details on defined system memory classes.
Live Dump
does not support saving of the buffer cache and unused pages.
- sid
The session id associated with every
Live Dump
session.
Live Dump
generates this id for each invocation in order to identify a
Live Dump
session uniquely.
The user can use this id to specify the
Live Dump
session to be aborted.
- path
Directory to save the
Live Dump.
If this option is not specified, then
/var/adm/crash
is used as the default directory to save the dump.
AUTHOR
The
Live Dump
feature described here was developed by Hewlett-Packard.
FILES
- /var/adm/syslog/syslog.log
messages saved by
Live Dump
Printable version
