08-09-2008
Quote:
Originally Posted by
Annihilannic
That is a very old rule of thumb which I no longer agree with. Memory is so cheap and plentiful these days that you should hardly ever require swap, if you do it is a sign of problems. I generally don't ever configure more than 4GB of swap, even on a 64+GB system.
Yes, I agree with this. The old 2 pounds of swap for every pound of memory was back in the old days when memory was expensive and it was cheaper to use disk swap.
If you have 7 GB of RAM, something is really wrong if you need 14GB of swap.
4GB of swap is more than enough, good post Annihilannic. Thanks.
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LEARN ABOUT POSIX
savecore
savecore(1M) System Administration Commands savecore(1M)
NAME
savecore - save a crash dump of the operating system
SYNOPSIS
/usr/bin/savecore [-Lvd] [-f dumpfile] [directory]
DESCRIPTION
The savecore utility saves a crash dump of the kernel (assuming that one was made) and writes a reboot message in the shutdown log. It is
invoked by the dumpadm service each time the system boots.
savecore saves the crash dump data in the file directory/vmcore.n and the kernel's namelist in directory/unix.n. The trailing .n in the
pathnames is replaced by a number which grows every time savecore is run in that directory.
Before writing out a crash dump, savecore reads a number from the file directory/minfree. This is the minimum number of kilobytes that must
remain free on the file system containing directory. If after saving the crash dump the file system containing directory would have less
free space the number of kilobytes specified in minfree, the crash dump is not saved. if the minfree file does not exist, savecore assumes
a minfree value of 1 megabyte.
The savecore utility also logs a reboot message using facility LOG_AUTH (see syslog(3C)). If the system crashed as a result of a panic,
savecore logs the panic string too.
OPTIONS
The following options are supported:
-d Disregard dump header valid flag. Force savecore to attempt to save a crash dump even if the header information stored on
the dump device indicates the dump has already been saved.
-f dumpfile Attempt to save a crash dump from the specified file instead of from the system's current dump device. This option may be
useful if the information stored on the dump device has been copied to an on-disk file by means of the dd(1M) command.
-L Save a crash dump of the live running Solaris system, without actually rebooting or altering the system in any way. This
option forces savecore to save a live snapshot of the system to the dump device, and then immediately to retrieve the data
and to write it out to a new set of crash dump files in the specified directory. Live system crash dumps can only be per-
formed if you have configured your system to have a dedicated dump device using dumpadm(1M).
savecore -L does not suspend the system, so the contents of memory continue to change while the dump is saved. This means
that live crash dumps are not fully self-consistent.
-v Verbose. Enables verbose error messages from savecore.
OPERANDS
The following operands are supported:
directory Save the crash dump files to the specified directory. If directory is not specified, savecore saves the crash dump
files to the default savecore directory, configured by dumpadm(1M).
FILES
directory/vmcore.n
directory/unix.n
directory/bounds
directory/minfree
/var/crash/'uname -n' default crash dump directory
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO
adb(1), mdb(1), svcs(1), dd(1M), dumpadm(1M), svcadm(1M), syslog(3C), 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 ser-
vice's status can be queried using the svcs(1) command.
If the dump device is also being used as a swap device, you must run savecore very soon after booting, before the swap space containing the
crash dump is overwritten by programs currently running.
SunOS 5.10 25 Sep 2004 savecore(1M)